Patent Publication Number: US-2022226070-A1

Title: Cardiac arrhythmia treatment devices and delivery

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of and claims priority to and benefit of U.S. patent application Ser. No. 17/581,543, filed Jan. 21, 2022, which is a continuation of and claims priority to and benefit of U.S. patent application Ser. No. 16/453,932, filed Jun. 26, 2019 and issued Jan. 25, 2022 as U.S. Pat. No. 11,229,500, which is a continuation of and claims priority to and benefit of U.S. patent application Ser. No. 15/644,714, filed Jul. 7, 2017 and issued Aug. 18, 2020 as U.S. Pat. No. 10,743,960 which claims priority to and benefit of U.S. Provisional Patent Application 62/360,110, filed Jul. 8, 2016, and is also a continuation in part of U.S. patent application Ser. No. 14/846,578, filed Sep. 4, 2015, which claims priority to and the benefit of U.S. Provisional Patent Application 62/083,516, filed Nov. 24, 2014, U.S. Provisional Patent Application 62/146,569, filed Apr. 13, 2015, and U.S. Provisional Application 62/045,683, filed Sep. 4, 2014, the disclosures of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     An artificial pacemaker is a medical device that helps control abnormal heart rhythms. A pacemaker uses electrical pulses to prompt the heart to beat at a normal rate. The pacemaker may speed up a slow heart rhythm, control a fast heart rhythm, and coordinate the chambers of the heart. The implantable portions of a pacemaker system generally comprise three main components: a pulse generator, one or more wires called leads, and electrodes found on each lead. The pulse generator produces the electrical signals that make the heart beat. Most pulse generators also have the capability to receive and respond to signals that are sent by the heart. Leads are insulated flexible wires that conduct electrical signals to the heart from the pulse generator. The leads may also relay signals from the heart to the pulse generator. One end of the lead is attached to the pulse generator and the electrode end of the lead is positioned on or in the heart. 
     SUMMARY 
     Methods and apparatuses for use in medical procedures are disclosed. Some implementations may include a medical procedure guide that can overlay portions of anatomy of a patient, where the guide may include alignment markings to facilitate proper placement, procedure markings to facilitate determination of a position at which to commence a medical procedure, and/or imaging markers incorporated within the guide to facilitate commencement or completion of the medical procedure in conjunction with imaging. 
     In some variations, the guide may include critical anatomy markings, or may be flexible to at least partially form to the anatomy of a patient. The guide may be affixed to the patient, for example, with an adhesive, and may be designed to allow for puncture or incision through the guide during a medical procedure. 
     In other implementations, imaging markers may facilitate determination of the position to commence a medical procedure, to facilitate determination of the presence or absence of interposed lung, or to facilitate the determination of a distance between a sternal margin and a thoracic vain or thoracic artery. 
     In some implementations imaging markers may be located at particular known depths within the guide to facilitate completion of the medical procedure. The imaging markers may be radiopaque. 
     In one implementation, the medical procedure may involve insertion of a cardiac therapy lead for pacing or defibrillation and the guide&#39;s alignment markings may be configured to line up with at least a portion of the patient&#39;s sternum and at least one rib. The procedure markings may also be configured to locate a position proximate a lateral margin of the patient&#39;s sternum, in the region of a cardiac notch. The imaging markers may also facilitate determination of a proper depth of insertion for the cardiac therapy lead. In some implementations, the guide may also facilitate a determination of the distance between a posterior surface of a sternum and a pericardium and/or facilitate a determination of the patient&#39;s sternum thickness. 
     The details of one or more variations of the subject matter described herein are set forth in the accompanying drawings and the description below. Other features and advantages of the subject matter described herein will be apparent from the description and drawings, and from the claims. While certain features of the currently disclosed subject matter are described for illustrative purposes in relation to particular implementations, it should be readily understood that such features are not intended to be limiting. The claims that follow this disclosure are intended to define the scope of the protected subject matter. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, show certain aspects of the subject matter disclosed herein and, together with the description, help explain some of the principles associated with the disclosed implementations. In the drawings, 
         FIG. 1  is a front-view of an exemplary pulse generator having features consistent with implementations of the current subject matter; 
         FIG. 2  is a rear-view of an exemplary pulse generator having features consistent with implementations of the current subject matter; 
         FIG. 3  is an illustration of a simplified schematic diagram of an exemplary pulse generator having features consistent with implementations of the current subject matter; 
         FIG. 4A  is an illustration showing exemplary placements of elements of a cardiac pacing system having features consistent with the current subject matter; 
         FIG. 4B  is an illustration showing exemplary placements of elements of a cardiac pacing system having features consistent with the current subject matter; 
         FIG. 4C  is a cross-sectional illustration of a thoracic region of a patient; 
         FIG. 5  is an illustration of an exemplary method of implanting a cardiac pacing system into a patient having features consistent with the current subject matter; 
         FIG. 6A  is an illustration of an exemplary delivery system for a pulse generator having features consistent with implementations of the current subject matter; 
         FIG. 6B  is an illustration of an exemplary delivery system with a pulse generator disposed therein consistent with implementations of the current subject matter; 
         FIG. 7  is an illustration of an exemplary process flow illustrating a method of placing a pacing lead having features consistent with the current subject matter; 
         FIG. 8A  is an illustration of an exemplary lead having features consistent with the current subject matter; 
         FIG. 8B  is an illustration of an exemplary lead having features consistent with the current subject matter; 
         FIG. 9A  is an illustration of the distal end of an exemplary delivery system having features consistent with the current subject matter; 
         FIG. 9B  is an illustration of an exemplary process for using the delivery system illustrated in  FIG. 9A ; 
         FIG. 10  is a schematic illustration of an exemplary delivery control system having features consistent with the current subject matter; 
         FIGS. 11A and 11B  are illustrations of an exemplary lead having features consistent with the current subject matter; 
         FIG. 12  is an illustration of an exemplary sheath for delivering a lead, the sheath having features consistent with the current subject matter; 
         FIG. 13  is an illustration of an intercostal space associated with the cardiac notch of the left lung with an exemplary lead fixation receptacle having features consistent with the current subject matter inserted therein; 
         FIG. 14  is an illustration of an exemplary lead fixation receptacle having features consistent with the current subject matter; 
         FIG. 15  is an illustration of an exemplary lead fixation receptacle having features consistent with the current subject matter; 
         FIG. 16  is an illustration of an exemplary lead fixation receptacle having features consistent with the current subject matter; 
         FIG. 17A  is an illustration of a side view of an exemplary lead delivery system for facilitating delivery of a lead, the lead delivery system having features consistent with the current subject matter; 
         FIG. 17B  is an illustration of a front view of the exemplary lead delivery system illustrated in  FIG. 17A ; 
         FIG. 17C  is an illustration of a top-down view of the exemplary lead delivery system illustrated in  FIG. 17 ; 
         FIG. 18  is an illustration of a schematic diagram showing components of an exemplary lead delivery system having features consistent with the current subject matter; 
         FIG. 19  is an illustration of a medical procedure guide having features consistent with the current subject matter; and, 
         FIG. 20  is an illustration of a medical procedure guide having imaging markers consistent with the current subject matter. 
     
    
    
     When practical, similar reference numbers denote similar structures, features, or elements. 
     DETAILED DESCRIPTION 
     Implantable medical devices (IMDs), such as cardiac pacemakers or implantable cardioverter defibrillators (ICDs), provide therapeutic electrical stimulation to the heart of a patient. This electrical stimulation may be delivered via electrodes on one or more implantable endocardial or epicardial leads that are positioned in or on the heart. This electrical stimulation may also be delivered using a leadless cardiac pacemaker disposed within a chamber of the heart. Therapeutic electrical stimulation may be delivered to the heart in the form of electrical pulses or shocks for pacing, cardioversion or defibrillation. 
     An implantable cardiac pacemaker may be configured to facilitate the treatment of cardiac arrhythmias. The devices, systems and methods of the present disclosure may be used to treat cardiac arrhythmias including, but not limited to, bradycardia, tachycardia, atrial flutter and atrial fibrillation. Resynchronization pacing therapy may also be provided. While embodiments of the present disclosure refer to a cardiac pacing system, is understood that the implantable medical device may additionally be an implantable defibrillator used to treat disruptive cardiac arrhythmias. 
     A cardiac pacemaker consistent with the present disclosure may include a pulse generator implanted adjacent the rib cage of the patient, for example, on the ribcage under the pectoral muscles, laterally on the ribcage, within the mediastinum, subcutaneously on the sternum of the ribcage, and the like. One or more leads may be connected to the pulse generator. A lead may be inserted, for example, between two ribs of a patient so that the distal end of the lead is positioned within the mediastinum of the patient adjacent, but not touching, the heart. The distal end of the lead may include an electrode for providing electrical pulse therapy to the patient&#39;s heart and may also include at least one sensor for detecting a state of the patient&#39;s organs and/or systems. The cardiac pacemaker may include a unitary design where the components of the pulse generator and lead are incorporated within a single form factor. For example, where a first portion of the unitary device resides within the subcutaneous tissue and a second portion of the unitary device is placed through an intercostal space into a location within the mediastinum. 
       FIG. 1  is a front-view  100  of a pulse generator  102  having features consistent with implementations of the current subject matter. The pulse generator  102  may be referred to as a cardiac pacemaker. The pulse generator  102  can include a housing  104 , which may be hermetically sealed. In the present disclosure, and commonly in the art, housing  104  and everything within it may be referred to as a pulse generator, despite there being elements inside the housing other than those that generate pulses (for example, processors, storage, battery, etc.). 
     Housing  104  can be substantially rectangular in shape and the first end of the housing  104  may include a tapered portion  108 . The tapered portion can include a first tapered edge  110 , tapered inwardly toward the transverse plane. The tapered portion  108  can include a second tapered edge  112  tapered inwardly toward the longitudinal plane. Each of the first tapered edge  110  and the second tapered edge  112  may have a similar tapered edge generally symmetrically disposed on the opposite side of tapered portion  108 , to form two pairs of tapered edges. The pairs of tapered edges may thereby form a chisel-shape at the first end  106  of pulse generator  102 . When used in the present disclosure, the term “chisel-shape” refers to any configuration of a portion of housing  104  that facilitates the separation of tissue planes during placement of pulse generator  102  into a patient. The “chisel-shape” can facilitate creation of a tightly fitting and properly sized pocket in the patient&#39;s tissue in which the pulse generator may be secured. For example, a chisel-shape portion of housing  104  may have a single tapered edge, a pair of tapered edges, 2 pairs of tapered edges, and the like. Generally, the tapering of the edges forms the shape of a chisel or the shape of the head of a flat head screwdriver. In some variations, the second end  114  of the pulse generator can be tapered. In other variations, one or more additional sides of the pulse generator  102  can be tapered. 
     Housing  104  of pulse generator  102  can include a second end  114 . The second end  114  can include a port assembly  116 . Port assembly  116  can be integrated with housing  104  to form a hermetically sealed structure. Port assembly  116  may be configured to facilitate the egress of conductors from housing  104  of pulse generator  102  while maintaining a seal. For example, port assembly  116  may be configured to facilitate the egress of a first conductor  118  and a second conductor  120  from housing  104 . The first conductor  118  and the second conductor  120  may combine within port assembly  116  to form a twin-lead cable  122 . In some variations, the twin-lead cable  122  can be a coaxial cable. The twin-lead cable  122  may include a connection port  124  remote from housing  104 . Connection port  124  can be configured to receive at least one lead, for example, a pacing lead. Connection port  124  of the cable  122  can include a sealed housing  126 . Sealed housing  126  can be configured to envelope a portion of the received lead(s) and form a sealed connection with the received lead(s). 
     Port assembly  116  may be made from a different material than housing  104 . For example, housing  104  may be made from a metal alloy and port assembly  116  may be made from a more flexible polymer. While port assembly  116  may be manufactured separately from housing  104  and then integrated with it, port assembly  116  may also be designed to be part of housing  104  itself. The port assembly  116  may be externalized from the housing  104  as depicted in  FIG. 1 . The port assembly  116  may be incorporated within the shape of housing  104  of pulse generator  102 . 
       FIG. 2  is a rear-view  200  of pulse generator  102  showing the back-side  128  of housing  104 . As shown, pulse generator  102  can include one or more electrodes or sensors disposed within housing  104 . As depicted in the example of  FIG. 2 , housing  104  includes a first in-housing electrode  130  and a second in-housing electrode  132 . The various electrodes illustrated and discussed herein may be used for delivering therapy to the patient, sensing a condition of the patient, and/or a combination thereof. A pulse generator consistent with the present disclosure installed at or near the sternum of a patient can monitor the heart, lungs, major blood vessels, and the like through sensor(s) integrated into housing  104 . 
       FIG. 3  is an illustration  300  of a simplified schematic diagram of an exemplary pulse generator  102  having features consistent with the current subject matter. Pulse generator  102  can include signal processing and therapy circuitry to detect various cardiac conditions. Cardiac conditions can include ventricular dyssynchrony, arrhythmias such as bradycardia and tachycardia conditions, and the like. Pulse generator  102  can be configured to sense and discriminate atrial and ventricular activity and then deliver appropriate electrical stimuli to the heart based on a sensed state of the heart. 
     Pulse generator  102  can include one or more components. The one or more components may be hermetically sealed within the housing  104  of pulse generator  102 . Pulse generator  102  can include a controller  302 , configured to control the operation of the pulse generator  102 . The pulse generator  102  can include an atrial pulse generator  304  and may also include a ventricular pulse generator  306 . Controller  302  can be configured to cause the atrial pulse generator  304  and the ventricular pulse generator  306  to generate electrical pulses in accordance with one or more protocols that may be loaded onto controller  302 . Controller  302  can be configured to control pulse generators  304 ,  306 , to deliver electrical pulses with the amplitudes, pulse widths, frequency, or electrode polarities specified by the therapy protocols, to one or more atria or ventricles. 
     Controller electronic storage  308  can store instructions configured to be implemented by the controller to control the functions of pulse generator  102 . 
     Controller  302  can include a processor(s). The processor(s) can include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. The functions attributed to controller  302  herein may be embodied as software, firmware, hardware or any combination thereof. 
     The pulse generator  102  can include a battery  310  to power the components of the pulse generator  102 . In some variations, battery  310  can be configured to charge a capacitor. Atrial pulse generator  304  and ventricular pulse generator  306  can include a capacitor charged by the battery  310 . The electrical energy stored in the capacitor(s) can be discharged as controlled by controller  302 . The electrical energy can be transmitted to its destination through one or more electrode leads  312 ,  314 . The leads can include a ventricular pulsing lead  312 , an atrial pulsing lead  314 , and/or other leads. 
     Pulse generator  102  can include one or more sensors  322 . Sensor(s)  322  can be configured to monitor various aspects of a patient&#39;s physiology. Sensor(s)  322  may be embedded in the housing of pulse generator  102 , incorporated into leads  312 ,  314  or be incorporated into separate leads. Sensors  322  of pulse generator  102  can be configured to detect, for example, signals from a patient&#39;s heart. The signals can be decoded by controller  302  of the pulse generator to determine a state of the patient. In response to detecting a cardiac arrhythmia, controller  302  can be configured to cause appropriate electrical stimulation to be transmitted through electrodes  312  and  314  by atrial pulse generator  304  and/or ventricular pulse generator  306 . 
     Sensor(s)  322  can be further configured to detect other physiological states of the patient, for example, a respiration rate, blood oximetry, and/or other physiological states. In variations where the pulse generator  102  utilizes a plurality of electrodes, controller  302  may be configured to alter the sensing and delivery vectors between available electrodes to enhance the sensitivity and specificity of arrhythmia detection and improve efficacy of the therapy delivered by the electrical impulses from the pulse generator  102 . 
     Pulse generator  102  can include a transceiver  316 . The transceiver can include an antenna  318 . The transceiver  316  can be configured to transmit and/or receive radio frequency signals. The transceiver  316  can be configured to transmit and/or receive wireless signals having any wireless communication protocol. Wireless communication protocols can include Bluetooth, Bluetooth low energy, Near-Field Communication, WiFi, and/or other radio frequency protocols. The transceiver  316  can be configured to transmit and/or receive radio frequency signals to and/or from a programmer  320 . The programmer  320  can be a computing device external to the patient. Programmer  320  may comprise a transceiver configured to transmit and/or receive radio frequency signals to and/or from the transceiver  316  of the pulse generator  102 . Transceiver  316  can be configured to wirelessly communicate with programmer  320  through induction, radio-frequency communication or other short-range communication methodologies. 
     In some variations, programmer  320  can be configured to communicate with the pulse generator  102  through longer-range remote connectivity systems. Such longer-range remote connectivity systems can facilitate remote access, by an operator, to pulse generator  102  without the operator being in close proximity with the patient. Longer-range remote connectivity systems can include, for example, remote connectivity through the Internet, and the like. When an operator connects with pulse generator  102  through longer-range remote connectivity systems, a local device can be positioned within a threshold distance of the patient. The local device can communicate using one or more radio-frequency wireless connections with the pulse generator  102 . The local device can, in turn, include hardware and/or software features configured to facilitate communication between it and an operator device at which the operator is stationed. The local device can be, for example, a mobile computing device such as a smartphone, tablet, laptop, and the like. The local device can be a purpose-built local device configured to communicate with the pulse generator  102 . The local device can be paired with the pulse generator  102  such that the communications between the pulse generator  102  and the local device are encrypted. Communications between the local device and the operator device can be encrypted. 
     Programmer  320  can be configured to program one or more parameters of the pulse generator  102 . The parameter(s) can include timing of the stimulation pulses of the atrial pulse generator, timing of the stimulation pulses of the ventricular pulse generator, timing of pulses relative to certain sensed activity of the anatomy of the patient, the energy levels of the stimulation pulses, the duration of the stimulation pulses, the pattern of the stimulation pulses and other parameters. The programmer  320  can facilitate the performance of diagnostics on the patient or the pulse generator  102 . 
     Programmer  320  can be configured to facilitate an operator of the programmer  320  to define how the pulse generator  102  senses electrical signals, for example ECGs, and the like. The programmer  320  can facilitate an operator of the programmer  320  to define how the pulse generator  102  detects cardiac conditions, for example ventricular dyssynchrony, arrhythmias, and the like. The programmer  320  can facilitate defining how the pulse generator  102  delivers therapy, and communicates with other devices. 
     An operator can fine-tune parameters through the programmer  320 . For example, the sensitivity of sensors embodied in the housing of the pulse generator  302 , or within leads, can be modified. Programmer  320  can facilitate setting up communication protocols between the pulse generator  102  and another device such as a mobile computing device. Programmer  320  can be configured to facilitate modification of the communication protocols of the pulse generator  102 , such as adding security layers, or preventing two-way communication. Programmer  320  can be configured to facilitate determination of which combination of implanted electrodes are best suited for sensing and therapy delivery. 
     Programmer  320  can be used during the implant procedure. For example, programmer  320  can be used to determine if an implanted lead is positioned such that acceptable performance will be possible. If the performance of the system is deemed unacceptable by programmer  320 , the lead may be repositioned by the physician, or an automated delivery system, until the lead resides in a suitable position. Programmer  320  can also be used to communicate feedback from sensors disposed on the leads and housing  104  during the implant procedure. 
     In some cases, concomitant devices such as another pacemaker, an ICD, or a cutaneous or implantable cardiac monitor, can be present in a patient, along with pulse generator  102 . Pulse generator  102  can be configured to communicate with such concomitant devices through transceiver  316  wirelessly, or the concomitant device may be physically connected to pulse generator  102 . Physical connection between devices may be accomplished using a lead emanating from pulse generator  102  that is compatible with the concomitant device. For example, the distal end of a lead emanating from pulse generator  102  may be physically and electrically connected to a port contained on the concomitant device. Physical connection between devices may also be accomplished using an implantable adaptor that facilitates electrical connection between the lead emanating from pulse generator  102  and the concomitant device. For example, an adapter may be used that will physically and electrically couple the devices despite not having native components to facilitate such connection. Concomitant devices may be connected using a “smart adapter” that provides electrical connection between concomitant devices and contains signal processing capabilities to convert signal attributes from each respective device such that the concomitant devices are functionally compatible with each other. 
     Pulse generator  102  can be configured to have a two-way conversation or a one-way conversation with a concomitant device. Controller  302  can be configured to cause the concomitant device to act in concert with pulse generator  102  when providing therapy to the patient, or controller  302  can gather information about the patient from the concomitant device. In some variations, pulse generator  102  can be configured to be triggered via one-way communication from a concomitant device to pulse generator  102 . 
       FIGS. 4A and 4B  are illustrations showing exemplary placements of elements of a cardiac pacing system having features consistent with the present disclosure. Pulse generator  102  can be disposed in a patient, adjacent an outer surface of ribcage  404 . For example, pulse generator  102  can be disposed on the sternum  402  of the patient&#39;s ribcage  404 . A lead  414 , attached to pulse generator  102 , may also be disposed in the patient by traversing through intercostal muscle  410  of the patient. Lead  414  may optionally pass through a receptacle  408  in intercostal muscle  410  to guide the lead, fix the lead, and/or electrically insulate the lead from the tissue of the intercostal muscle  410  (examples of such receptacles are described herein with respect to  FIGS. 13-16 ). 
     In other variations, pulse generator  102  can be disposed outside of a patient&#39;s ribcage in a pectoral position, outside of the patient&#39;s ribcage in a lateral position, below (inferior to) the patient&#39;s ribcage in a subxiphoid or abdominal position, within the patient&#39;s mediastinum, or the like. 
     Lead  414  may be passed through the ribcage so the distal end of the lead and its electrodes are disposed on, or pass through, the inner surface of the rib or inner surface of the innermost intercostal muscle, or may alternatively traverse further within the thoracic cavity, but without physically contacting the tissue comprising the heart. This placement may be referred to herein as intracostal or intracostally. 
     Leads may be inserted between any two ribs within the thoracic cavity, for example, as shown in  FIG. 4A . In some variations, it is desirable to insert the lead through one of the intercostal spaces associated with cardiac notch of the left lung  420 . For example, between the fourth and fifth ribs or between the fifth and sixth ribs. Due to variations in anatomy, the rib spacing associated with the cardiac notch of the left lung  420  may differ. In some patients the cardiac notch of the left lung  420  may not be present or other cardiac anomalies such as dextrocardia may require the insertion through alternative rib spaces. Lead  414  may be inserted into such a location through an incision  406 , as shown in  FIG. 4A . Lead  414  may optionally be inserted into such a location through a receptacle  408 , as shown in  FIG. 4B . 
     Precise placement of a distal end of lead  414 , which may include electrode(s) for defibrillation, pacing or sensing, is now described further with reference to the anatomical illustrations of  FIGS. 4A, 4B and 4C . In some variations, the distal end of lead  414  can be located within the intercostal space or intercostal muscle  410 . In such variations, the distal end of lead  414  is preferably surrounded by a receptacle  408  that electrically insulates the distal end of the lead  414  from the intercostal muscle  410 . In another variation, the distal end of lead  414  may be placed just on or near the inner surface of a rib or on or near the inner surface of the innermost intercostal muscle. In such instances, and in other placements, the lead  414  may include electrical insulation disposed around the electrode. For example, the lead  414  may include an electrode that is insulated on all sides other than one exposed side. This lead configuration can facilitate a placement where the insulated portions of the lead touch the intercostal muscle, or surrounding tissue, while allowing the electrically active portion of the electrode on the lead to be directional (e.g., directed toward the pericardium and the heart). When electrical stimulation is required, the directional electrode emanates the desired electrical stimulation while electrically insulating the surrounding muscle and tissue from the stimulating energy. In some instances, the electrode may be at the distal tip of the lead, and the insulation surrounds the entire circumference of the lead, but leaves exposed the distal tip. In other instances, an electrode located away from the distal tip of the lead may be insulated over a significant portion of the lead&#39;s circumference, for example, approximately 50% or 75% of the circumference may be insulated, leaving only 50% or 25% of the electrode exposed. 
     The distal end of lead  414  can also be positioned so as to abut the parietal pleura of the lung  426 . In other variations, the distal end of lead  414  can be positioned so as to terminate within the mediastinum  428  of the thoracic cavity of the patient, proximate the heart  418 , but not physically in contact with the heart  418  or the pericardium  432  of heart  418 . Alternatively, the distal end of lead  414  can be placed to abut the pericardium  432 , but not physically attach to the epicardial tissue comprising the heart. 
     A portion of lead  414  may be configured to include a preformed particular shape (e.g., including a 45 degree angle bend, a 90 degree angle bend, a coil, or the like) that enables the preformed portion of lead  414  to be directed towards a preferred location as it is inserted into the patient. For example, the distal end of lead  414  may be preformed so it creates an angle of 90 degrees relative to the main body of lead  414 . While lead  414  is being implanted, a sheath or delivery tool may be used to constrain the preformed portion of lead  414  into a straight shape. However, as lead  414  is deployed from the sheath or delivery tool, the preformed portion of lead  414  can revert to its preformed shape. In one instance, the preformed portion of lead  414  reverts to a shape that enables the distal end of lead  414  to reside along and against the posterior surface of the anterior chest wall. Alternatively, a stylet may be used to straighten the preformed shape during the insertion process. Upon removal of the stylet, the preformed shape is again assumed. Any number of preformed shapes are contemplated to facilitate the placement of lead(s) in the positions and particular orientations disclosed herein. 
     The distal end of lead  414  may be physically affixed to cartilage or bone found within the thoracic cavity, for example, to a rib, to cartilage of a rib, or to other bone or cartilage structure in the thoracic cavity. In one variation, the lead can be disposed such that it is wrapped around the patient&#39;s sternum  402  or a patient&#39;s rib. 
     For certain placements, lead  414  can be adequately fixed by direct physical contact with surrounding tissue. In other variations, an additional fixation mechanism may be used at various points along the body of the lead  414 . For example, the distal end of lead  414  can incorporate a fixation mechanism such as a tine, hook, spring, screw, or other fixation device. The fixation mechanism can be configured to secure the lead in the surrounding tissue, cartilage, bone, or other tissue, to prevent the lead from migrating from its original implantation location or orientation. 
       FIG. 5  is an illustration  500  of an exemplary method of implanting a cardiac pacing system into a patient consistent with the present disclosure. At  502 , a pulse generator  102  may be implanted, in a manner described above, adjacent the sternum  402  of a patient. Optionally, pulse generator  102  may be at least partially chisel-shaped to facilitate implantation and the separation of tissue planes. At  504 , a lead  414  may be inserted into an intercostal space  410  of a patient. As described above, lead  414  may optionally be inserted into a receptacle  408  disposed within intercostal space  410 . At  506 , the distal end of lead  414  is delivered to one of a number of suitable final locations for pacing or defibrillation, as described above. 
       FIG. 6A  is an illustration  600  of a pulse generator delivery system  602  for facilitating positioning of pulse generator  102  into a patient, the delivery system  602  having features consistent with the current subject matter.  FIG. 6B  is an illustration  604  of the delivery system  602  as illustrated in  FIG. 6A  with the pulse generator  102  mounted in it. Delivery system  602  can be configured to facilitate implantation of the pulse generator  102  into the thoracic region of a patient. 
     Delivery system  602  includes a proximal end  606  and a distal end  608 . The distal end  608  of delivery system  602  contains a receptacle  610  in which the housing of the pulse generator  102  is loaded. Where the pulse generator  102  contains a connection lead, the delivery system  602  can be configured to accommodate the connection lead so that the connection lead will not be damaged during the implantation of the pulse generator  102 . 
     When pulse generator  102  is fully loaded into delivery system  602 , pulse generator  102  is substantially embedded into the receptacle  610 . In some variations, a portion of the pulse generator  102 &#39;s distal end can be exposed, protruding from the end of receptacle  610 . The tapered shape of the distal end  106  of pulse generator  102  can be used in conjunction with the delivery system  602  to assist with separating tissue planes as delivery system  602  is used to advance pulse generator  102  to its desired location within the patient. 
     In some variations, the entirety of pulse generator  102  can be contained within receptacle  610  of the delivery system  602 . The pulse generator  102  in such a configuration will not be exposed during the initial advancement of delivery system  602  into the patient. The distal end  608  of delivery system  602  may be designed to itself separate tissue planes within the patient as delivery system  602  is advanced to the desired location within the patient. 
     The pulse generator delivery system  602  may be made from a polymer, a metal, a composite material or other suitable material. Pulse generator delivery system  602  can include multiple components. Each component of the pulse generator delivery system  602  can be formed from a material suitable to the function of the component. The pulse generator delivery system  602  can be made from a material capable of being sterilized for repeated use with different patients. 
     Pulse generator delivery system  602  may include a handle  612 . Handle  612  can facilitate advancement of delivery system  602  and pulse generator  102  into a patient&#39;s body. Handle  612  can be disposed on either side of the main body  614  of the delivery system  602 , as illustrated in  FIGS. 6A and 6B . In some variations, handle  612  can be disposed on just one side of the main body  614  of the delivery system  602 . The handle  612  can be configured to be disposed parallel to plane of insertion and advancement  616  of pulse generator delivery system  602  within the body. In some variations, handle  612  can be located orthogonally to the plane of insertion and advancement  616  of the delivery system  602 . Handle  612  can be configured to facilitate the exertion of pressure, by a physician, onto the pulse generator delivery system  602 , to facilitate the advancement and positioning of the delivery system  602  at the desired location within the patient. 
     Pulse generator delivery system  602  can include a pulse generator release device  618 . The release device  618  can be configured to facilitate disengagement of the pulse generator  102  from the delivery system  602 . In some variations, release device  618  can include a plunger  620 . Plunger  620  can include a distal end configured to engage with the proximal end  606  of the pulse generator delivery system  602 . The plunger  620  can engage with the proximal end  606  of the pulse generator delivery system  602  when the pulse generator  102  is loaded into the receptacle  610  of the delivery system  602 . The proximal end  622  of the plunger  620  can extend from the proximal end  606  of the delivery system  602 . 
     Plunger  620  can include a force applicator  624 . Force applicator  624  can be positioned at the proximal end  622  of plunger  620 . Force applicator  624  can be configured to facilitate application of a force to the plunger  620  to advance the plunger  620 . Advancing plunger  620  can force pulse generator  102  from the delivery system  602 . In some variations, the force applicator  624  can be a ring member. The ring member can facilitate insertion, by the physician, of a finger. Pressure can be applied to the plunger  620  through the ring member, forcing the pulse generator  102  out of the receptacle  610  of the delivery system  602  into the patient at its desired location. In some variations, the proximal end  622  of the plunger  620  can include a flat area, for example, similar to the flat area of a syringe, that allows the physician to apply pressure to the plunger  620 . In some variations, the plunger  620  can be activated by a mechanical means such as a ratcheting mechanism. 
     The distal end  608  of the pulse generator delivery device  602  can include one or more sensors. The sensor(s) can be configured to facilitate detection of a state of patient tissues adjacent distal end  608  of the pulse generator delivery device  602 . Various patient tissues can emit, conduct and/or reflect signals. The emitted, conducted and/or reflected signals can provide an indication of the type of tissue encountered by the distal end  608  of the pulse generator delivery device  602 . Such sensor(s) can be configured, for example, to detect the electrical impedance of the tissue adjacent the distal end  608  of the pulse generator delivery device  602 . Different tissues can have different levels of electrical impedance. Monitoring the electrical impedance can facilitate a determination of the location, or tissue plane, of the distal end  608  of the delivery device  602 . 
     In addition to delivery of the pulse generator, delivery of at least one lead for sensing and/or transmitting therapeutic electrical pulses from the pulse generator is typically required. Proper positioning of the distal end of such lead(s) relative to the heart is very important. Delivery systems are provided that can facilitate the insertion of one or more leads to the correct location(s) in the patient. The delivery systems can facilitate finding the location of the initial insertion point for the lead. The initial insertion point optionally being an intercostal space associated with a patient&#39;s cardiac notch of the left lung. The intercostal spaces associated with the cardiac notch commonly include the left-hand-side fourth, fifth and sixth intercostal spaces. Other intercostal spaces on either side of the sternum may be used, especially when the patient is experiencing conditions that prevent use of the fourth, fifth and sixth intercostal spaces, or due to anatomical variations. 
     When making the initial insertion through the epidermis and the intercostal muscles of the patient, it is important to avoid damaging important blood-filled structures of the patient. Various techniques can be employed to avoid damaging important blood-filled structures. For example, sensors can be used to determine the location of the blood-filled structures. Such sensors may include accelerometers configured to monitor pressure waves caused by blood flowing through the blood-filed structures. Sensors configured to emit and detect light-waves may be used to facilitate locating tissues that absorb certain wavelengths of light and thereby locate different types of tissue. Temperature sensors may be configured to detect differences in temperature between blood-filled structures and surrounding tissue. Lasers and detectors may be employed to scan laser light across the surface of a patient to determine the location of subcutaneous blood-filled structures. 
     Conventional medical devices may be employed to locate the desired initial insertion point into the patient. For example, x-ray machines, MRI machines, CT scanning machines, fluoroscopes, ultrasound machines and the like, may be used to facilitate determination of the initial insertion point for the leads as well as facilitate in advancing the lead into the patient. 
       FIG. 19  is an illustration of a medical procedure guide  1910  having features consistent with the current subject matter. 
     Medical procedure guides can be utilized to bolster the reliability of locating a desired point on a patient for performing a medical procedure. For example, a medical procedure can include, for example, inserting or delivering a lead to a portion of an anatomy of a patient. Medical procedure guides can also identify critical structures to be avoided, for example while inserting the lead during the medical procedure. 
     For example, the medical procedure guide  1910  may contain markers or regions on the medical procedure guide  1910  meant to be disposed over anatomical locations on the patient. Once the physician has found those anatomical locations (e.g., the xyphoid process), the physician can place the medical procedure guide  1910  so that the markers or desired regions on the medical procedure guide  1910  correlate with those anatomical locations. With the medical procedure guide  1910  properly positioned on the patient, the physician can then use markings on the medical procedure guide  1910  to locate a desired initial insertion point  1940  or to determine the position at which to commence a medical procedure. The medical procedure guide  1910  can be used with many medical procedures including, but not limited to, insertion of a cardiac therapy lead for pacing or defibrillation. In this way, the medical procedure guide  1910  can be configured to allow for puncture or incision through the guide during the medical procedure. Markings, such as critical anatomy markings, on the medical procedure guide  1910  can also indicate structures to be avoided during the lead delivery process. For example, the medical procedure guide  1910  can be configured to further facilitate a determination of the presence or absence of an interposed lung or facilitate a determination of a distance between a sternal margin and a thoracic vein or a thoracic artery. 
     As used herein, “markings” or “marking regions” refer to marks, recesses, ridges, or other structural features of the medical procedure guide  1910  that are added to the medical procedure guide  1910  (e.g., coloration, changes in opacity, etc.). Markings or marking regions also refer to features that are added to or subtracted from the material that makes up the medical procedure guide  1910 . For example, ridges, scoring, recesses, openings and the like. 
     In some implementations, the medical procedure guide  1910  can have a shape configured to overlay portions of an anatomy of the patient. Portions of the anatomy can include, for example, skin, exposed organs, muscles, tissues, bones, and the like. The shape of the medical procedure guide  1910  can be rectangular, square, circular, oval, or irregular. The medical procedure guide  1910  can be similar to a sheet and have a thickness and an area bounded by a perimeter that overlays the portion of the anatomy. As shown in  FIG. 19 , the thickness of the medical procedure guild  1910  is variable, and that the depiction shows a greater thickness for illustrative purposes. The medical procedure guide  1910  can be flexible and configured to at least partially form to the anatomy of the patient. The medical procedure guide  1910  can be configured to be affixed to the patient, for example by the inclusion of an adhesive applied to a surface of the medical procedure guide  1910 . 
     The medical procedure guide  1910  can also include alignment markings  1920  on the medical procedure guide  1910  to facilitate proper placement of the medical procedure guide  1910  on the patient. As one example, the alignment markings  1920  can be configured to line up with at least a portion of the patient&#39;s sternum and at least one rib. 
     Procedure markings  1940  can also be included on the medical procedure guide  1910  to facilitate determination of a position at which to commence a medical procedure. For example, the procedure markings  1940  can be configured to locate a position proximate the patient&#39;s sternum, in the region of a cardiac notch. 
     Also, imaging markers may be incorporated with the medical procedure guide  1910  to facilitate commencement or completion of the medical procedure in conjunction with imaging. As used herein, “imaging markers” refer to any markers that are added to or otherwise included with medical procedure guide  1910 . A marker can be, in some implementations, an object inserted into or integral with medical procedure guide  1910 . In other implementations, the marker can be a feature such as a dye or other material that can be detected by an imaging device or discerned by the human eye. For example, medical procedure guide  1910  can be used with conventional imaging devices such as CT, x-ray, fluoroscopes, MRI, and the like, that can discern the shape and/or location of imaging markers, such as radiopaque markers. In certain embodiments, the medical procedure guide  1910  may contain markers spaced at known intervals that are visible with the imaging devices. 
       FIG. 20  is an illustration of medical procedure guide  1910  having imaging markers  2010  and  2020  consistent with the current subject matter. 
     In some implementations, imaging markers  2010  can be located at particular known depths within the medical procedure guide  1910  to facilitate completion of the medical procedure. This is illustrated in  FIG. 20 , where imaging markers  2010  are shown at several depths proximate to the procedure marking. The imaging markers  2010  can, for example, facilitate determination of a proper depth of insertion for a cardiac therapy lead, a distance between a posterior surface of a sternum and a pericardium, or the determination of the patient&#39;s sternum thickness. 
     In other implementations, medical procedure guide  1910  can include imaging markers  2020  oriented across the face of guide  1910 , or at a common depth. As shown in  FIG. 20 , imaging markers  2020  may be spaced on the surface of medical procedure guide  1910 . In one implementation, imaging markers  2020  may form a grid pattern, which can facilitate the location of particular anatomy relative to the grid upon imaging. These reference marks can be radiopaque and/or visible, as described herein. The imaging markers  2020  can facilitate locating a position relevant for a medical procedure, for example, locating a position to make a puncture through medical procedure guide  1910  in order to insert a cardiac therapy lead. 
     These imaging markers  2010  (which may be radiopaque markers) may also include a complementing marker that is visible to the eye. Radiopaque markers on or within the medical procedure guide may also be configured to be visible only in certain x-ray or fluoroscopy orientations. For example, certain radiopaque markers can be seen predominantly in a sagittal view, while others radiopaque markers can be predominantly viewed while in an AP (anterior-posterior) view. Such orientation specific radiopaque markings can ensure that medical procedure guide  1910  is properly oriented, but can also provide the ability to obtain positional and thickness measurements for the physician. For example, using medical procedure guide  1910  with x-ray or fluoroscopy, the physician can visualize the rib spacing, the presence or absence of interposed lung, the distance between the posterior surface of the sternum and the pericardium, the distance between the sternal margin to the thoracic vein or artery, and the patient&#39;s sternum thickness. Having this information, the physician can then determine the ideal intercostal spaces for insertion and ultimate placement and orientation of a lead. As another example, the medical procedure guide  1910  may include critical anatomy markings or facilitate the location critical anatomy to avoid damage during a medical procedure. 
     The medical procedure guide  1910  may be used with x-ray or fluoroscopy to obtain measurements for the thickness of the subcutaneous tissue between the surface of the skin and the anterior surface of the sternum. With these measurements, the physician can then determine whether the pulse generator will fit well over the sternum, or if other anatomical locations described above are better suited for the pulse generator placement. Additionally, using the medical procedure guide  1910  to obtain measurements related to the thickness of the sternum, the physician can calculate the minimum insertion depth that is necessary to obtain the entry point into the intracostal space. The physician can additionally determine the insertion depth that is necessary for the particular insertion technique (e.g., surgical, percutaneous, etc.) or lead delivery system, as described in detail below. 
     In one implementation, the medical procedure guide  1910  may consist of a flexible material where the skin facing side of the medical procedure guide  1910  includes a means for temporarily and reversibly adhering to the patient&#39;s skin. The medical procedure guide  1910  is positioned in the desired location as described earlier and then adhered to the patient&#39;s skin. When viewed under x-ray or fluoroscopy, the caretaker can then determine the desired rib space for lead insertion (for example, above the ventricle) and directly correlate the insertion point with the unique marker on the medical procedure guide  1910 . 
     The medical procedure guide  1910  can be a non-sterile tool that can be used prior to sterile preparation of the patient for identifying the proper insertion point. Medical procedure guide  1910  may include any of the aforementioned alignment markings, procedure markings or imaging markers and each may be used to identify particular important locations for a medical procedure. Medical procedure guide  1910  may be designed so that the locations can be identified, for example, by puncturing through guide  1910  and thereby marking the patient, or alternatively by making markings on the patient adjacent to guide  1910 , or within openings in guide  1910 . Medical procedure guide  1910  may consist of a thin sterile barrier material, that once properly oriented, is placed on the patient within the sterile field. The medical procedure guide  1910  is adhered to the patient&#39;s skin and can remain in place throughout the lead insertion process. In this application, the medical procedure guide  1910  material has properties allowing for an incision by scalpel, needle or the like, to be made directly through the medical procedure guide  1910 &#39;s sterile barrier material. As described above, the sterile barrier medical procedure guide  1910  may contain unique visible and radiopaque markers to assist with placement, orientation, and lead insertion. 
     Advancing a lead into a patient can also present the risk of damaging physiological structures of the patient. Sensors may be employed to monitor the characteristics of tissues within the vicinity of the distal end of an advancing lead. Readings from sensors associated with the characteristics of tissues can be compared against known characteristics to determine the type of tissue in the vicinity of the distal end of the advancing lead. 
     Sensors, such as pH sensors, thermocouples, accelerometers, electrical impedance monitors, and the like, may be used to detect the depth of the distal end of the electrode in the patient. Physiological characteristics of the body change the further a lead ventures into it. Measurements performed by sensors at, or near, the distal end of the advancing lead may facilitate the determination of the type of tissue in the vicinity of the distal end of the lead, as well as its depth into the patient. 
     Various medical imaging procedures, may be used on a patient to determine the location of the desired positions in the heart for the distal end of the lead(s). This information can be used, in conjunction with sensor readings, of the kind described herein, to determine when the distal end of the lead has advanced to a desired location within the patient. 
     Components may be used to first create a channel to the desired location for the distal end of the lead. Components can include sheathes, needles, cannulas, balloon catheters and the like. A component may be advanced into the patient with the assistance of sensor measurements to determine the location of the distal end of the component. Once the component has reached the desired location, the component may be replaced with the lead or the lead may be inserted within the component. An example of a component can include an expandable sheath. Once the sheath has been advanced to the desired location, a cannula extending the length of the sheath may be expanded, allowing a lead to be pass through the cannula. The sheath may then be removed from around the lead, leaving the lead in situ with the distal end of the lead at the desired location. 
     Determination of the final placement of the distal end of a lead is important for the delivery of effective therapeutic electrical pulses for pacing the heart. The present disclosure describes multiple technologies to assist in placement of a lead in the desired location. For example, the use of sensors on the pulse generator, on the distal end of leads, or on delivery components. In addition, when a lead or component is advanced into a patient, balloons may be employed to avoid damaging physiological structures of the patient. Inflatable balloons may be disposed on the distal end of the lead or component, on the sides of a lead body of the lead, or may be circumferentially disposed about the lead body. The balloons may be inflated to facilitate the displacement of tissue from the lead to avoid causing damage to the tissue by the advancing lead. A lead delivery assembly may also be used to facilitate delivery of the lead to the desired location. In some variations, the lead delivery assembly may be configured to automatically deliver the distal end of the lead to the desired location in the patient. 
       FIG. 7  is an illustration  700  of an exemplary process flow illustrating a method of delivering a lead having features consistent with the present disclosure. At  702 , the location of blood-filled structures, in the vicinity of an intercostal space, can be determined. The intercostal space can be an intercostal space associated with the cardiac notch of the patient. Determining the location of the blood-filed structures may be facilitated by one or more sensors configured to detect the location of blood-filled structures. 
     At  704 , a region can be chosen for advancing of a lead through intercostal muscles associated with the cardiac notch. The region chosen may be based on the determined location of blood-filled structures of the patient in that region. It is important that damage to blood-filled structures, such as arteries, veins, and the like, is avoided when advancing a lead into a patient. 
     At  706 , a lead can be advanced through the intercostal muscles associated with the cardiac notch of the patient. Care should be taken to avoid damaging important physiological structures. Sensors, of the kind described herein, may be used to help avoid damage to important physiological structures. 
     At  708 , advancement of the lead through the intercostal muscles can be ceased. Advancement may be ceased in response to an indication that the distal end of the lead has advanced to the desired location. Indication that the distal end of the lead is at the desired location may be provided through measurements obtained by one or more sensors of the kind described herein. 
     The lead advanced through the intercostal muscles associated with the cardiac notch of the patient can be configured to transmit therapeutic electrical pulses to pace or defibrillate the patient&#39;s heart.  FIG. 8A  is an illustration  800   a  of an exemplary lead  802  having features consistent with the present disclosure. For the lead to deliver therapeutic electrical pulses to the heart for pacing or defibrillating the heart, a proximal end  804  of lead  802  is configured to couple with the pulse generator  102 . The proximal end  804  of lead  802  may be configured to couple with a connection port  124 . The connection port can be configured to couple the proximal end  804  of lead  802  to one or more conductors, such as conductors  118  and  120 . When the proximal end  804  of lead  802  couples with connection port  124 , a sealed housing may be formed between them. In some variations, the materials of connection port  124  and the proximal end  804  of lead  802  may be fused together. In some variations, the proximal end  804  of lead  802  may be configured to be pushed into the sealed housing  126 , or vice versa. Optionally, the external diameter of the inserted member may be slightly greater than the internal diameter of the receiving member causing a snug, sealed fit between the two members. Optionally, a mechanism, such as a set-screw or mechanical lock, may be implemented upon the connection port  124  or proximal lead end  804  in order to prevent unintentional disconnection of the lead  802  from pulse generator  102 . 
     Also shown in  FIG. 8A  is the distal end  806  of lead  802 . The distal end  806  of lead  802  may comprise an electrode  808 . In some variations, lead  802  may include a plurality of electrodes. In such variations, lead  802  may include a multiple-pole lead. Individual poles of the multiple-pole lead can feed into separate electrodes. Electrode  808  at the distal end  806  of lead  802  may be configured to deliver electrical pulses to pace or defibrillate the heart when located in the desired position for pacing the heart. Electrodes used for sensing cardiac activity may be oriented on one side of the distal end  806  of lead  802  so that they are facing towards the pericardium and heart, and away from the skeletal muscles in the anterior chest wall and/or surrounding intracostal tissue. Electrodes used for sensing extracardiac activity may be oriented on one or both sides of the distal end  806  of lead  802  or circumferentially around the lead  802 . In certain applications, directing electrodes away from the pericardial surface can result in enhanced sensing of extracardiac signals. 
     The distal end  806  of lead  802  can include one or more sensors  810 . Sensor(s)  810  can be configured to monitor physiological characteristics of the patient while the distal end  806  of lead  802  is being advanced into the patient. Sensors can be disposed along the length of lead  802 . For example, sensor  812  is disposed some distance from the distal end  806 . In such example, sensor  812  may reside in the subcutaneous tissue between the anterior surface of the ribcage and the surface of the skin, providing unique sensing from such a location. Such sensors incorporated onto the lead can detect subtle physiological, chemical and electrical differences that distinguish the lead&#39;s placement within the desired location, as opposed to other locations in the patient&#39;s thoracic cavity. 
     In some variations, the proximal end  804  of lead  802  may be coupled with pulse generator  102  prior to the distal end  806  of lead  802  being advanced through the intercostal space of the patient. In some variations, the proximal end  804  of the lead  802  may be coupled with pulse generator  102  after the distal end  806  of lead  802  has been advanced to the desired location. 
     To assist in the placement of the lead, various medical instruments may be used. The medical instruments may be used alone, or in combination with sensors disposed on the lead that is being placed. Medical instruments may be used to help the physician to access the desired location for the placement of a lead and/or confirm that the distal end of the lead has reached the desired location. For example, instruments, such as an endoscope or laparoscopic camera, with its long, thin, flexible (or rigid) tube, light and video camera can assist the physician in confirming that the distal end  806  of lead  802  has reached the desired location within the thoracic cavity. Other tools known to one skilled in the art such as a guidewire, guide catheter, or sheath may be used in conjunction with medical instruments, such as the laparoscopic camera, and may be advanced alongside and to the location identified by the medical instruments. Medical instruments such as a guidewire can be advanced directly to the desired location for the distal end of the lead with the assistance of acoustic sound, ultrasound, real-time spectroscopic analysis of tissue, real-time density analysis of tissue or by delivery of contrast media that may be observed by real-time imaging equipment. 
     In some variations, the patient may have medical devices previously implanted that may include sensors configured to monitor physiological characteristics of the patient. The physiological characteristics of the patient may change based on the advancement of the lead through the intercostal space of the patient. The previously implanted medical device may have sensors configured to detect movement of the advancing lead. The previously implanted medical device can be configured to communicate this information back to the physician to verify the location of the advancing lead. 
     Sensors disposed on the lead, such as sensors  810  disposed on distal end  806  of the lead may be used to facilitate the delivery of the lead to the desired location. Sensor(s)  810  can be configured to facilitate determination of a depth of the distal end  806  of lead  802 . As described above, the depth of the desired location within the patient can be determined using one or more medical instruments. This can be determined during implantation of the lead  802  or prior to the procedure taking place. 
     Although sensor(s)  810  is illustrated as a single element in  FIG. 8A , sensor(s)  810  can include multiple separate sensors. The sensors  810  can be configured to facilitate placement of the distal end  806  of the lead  802  at a desired location and verification thereof. 
     Sensor(s)  810  can be configured to transmit sensor information during advancement to the desired location. Sensor(s)  810  may transmit signals associated with the monitored physiological characteristics of the tissue within the vicinity of the distal end  806  of the lead  802 . In some variations, the signals from sensor(s)  810  may be transmitted to a computing device(s) configured to facilitate placement of the lead  802  in the desired location. In such variations, the computing device(s) can be configured to assess the sensor information individually, or in the aggregate, to determine the location of the distal end  806  of lead  802 . The computing device(s) can be configured to present alerts and/or instructions associated with the position of the distal end  806  of lead  802 . 
     In some variations, lead  802  can be first coupled with connection port  124  of pulse generator  102 . Signals generated by sensor(s)  810  can be transmitted to a computing device(s) using transceiver  316  in pulse generator  102 , as illustrated in  FIG. 3 . 
     An accelerometer may be used to facilitate delivery of the distal end  806  of lead  802  to the desired location. An accelerometer may be disposed at the distal end  806  of lead  802 . The accelerometer may be configured to monitor the movement of the distal end  806  of lead  802 . The accelerometer may transmit this information to a computing device or the physician. The computing device, or the physician, can determine the location of the distal end  806  of the lead  802  based on the continuous movement information received from the accelerometer as the lead  802  is advanced into the patient. The computing device or the physician may know the initial entry position for lead  802 . The movement information can indicate a continuous path taken by the lead  802  as it advanced into the body of the patient, thereby providing an indication of the location of the distal end  806  of lead  802 . Pressure waves from the beating heart may differ as absorption changes within deepening tissue planes. These pressure wave differences may be used to assess the depth of the distal end of the electrode. 
     The accelerometer can also be configured to monitor acoustic pressure waves generated by various anatomical structures of the body. For example, the accelerometer can be configured to detect acoustic pressure waves generated by the heart or by other anatomical structures of the body. The closer the accelerometer gets to the heart, the greater the acoustic pressure waves generated by the heart will become. By comparing the detected acoustical pressure waves with known models, a location of the distal end  806  of lead  802  can be determined. 
     Pressure waves or vibrations can be artificially generated to cause the pressure waves or vibrations to traverse through the patient. The pressure waves or vibrations can be generated in a controlled manner. The pressure waves or vibrations may be distorted as they traverse through the patient. The level of type of distortion that is likely to be experienced by the pressure waves or vibrations may be known. The pressure waves or vibrations detected by the accelerometer can be compared to the known models to facilitate determination or verification of the location of the distal end  806  of lead  802 . 
     Different tissues within a body exhibit different physiological characteristics. The same tissues situated at different locations within the body can also exhibit different physiological characteristics. Sensors, disposed on the distal end  806 , of lead  802  can be used to monitor the change in the physiological characteristics as the distal end  806  is advanced into the body of the patient. For example, the tissues of a patient through which a lead is advanced can demonstrate differing resistances, physiological properties, electrical impedance, temperature, pH levels, pressures, and the like. These different physiological characteristics, and the change in physiological characteristics, experienced as a sensor traverses through a body can be known or identified. For example, even if the actual degree is not known ahead of time, the change in sensor input when the sensor traverses from one tissue media to another may be identifiable in real-time. Consequently, sensors configured to detect physiological characteristics of a patient can be employed to facilitate determining and verifying the location of the distal end  806  of lead  802 . 
     Different tissues can exhibit different insulative properties. The insulative properties of tissues, or the change in insulative properties of tissues, between the desired entry-point for the lead and the desired destination for the lead can be known. Sensor  810  can include an electrical impedance detector. An electrical impedance detector can be configured to monitor the electrical impedance of the tissue in the vicinity of the distal end  806  of lead  802 . The electrical impedance of the tissue monitored by the electrical impedance detector can be compared with the known insulative properties of the tissues between the entry point and the destination, to determine the location of the distal end of lead  802  or a transition from one tissue plane to another may be recognized by a measurable change in the measured impedance. 
     Varying levels of electrical activity can be experienced at different locations with the body. Electrical signals emitted from the heart, or other muscles can send electrical energy through the body. This electrical energy will dissipate the further it gets from its source. Various tissues will distort the electrical energy in different ways. Sensors configured to detect the electrical energy generated by the heart and/or other anatomical structures can monitor the electrical energy as the lead is advanced. By comparing the monitored electrical energy with known models, a determination or verification of the location of the distal end  806  of lead  802  can be made. The sensors may be configured to identify sudden changes in the electrical activity caused by advancement of the sensor into different tissue planes. 
     Tissues throughout the body have varying pH levels. The pH levels of tissues can change with depth into the body. Sensor(s)  810  can include a pH meter configured to detect the pH levels of the tissue in the vicinity of the sensor(s)  810  as the sensor(s) advance through the patient. The detected pH levels, or detected changes in pH levels, can be compared with known models to facilitate determination or verification of the location of the distal end  806  of lead  802 . The pH meter may be configured to identify sudden changes in the pH level caused by advancement of the meter into different tissue planes. 
     Different tissues can affect vibration-waves or sound-waves in different ways. Sensor(s)  810  can include acoustic sensors. The acoustic sensors can be configured to detect vibration waves or sound waves travelling through tissues surrounding sensor(s)  810 . The vibration waves can be emitted by vibration-emitting devices embedded the lead  802 . The vibration waves can be emitted by vibration-emitting devices located on a hospital gurney, positioned on the patient, or otherwise remote from lead  802 . Sensor(s)  810  can be configured to transmit detected vibration-wave information to a computing device configured to determine the location of the distal end  806  of lead  802  based on the detected vibration-wave information. 
     Different tissues can have different known effects on the emitted electromagnetic waves. Sensors can be used to detect the effect that the tissue in the vicinity of the sensors have on the electromagnet waves. By comparing the effect that the tissue has on the electromagnetic waves with known electromagnetic effects, the identity of the tissue can be obtained and the location of the lead can be determined or verified. For example, sensor(s)  810  can include electromagnetic wave sensors. Electromagnetic wave sensors can include an electromagnetic wave emitter and an electromagnetic wave detector. The electromagnetic waves will be absorbed, reflected, deflected, and/or otherwise affected by tissue surrounding sensor(s)  810 . Sensor(s)  810  can be configured to detect the change in the reflected electromagnetic waves compared to the emitted electromagnetic waves. By comparing the effect the tissue in the vicinity of the sensor(s)  810  has on the electromagnetic waves with known models, a determination verification of the location of lead  802  can be made. The sensors may be configured to identify sudden changes in the electromagnetic activity caused by advancement of the sensor into different tissue planes. 
       FIG. 9A  is an illustration  900  of the distal end of an exemplary delivery system  902  having features consistent with the presently described subject matter. While  FIG. 9A  is described with reference to a delivery system, one of ordinary skill in the art can appreciate and understand that the technology described herein could be applied directly to the end of a lead, such as lead  802 . The present disclosure is intended to apply to a delivery system, such as delivery system  902 , as well as a lead, such as lead  802 . 
     Delivery system  902  can facilitate placement of the distal end of a lead, such as lead  802  illustrated in  FIG. 8 , to a desired location by use of electromagnetic waves, such as light waves. Delivery system  902  may comprise a delivery catheter body  904 . Delivery catheter body  904  may be configured to facilitate advancement of delivery catheter body  904  into the patient to a desired location. The distal tip  906  of delivery catheter body  904  may comprise a light source  908 . Light source  908  can be configured to emit photons having a visible wavelength, infrared wavelength, ultraviolet wavelength, and the like. Delivery catheter body  904  may comprise a light detector  910 . Light detector  910  may be configured to detect light waves, emitted by the light source  908 , reflected by tissues surrounding distal tip  906  of delivery catheter body  904 . 
       FIG. 9B  is an illustration  912  of an exemplary process for using the delivery system illustrated in  FIG. 9A . Light detector  910  can be configured to detect light waves reflected by the tissue adjacent the distal end  906  of delivery system  902 . Information associated with the detected light waves may be transmitted to a computing device. The computing device can be configured to interpret the information transmitted from light detector  910  and determine a difference between the light emitted and the light detected. 
     At  914 , light source  908  can be activated. Light source  908  may emit light-waves into the tissue in the general direction of the intended advancement of delivery system  902 . At  916 , the tissue can absorb a portion of the emitted light waves. At  918 , light detector  910  can detect the reflected light waves, reflected by tissues surrounding light source  908 . At  920 , a determination of a change in the absorption of the light waves by tissues surrounding the distal tip  906  of delivery system  902  can be made. 
     At  922 , in response to an indication that the absorption of light waves has not changed, delivery system  902  can be configured to advance a delivery system, such as delivery system  902 , into the patient. In some variations, a physician can advance delivery system  902  into the patient. In other variations, the delivery system  902  can be advanced into the patient automatically. 
     At  924 , in response to an indication that the absorption of light waves has changed, an alert can be provided to the physician. In some variations, the alert can be provided to the physician through a computing device configured to facilitate positioning of delivery system  902  into the patient. 
     In some variations, a computing device may be configured to facilitate positioning of delivery system  902  into the patient. The computing device can be configured to alert the physician to the type of tissue in the vicinity of distal tip  906  of delivery system  902 . In some variations, the computing device can be configured to alert the physician when the distal tip  906  reaches a tissue having characteristics consistent with the desired location of the distal tip  906  of delivery system  902 . For example, when the characteristics of the tissue in the vicinity of the distal tip  906  match those within the intercostal tissues, or a particular location within the medistiunum, an alert may be provided. 
     Blood vessels, both venous and arterial, absorb red, near infrared and infrared (IR) light waves to a greater degree than surrounding tissues. When illuminating the surface of the body with red, near infrared and infrared (IR) light waves, blood rich tissues, for example veins, will absorb more of this light than other tissues, and other tissues will reflect more of this light than the blood rich tissues. Analysis of the pattern of reflections can enable the blood rich tissues to be located. A positive or negative image can be projected on the skin of the patient at the location of the vein. In some variations, the vein can be represented by a bright area and the absence of a vein can be represented as a dark area, or vice versa. 
     Delivery system  902  can include a subcutaneous visualization enhancer. The subcutaneous visualization enhancer may be configured to enhance visualization of veins, arteries, and other subcutaneous structures of the body. The subcutaneous visualization enhancer can include moving laser light sources to detect the presence of blood-filled structures, such as venous or arterial structures below the surface of the skin. The subcutaneous visualization enhancer can include systems configured to project an image onto the surface of the skin that can show an operator the pattern of the detected subcutaneous blood-filled structures. Laser light from laser light sources can be scanned over the surface of the body using mirrors. A light detector can be configured to measure the reflections of the laser light and use the pattern of reflections to identify the targeted blood rich structures. 
     Such subcutaneous visualization enhancers can be used to facilitate determination of the location for the initial approach for inserting a lead, such as lead  802 , through the intercostal space associated with the cardiac notch of the patient. In some variations, the visualization enhancers can be disposed remote from the delivery system and/or can be configured to enhance visualization enhancers disposed on the delivery system. 
     With the provision of a visualization of the detected subcutaneous structures, the physician can assess the position of subcutaneous structures such as the internal thoracic artery, or other structures, of the body while concurrently inserting components of the delivery system into the body, while avoiding those subcutaneous structures. 
     In some variations, during advancement of lead  802  through the intercostal space associated with the cardiac notch, sensor(s)  810  can be configured to transmit obtained readings to a computing device for interpretation. In some variations, the computing device is pulse generator  102 . In some variations, pulse generator  102  is used to transmit the readings to an external computing device for interpretation. In any event, the sensor information from the various sensors can be used individually, or accumulatively, to determine the location of the distal end of lead  802 . 
       FIG. 10  is a schematic illustration of a delivery control system  1000  having features consistent with the current subject matter. The delivery control system  1000  can be configured to automatically deliver a lead to the desired position within the patient. For example, the delivery control system  1000  can be configured to automatically deliver a distal tip of a lead through the intercostal space associated with the cardiac notch. 
     Delivery control system  1000  can be configured to receive a plurality of inputs. The inputs can come from one or more sensors disposed in, or on, the patient. For example, delivery control system  1000  can be configured to receive subcutaneous structure visualization information  1002 , information associated with delivery insertion systems  1004 , information associated with sensors  1006 , and the like. 
     Delivery control system  1000  can be configured to use remote sensors  1006  to facilitate determination of the insertion site for the lead. Sensors  1006  can be disposed in various instruments configured to be inserted into the patient. Sensors  1006  can also be disposed in various instruments configured to remain external to the patient. 
     Delivery control system  1000  can be configured to perform depth assessments  1008 . The depth assessments  1008  can be configured to determine the depth of the distal end of an inserted instrument, such as a lead  802  illustrated in  FIG. 8A . Depth assessments  1008  can be configured to determine the depth of the distal end of the inserted instrument through light detection systems  1010 , pressure wave analysis  1012 , acoustic analysis, and the like. 
     Depth assessments  1008  can be configured to determine the depth of the delivery system, or lead, though pressure wave analysis systems  1012 . Pressure waves can be detected by accelerometers as herein described. 
     Depth assessments  1008  can be configured to determine the depth of the delivery system though acoustic analysis systems  1014 . Acoustic analysis system  1014  can be configured to operate in a similar manner to a stethoscope. The acoustic analysis system  1014  can be configured to detect the first heart sound (S1), the second heart sound (S2), or other heart sounds. Based on the measurements obtained by the acoustic analysis system  1014 , a depth and/or location of the distal end of a delivery system and/or inserted medical component can be determined. The acoustic analysis system  1014  can be configured to measure the duration, pitch, shape, and tonal quality of the heart sounds. By comparing the duration, pitch, shape, and tonal quality of the heart sounds with known models, a determination or verification of the location of the lead can be made. Sudden changes in the degree of heart sounds may be used to indicate advancement into a new tissue plane. 
     In some variations, the lead can include markers or sensors that facilitate the correct placement and orientation of the lead. Certain markers such as a visual scale, radiopaque, magnetic, ultrasound markers, and the like, can be position at defined areas along the length of the lead so that the markers can be readily observed by an implanting physician, or automated system, on complementary imaging instruments such as fluoroscopy, x-ray, ultrasound, or other imaging instruments known in the art. Through the use of these markers, the physician, or automated implantation device, can guide the lead to the desired location within the intercostal muscle, pleural space, mediastinum, or other desired position, as applicable, and also ensure the correct orientation. 
     Avoiding damage to tissues in the vicinity of the path-of-travel for the lead is important. Moving various tissues from the path of the lead without damaging them is also important.  FIGS. 11A and 11B  are illustrations  1100  and  1102  of an exemplary lead  802  having features consistent with the present disclosure for moving and avoiding damage to tissues during lead delivery. Lead  802  can comprise a distal tip  1104 . Distal tip  1104  can include at least one electrode and/or sensor  1106 . 
     Having leads directly touch the tissue of a patient can be undesirable and can damage the tissue. Consequently, the distal tip  1104  of lead  802  can include an inflatable balloon  1108 . Balloon  1108  can be inflated when the distal tip  1104  of lead  802  encounters an anatomical structure obstructing its path, or prior to moving near sensitive anatomy during lead delivery. The balloon may be configured to divert the obstacle and/or the lead to facilitate circumventing the anatomical structure or may indicate that the lead has reached its intended destination. 
     To inflate the balloon, lead  802  can include a gas channel  1110 . At the end of gas channel  1110  there can be a valve  1112 . Valve  1112  can be controlled through physical manipulation of a valve actuator, through electrical stimulation, through pressure changes in gas channel  1110  and/or controlled in other ways. In some variations, the valve  1112  may be configured at the proximal end of the lead  802 . 
     When positioning lead  802  into a patient, lead  802  may cause damage to, or perforations of, the soft tissues of the patient. When lead  802  is being installed into a patient, distal tip  1104  of lead  802  can encounter soft tissue of the patient that should be avoided. In response to encountering the soft tissue of the patient, gas can be introduced into gas channel  1110 , valve  1112  can be opened and balloon  1108  can be inflated, as shown in  FIG. 11B . Inflating balloon  1108  can cause the balloon to stretch and push into the soft tissue of the patient, moving the soft tissue out of the way and/or guiding distal tip  1104  of lead  802  around the soft tissue. When distal tip  1104  of lead  802  has passed by the soft tissue obstruction, valve  1112  can be closed and the balloon deflated. 
     In some variations, a delivery component or system is used to facilitate delivery of a lead, such as lead  802 , to the desired location.  FIG. 12  is an illustration  1200  of an exemplary delivery system for a lead having features consistent with the present disclosure. An example of the delivery system is an expandable sheath  1202 . Expandable sheath  1202  can be inserted into the patient at the desired insertion point, identified using one or more of the technologies described herein. Expandable sheath  1202  can include a tip  1204 . In some variations, tip  1204  may be radiopaque. A radiopaque tip  1204  may be configured to facilitate feeding of the expandable sheath  1202  to a desired location using one or more radiography techniques known in the art and described herein. Such radiography techniques can include fluoroscopy, CT scan, and the like. 
     Tip  1204  can include one or more sensors for facilitating the placement of the lead. The sensors included in tip  1204  of the expandable sheath  1202  can be the same or similar to the sensors described herein for monitoring physiological characteristics of the body and other characteristics for facilitating positioning of a lead in a body. 
     Expandable sheath  1202  can include a channel  1206  running through a hollow cylinder  1208  of expandable sheath  1202 . When tip  1204  of expandable sheath  1202  is at the desired location, gas or liquid can be introduced into hollow cylinder  1208 . The gas or liquid can be introduced into hollow cylinder  1208  through a first port  1210 . Hollow cylinder  1208  can expand, under the pressure of the gas or liquid, causing channel  1206  running through hollow cylinder  1208  to increase in size. A lead, such as lead  802  illustrated in  FIG. 8A , can be inserted into channel  1206  through a central port  1212 . Hollow cylinder  1208  can be expanded until channel  1206  is larger than the lead. In some variations, channel  1206  can be expanded to accommodate leads of several French sizes. Once the lead is in the desired place, expandable sheath  1202  can be removed, by allowing the lead to pass through channel  1206 . In some variations, liquid or gas can be introduced into or removed from channel  1006  through a second port  1214 . 
     Using expandable sheath  1202  can provide an insertion diameter smaller than the useable diameter. This can facilitate a reduction in the risk of damage to tissues and vessels within the patient when placing the lead. 
     When electricity is brought within the vicinity of muscle tissue, the muscle will contract. Consequently, having a lead for carrying electrical pulses traversing through intercostal muscle tissue may cause the intercostal muscle tissue to contract. Electrical insulation can be provided in the form of a receptacle disposed in the intercostal muscle, where the receptacle is configured to electrically insulate the intercostal muscle from the lead. 
       FIG. 13  is an illustration  1300  of an intercostal space  1302  associated with the cardiac notch of the left lung with an exemplary lead receptacle  1304  having features consistent with the present disclosure. Lead receptacle  1304  can facilitate the placement of leads, and/or other instruments and avoid the leads and/or instruments physically contacting the intercostal tissue. When the distal end of the lead is positioned to terminate in the intercostal muscle, the lead can be passed through lead receptacle  1304  that has been previously placed within the patient&#39;s intercostal muscles. Lead receptacle  1304  can be configured to be electrically insulated so that electrical energy emanating from the lead will not stimulate the surrounding intercostal and skeletal muscle tissue, but will allow the electrical energy to traverse through and stimulate cardiac tissue. 
     The intercostal space  1302  is the space between two ribs, for example, rib  1306   a  and rib  1306   b . Intercostal muscles  1308   a ,  1308   b  and  1308   c  can extend between two ribs  1306   a  and  1306   b , filling intercostal space  1302 . Various blood vessels and nerves can run between the different layers of intercostal muscles. For example, intercostal vein  1310 , intercostal artery  1312 , the intercostal nerve  1314  can be disposed under a flange  1316  of upper rib  1306   a  and between the innermost intercostal muscle  1308   c  and its adjacent intercostal muscle  1308   b . Similarly, collateral branches  1318  can be disposed between the innermost intercostal muscle  1308   c  and its adjacent intercostal muscle  1308   b.    
     The endothoracic facia  1320  can abut the inner-most intercostal muscle  1308   c  and separate the intercostal muscles from the parietal pleura  1322 . The pleural cavity  1324  can be disposed between the parital pleura  1322  and the visceral pleura  1326 . The visceral pleura  1326  can abut the lung  1328 . 
       FIG. 14  is an illustration  1400  of an exemplary lead fixation receptacle  1304  illustrated in  FIG. 13 , having features consistent with the present disclosure. 
     Lead receptacle  1304  may comprise a cylindrical body, or lumen  1328 , from an outer side of an outermost intercostal muscle to an inner side of an innermost intercostal muscle of an intercostal space. Lumen  1328  may be configured to support a lead traversing through it. Lumen  1328  may comprise an electrically insulating material configured to inhibit traversal of electrical signals through walls of lumen  1328 . In some variations, end  1336  of the receptacle  1304  may pass through the innermost intercostal muscle  1308   c . In some variations, end  1338  of receptacle  1304  can pass through outermost intercostal muscle  1308   a.    
     Lumen  1328  can terminate adjacent the pleural space  1324 . In some variations, the lumen  1328  can terminate in the mediastinum. In some variations, receptacle  1304  can be configured to be screwed into the intercostal muscles  1308   a ,  1308   b , and  1308   c . Receptacle  1304  can also be configured to be pushed into the intercostal muscles  1308   a ,  1308   b  and  1308   c.    
     Lead receptacle  1304  may include a fixation flange  1330   a . Fixation flange  1330   a  may be disposed on the proximal end of the lumen  1328  and configured to abut the outermost intercostal muscle  1308   a . Lead receptacle  1304  may include a fixation flange  1330   b . Fixation flange  1330   b  can be disposed on the distal end of the lumen  1328  and configured to abut the outermost intercostal muscle  1308   c . Lead receptacle  1304  can be implanted into the intercostal muscles  1308   a ,  1308   b , and  1308   c  by making an incision in the intercostal muscles  1308   a ,  1308   b , and  1308   c , stretching the opening and positioning lead receptacle  1304  into the incision, taking care to ensure that the incision remains smaller than the outer diameter of flanges  1330   a  and  1330   b . In some variations flanges  1330   a  and  1330   b  can be configured to be retractable allowing for removal and replacement of the lead fixation receptacle  1304 . 
     Lead receptacle  1304  can be fixed in place by using just flanges  1330   a  and  1330   b . Lead receptacle  1304  may also be fixed in place by using a plurality of surgical thread eyelets  1332 . Surgical thread eyelets  1332  can be configured to facilitate stitching lead receptacle  1304  to the intercostal muscles  1308   a  and  1308   c  to fix lead receptacle  1304  in place. 
     Receptacle  1304  can include an internal passage  1334 . Internal passage  1334  can be configured to receive one or more leads and facilitate their traversal through the intercostal space  1302 . 
     Lead receptacle  1304  can be formed from an electrically insulating material. The electrically insulating material can electrically isolate the intercostal muscles  1308   a ,  1308   b  and  1308   c  from the leads traversing through lead receptacle  1304 . 
     Lead receptacle  1304  can be formed from materials that are insulative. The material can include certain pharmacological agents. For example, antibiotic agents, immunosuppressive agents to avoid rejection of lead receptacle  1304  after implantation, and the like. In some variations, lead receptacle  1304  can be comprised of an insulative polymer coated or infused with an analgesic. In some variations, the lead receptacle  1304  can be comprised of an insulative polymer coated or infused with an anti-inflammatory agent. The polymer can be coated or infused with other pharmacological agents known to one skilled in the art to treat acute adverse effects from the implantation procedure or chronic adverse effects from the chronic implantation of the lead or receptacle within the thoracic cavity. 
       FIG. 15  is an illustration of lead receptacle  1304  having features consistent with the present disclosure. Lead fixation receptacle can comprise a septum  1340 , or multiple septums disposed traversely within lumen  1338 . Septum  1340  can be selectively permeable such that when a lead is inserted through septum  1340 , septum  1340  can be configured to form a seal around the lead traversing through lumen  1338  to prevent the ingress or egress of gas, fluid, other materials, and the like, through lumen  1338 . Septum  1340  may optionally permit the egress of certain gas and fluid but prevent ingress of such materials through lumen  1338 . 
     In some variations, the lead receptacle can comprise multiple lumens. For example, lead receptacle can comprise a second lumen configured to traverse from an outermost side of an outermost intercostal muscle to an innermost side of an innermost intercostal muscle. Second lumen can be configured to facilitate dispensing of pharmacological agents into the thorax of the patient. 
     The lumens for such a lead receptacle can be used for differing purposes in addition to the passage of a single lead into the pleural space or mediastinum. The multiple lumens can provide access for multiple leads to be passed into the pleural space or mediastinum. 
       FIG. 16  is an illustration of an exemplary lead fixation receptacle  1342  having features consistent with the present disclosure. Lead fixation receptacle  1342  can include a first lumen  1344 , similar to lumen  1338  of the lead receptacle  1304  illustrated in  FIGS. 14 and 15 . Lead fixation receptacle  1342  can include an additional lumen  1346 . Additional lumen  1346  can be provided as a port to provide access to the thoracic cavity of the patient. Access can be provided to facilitate dispensing of pharmacological agents, such as pharmacological agents to treat various adverse effects such as infection or pain in the area surrounding lead receptacle  1342 , pleural space, mediastinum, and/or other areas surrounding the thoracic cavity of the patient. Additional lumen  1346  can provide access for treatment of other diseases or disorders affecting organs or other anatomical elements within the thoracic cavity. For example, additional lumen  1346  can facilitate the evacuation of gas or fluid from the thorax, and the like. 
     The lead receptacle as described with reference to  FIGS. 13-16  can be fixated to cartilage, or bone within the thoracic cavity. In some variations, the lead receptacle can be configured to be disposed between the intercostal muscles and a rib, thereby potentially reducing damage to the intercostal muscles caused by its insertion. The lead receptacle can be in passive contact with tissue surrounding the cardiac notch. For example, the lead receptacle can abut the superficial facia on the outermost side and the endothoracic facia or the parietal pleura on the innermost side. 
     In some variations, the lead receptacle can be actively fixed into position using one end of the lead receptacle. For example, only one flange can include surgical thread holes to facilitate sewing of the flange into the intercostal muscles. 
     Active fixation, whether at flanges, or along the lumen of the lead fixation receptacle, can include, for example, the use of tines, hooks, springs, screws, flared wings, flanges and the like. Screws can be used to screw the lead fixation receptacle into bone or more solid tissues within the thoracic cavity. Hooks, tines, springs, and the like, can be used to fix the lead fixation receptacle into soft tissues within the thoracic cavity. 
     In some variations the lead receptacle can be configured to facilitate in-growth of tissue into the material of which the lead fixation receptacle is comprised. For example, the lead fixation receptacle can be configured such that bone, cartilage, intercostal muscle tissue, or the like, can readily grow into pockets or fissures within the surface of the lead receptacle. Facilitating the growth of tissue into the material of the lead receptacle can facilitate fixation of the receptacle. 
     In some variations, the receptacle can be configured to actively fix between layers of the intercostal muscle. With reference to  FIG. 13 , the layered nature of the intercostal muscle layers  1308   a ,  1308   b  and  1308   c  can be used to facilitate fixation of the lead receptacle into the intercostal space. For example, flanges can be provided that extend between the intercostal muscle layers. Incisions can be made at off-set positions at each layer of intercostal muscle such that when the lead receptacle is inserted through the incisions, the intercostal muscles apply a transverse pressure to the lead receptacle keeping it in place. For example, a first incision can be made in the first intercostal muscle layer  1308   a , a second incision can be made in the second intercostal muscle layer  1308   b , offset from the first incision, and a third incision can be made to the third intercostal muscle layer  1308   c  in-line with the first incision. Inserting the lead receptacle through the incisions, such that the lead receptacle is situated through all three incisions, will cause the second intercostal muscle layer  1308   b  to apply a transverse pressure to the lead receptacle that is countered by the first intercostal muscle layer  1308   a  and the third intercostal muscle layer  1308   c , facilitating keeping the lead receptacle in place. 
     Sensing and detection will be performed using one or more available signals to determine when pacing should be delivered or inhibited. Cardiac signals will be measured from one or more electrodes. Additional non-cardiac sensors may also be used to enhance the accuracy of sensing and detection. Such sensors include, but are not limited to rate response sensors, posture/positional sensors, motion/vibration sensors, myopotential sensors and exogenous noise sensors. One or more algorithms will be utilized to make decisions about pacing delivery and inhibition. Such algorithms will evaluate available signal attributes and relationships, including but not limited to analysis of morphology, timing, signal combinations, signal correlation, template matching or pattern recognition. 
     A pulse generator, such as pulse generator  102  illustrated in  FIG. 1 , can be configured to monitor physiological characteristics and physical movements of the patient. Monitoring can be accomplished through sensors disposed on, or in, the pulse generator, and/or through sensors disposed on one or more leads disposed within the body of the patient. The pulse generator can be configured to monitor physiological characteristics and physical movements of the patient to properly detect heart arrhythmias, dyssynchrony, and the like. 
     Sensor(s) can be configured to detect an activity of the patient. Such activity sensors can be contained within or on the housing of the pulse generator, such as pulse generator  102  illustrated in  FIG. 1 . Activity sensors can comprise one or more accelerometers, gyroscopes, position sensors, and/or other sensors, such as location-based technology, and the like. Sensor information measured by the activity sensors can be cross-checked with activity information measured by any concomitant devices. 
     In some variations, an activity sensor can include an accelerometer. The accelerometer can be configured to detect accelerations in any direction in space. Acceleration information can be used to identify potential noise in signals detected by other sensor(s), such as sensor(s) configured to monitor the physiological characteristics of the patient, and the like, and/or confirm the detection of signals indicating physiological issues, such as arrhythmias or other patient conditions. 
     In some variations, a lead, such as lead  802  in  FIG. 8 , can be configured to include sensors that are purposed solely for monitoring the patient&#39;s activity. Such sensors may not be configured to provide additional assistance during the implantation procedure. These sensors can include pulmonary, respiratory, minute ventilation, accelerometer, hemodynamic, and/or other sensors. Those sensors known in the art that are used to real-time, or periodically monitor a patient&#39;s cardiac activity can be provided in the leads. These sensors are purposed to allow the implanted device to sense, record and in certain instances, communicate the sensed data from these sensors to the patient&#39;s physician. In alternative embodiments, the implanted medical device may alter the programmed therapy regimen of the implanted medical device based upon the activity from the sensors. 
     In some variations, sensors, such as sensors  810  and  812  of  FIG. 8A , may be configured to detect the condition of various organs and/or systems of the patient. Sensor(s)  810 ,  812  can be configured to detect movement of the patient to discount false readings from the various organs and/or systems. Sensor(s)  810 ,  812  can be configured to monitor patient activity. Having a distal end  806  of lead  802  positioned in the cardiac notch abutting the parietal pleura, sensor(s)  810 ,  812  can collect information associated with the organs and/or systems of the patient in that area, for example the lungs, the heart, esophagus, arteries, veins and other organs and/or systems. Sensor(s)  810  can include sensors to detect cardiac ECG, pulmonary function, sensors to detect respiratory function, sensors to determine minute ventilation, hemodynamic sensors and/or other sensors. Sensors can be configured independently to monitor several organs or systems and/or configured to monitor several characteristics of a single organ simultaneously. For example, using a first sensor pair, the implanted cardiac pacing system may be configured to monitor the cardiac ECG signal from the atria, while simultaneously, a second sensor pair is configured to monitor the cardiac ECG signal from the ventricles. 
     A lead disposed in the body of a patient, such as lead  802  of  FIG. 8A , can include sensors at other areas along the lead, for example, sensors  812 . The location of sensors  812  along lead  802  can be chosen based on proximity to organs, systems, and/or other physiological elements of the patient. The location of sensors  812  can be chosen based on proximity to other elements of the implanted cardiac pacing system. 
     Additional leads may be used to facilitate an increase in the sensing capabilities of the implantable medical device. In one embodiment, in addition to at least one lead disposed within the intercostal muscle, pleural space or mediastinum, another lead is positioned subcutaneously and electrically connected to the implantable medical device. The subcutaneously placed lead can be configured to enhance the implantable medical device&#39;s ability to sense and analyze far-field signal&#39;s emitted by the patient&#39;s heart. In particular, the subcutaneous lead enhances the implantable medical device&#39;s ability to distinguish signals from particular chambers of the heart, and therefore, appropriately coordinate the timing of the required pacing therapy delivered by the implantable medical device. 
     Additional leads in communication with the implantable medical device or pulse generator, and/or computing device, can be placed in other areas within the thoracic cavity in order to enhance the sensing activity of the heart, and to better coordinate the timing of the required pacing therapy delivered by the implantable medical device. In certain embodiments, these additional leads are physically attached to the implantable medical device of the present disclosure. 
     The leads used to deliver therapeutic electrical pulses to pace the heart can comprise multiple poles. Each pole of the lead can be configured to deliver therapeutic electrical pulses and/or obtain sensing information. The different leads can be configured to provide different therapies and/or obtain different sensing information. Having multiple sensors at multiple locations can increase the sensitivity and effectiveness of the provided therapy. 
       FIG. 8B  is an illustration  800   b  of an exemplary lead  802  having features consistent with the present disclosure. In some variations, lead  802  can comprise a yoke  816 . The yoke can be configured to maintain a hermetically sealed housing for the internal electrical cables of lead  802 , while facilitating splitting of the internal electrical cables into separate end-leads  818   a ,  818   b ,  818   c . Yoke  816  can be disposed toward distal end of lead  802 . While three end-leads  818   a ,  818   b ,  818   c  are illustrated in  FIG. 8B , the current disclosure contemplates fewer end-leads as well as a greater number of end-leads emanating from yoke  816 . 
     The different end-leads  818   a ,  818   b ,  818   c , can include different electrodes and/or sensors. For example, end-lead  818   b  can include an electrode  808   b  at the distal end  806   b  of end-lead  818   b  that differs from electrode  808   a  at distal end  806   a  of end-lead  818   a . Electrode  808   b  can have flanges  820 . Flanges  820  can be configured to act as an anchor, securing the distal end  806   b  of end-lead  818   b  in position within the patient. Electrode  808   b  with flanges  820  can be suitable for anchoring into high-motion areas of the body where end-lead  818   b  would otherwise move away from the desired location without the anchoring effect provided by flanges  820 . Similarly, electrode  808   c  at the distal end  806   c  of end-lead  818   c  can be configured for a different function compared to the electrodes at the end of other end-leads. 
     Lead  802  can be a multi-pole lead. Each pole can be electronically isolated from the other poles. The lead  802  can include multiple isolated poles, or electrodes, along its length. The individual poles can be selectively activated. The poles may include sensors for monitoring cardiac or other physiological conditions of the patient, or electrodes for deliver therapy to the patient. 
     The sensing characteristics of a patient can change over time, or can change based on a patient&#39;s posture, a multi-pole lead permits the implantable medical device facilitate monitoring a patient&#39;s state through multiple sensing devices, without requiring intervention to reposition a lead. Furthermore, a multi-pole lead can be configured to facilitate supplementary sensing and therapy delivery vectors, such as sensing or stimulating from one pole to a plurality of poles, sensing or stimulating from a plurality of poles to a single pole, or sensing or stimulating between a plurality of poles to a separate plurality of poles. For example, should one particular vector be ineffective at treating a particular arrhythmia, the implantable medical device, or pulse generator, can be configured to switch vectors between the poles on the lead and reattempt therapy delivery using this alternative vector. This vector switching is applicable for sensing. Sensing characteristics can be monitored, and if a sensing vector becomes ineffective at providing adequate sensing signals, the implantable medical device can be configured to switch vectors or use a combination of one or more sensor pairs to create a new sensing signal. 
     In some variations, at yoke  816 , each of the poles of the multi-pole lead can be split into their separate poles. Each of the end-leads emanating from the yoke  816  can be associated with a different pole of the multi-pole lead. 
     Some of the end-leads emanating from yoke  816  can be configured for providing sensor capabilities of and/or therapeutic capabilities to the patient&#39;s heart. Others of the end-leads emanating from yoke  816  can be configured to provide sensor capabilities and/or therapeutic capabilities that are unrelated to the heart. Similarly, the cardiac pacing system herein described can include leads  802 , or medical leads, that provide functionality unrelated to the heart. 
     In some variations, the lead can be bifurcated. A bifurcated lead can comprise two cores within the same lead. In some variations, the different cores of the bifurcated lead can be biased to bend in a predetermined manner and direction upon reaching a cavity. Such a cavity can, for example, be the mediastinum. Bifurcated lead cores can be comprised of shape memory materials, for example, nitinol or other material known in the art to deflect in a predetermined manner upon certain conditions. The conditions under which the bifurcated lead cores will deflect include electrical stimulation, pressure, temperature, or other conditions. In some variations, each core of the bifurcated lead can be configured so that it is steerable by the physician, or an automated system, to facilitate independent advancement of each core of the bifurcated lead, in different directions. 
     In some variations, sensors from the cardiac pacing system may be selected to optimize sensing characteristics of the cardiac signals. Sensing signals, comprised from one or more sensor pairs may be selected via manual operation of the programming system or automatic operation of the implanted cardiac pacing system. Sensing signals may be evaluated using one of several characteristics including signal amplitude, frequency, width, morphology, signal-to-noise ratio, and the like. 
     The cardiac pacing system can be configured to use multiple sensors to generate one or more input signals, optionally apply filtering of varying levels to these signals, perform some form of verification of acceptance upon the signals, use the signals to measure levels of intrinsic physiological activity to, subsequently, make therapy delivery decisions. Methods to perform such activities in part or in total include hardware, software, and/or firmware based signal filters, signal amplitude/width analysis, timing analysis, morphology analysis, morphological template comparison, signal-to-noise analysis, impedance analysis, acoustic wave and pressure analysis, or the like. The described analyses may be configured manually via the programming system or via automatic processes contained with the operation software of the cardiac pacing system. 
     As previously discussed, placing the distal end of the pacing lead in the proper location is important for successful monitoring of a patient&#39;s heart and for efficient delivery of therapy. Furthermore, during placement of the lead, a physician must avoid damaging important blood vessels and other anatomical structures of the patient. The provision of a stable platform from which to deliver the leads can reduce the likelihood of collateral damage to anatomical structures of the patient. However, if a delivery platform is remote from the patient, the patient can move relative to the platform. The present disclosure describes a lead delivery system configured for placement on an anatomical structure of the patient, thereby reducing the risk of altering the relative location between the delivery system and the patient during delivery. When the term lead delivery system is used in the present disclosure, it is contemplated that such may also be capable of delivering components other than leads, for example, the lead delivery system may also be utilized in conjunction with delivery assist components. The lead delivery system may also be referred to as a component delivery system. 
       FIG. 17A  is an illustration  1700  of a side view of an exemplary lead delivery system  1702  for facilitating delivery of a lead, having features consistent with the present disclosure. Lead delivery system  1702  can be provided to facilitate placement of one or more leads into the patient. In some variations, lead delivery system  1702  can be configured to facilitate placement of the lead(s) into and/or through an intercostal space of the patient. For example, lead delivery system  1702  can be configured to facilitate placement of the lead(s) into the intercostal spaces of the patient to the right-hand side of the sternum. Alternatively, lead delivery system  1702  can be configured to facilitate placement of the lead(s) into the intercostal spaces of the patient to the left-hand side of the sternum. Optionally, lead delivery system  1702  can be configured to facilitate placement of the lead(s) into the intercostal space of the patient in the region of the cardiac notch and further through to the mediastinum.  FIG. 17B  is an illustration  1718  of a front view of the exemplary lead delivery system  1702  illustrated in  FIG. 17A .  FIG. 17C  is an illustration  1726  of a top-down view of the exemplary lead delivery system  1702  illustrated in  FIG. 17A . 
     Lead delivery system  1702  can be configured to be affixed to a patient at a desired location such that it remains stationary relative to the patient. Stable fixation to the patient provides an additional benefit where multiple medical instruments are used in concert with lead delivery system  1702 . For example, if a device for assisting in lead delivery is first inserted into delivery system  1702  prior to insertion of the lead itself, the physician will have increased confidence that the system did not move between insertion of the two devices. Optionally, lead delivery system  1702  can be handheld and not affixed to the patient. 
     Lead delivery system  1702  may include base  1712  and lead delivery device  1714 . Base  1712  can be configured to secure lead delivery device  1714  to one or more anatomical structures of the patient. In some variations, lead delivery system  1702  can be secured to an anatomical structure of the patient by use of an adhesive. For example, base  1712  can include an adhesive pad. In some variations, an adhesive pad can be reversibly secured to the patient. Proper placement of the adhesive pad to the patient can be accomplished based upon well-known anatomical landmarks, by imaging equipment, or the like. 
     Lead delivery system  1702  may also be secured to the patient by way of a screw mechanism that securely, but reversibly, affixes lead delivery system  1702  to bone, cartilage or other material within the patient&#39;s body. 
     In some variations, base  1712  of lead delivery system  1702  can include a clamp  1704 . Clamp  1704  can be configured to secure base  1712  to the patient. Clamp  1704  can be configured to secure lead delivery device  1714  to one or more anatomical structures of the patient. Clamp  1704  can include a movable clamp platform  1706  and a stationary platform  1715 . A hook portion  1708  can be disposed at one end of clamp platform  1706 . Hook portion  1708  can be configured to engage with a known anatomical region of the patient. For example, hook portion  1708  can be configured to extend or retract to forcibly engage with the edge of the patient&#39;s sternum, while the opposite edge of the patient&#39;s sternum engages with stationary platform  1715 . At least a portion of clamp platform  1706  may rest on the sternum of the patient. In some variations, the patient&#39;s sternum will be exposed, and clamp  1704  can be secured directly to the sternum. In some variations, clamp platform  1706  can include an adhesive portion configured to be disposed between a clamp platform  1706  and the patient to cause clamp platform  1706  to stick to the patient. 
     In some variations, clamp  1704  can be configured to clamp onto a single rib, multiple ribs, the xyphoid, or other anatomical structures. Clamp  1704  can be engaged around any portion of the chosen anatomical structure. For example, clamp  1704  can be configured to clamp on to the sides of an anatomical structure. In some variations, clamp  1704  can be configured to clamp on the top and bottom of an anatomical structure. In some variations, clamp  1704  can be configured to engage outwardly to secure lead delivery system  1702  between two anatomical structures. When secured to two anatomical structures, lead delivery system  1702  can be secured by expansion forces exerted by clamp  1704  outwardly from clamp platform  1706 , against the two anatomical structures. For example, clamp  1704  can be configured to facilitate exerting an outward pressure against two ribs of the patient. The resultant force exerted back against clamp  1704  can keep clamp  1704  in place, relative to the patient. 
     Clamp  1704  can be tightened when clamp  1704  has been positioned on, around, and/or between the intended anatomical structure(s). In some variations, a screw, an adjustable latch, a ratcheting mechanism, or the like, can be used to adjust clamp  1704 . The pressure of clamping clamp  1704  on the anatomical structure may be adjusted with an adjustment handle  1720 . Adjustment handle  1720  can also be configured to make adjustments, or refinements, to the location of lead delivery system  1702  as it may become necessary to fine tune the position of lead delivery system  1702  after it has been secured to an anatomical structure of the patient. 
     As previously noted, it is important to avoid certain critical structures and vessels during lead delivery, such as the heart, lungs, pericardium, internal thoracic artery, and other major vessels of the anterior thoracic region. Exemplary lead delivery system  1702 , depicted in  FIG. 17 , can facilitate the avoidance of critical structures through its locating the lead insertion point proximate the lateral margin of the sternum, especially when system  1702  is clamped to a patient&#39;s sternum (utilizing, for example, stationary platform  1715  and retractable hook  1708 , as discussed further below). In this implementation, distal end  1713  of cannula  1716  is located proximate stationary platform  1715  and will result in a lead insertion location proximate the lateral margin of the sternum. 
     Lead delivery devices and systems of the present disclosure are not required to have a clamp  1704 , as depicted in  FIG. 17 , or to necessarily be a fixed to the patient in any way. For example, lead delivery devices and systems similar to those previously described and depicted in  FIG. 12  and  FIG. 17  (without clamp  1704 ) may be used without fixation to the patient. Such systems have been described, for example, as facilitating the insertion of lead(s) to the side of the sternum and in the region of the cardiac notch. In one implementation, lead delivery systems  1702  can effect such placement by way of a physician (or other trained healthcare provider) palpating the lateral margin of the sternum, at an intercostal space, prior to making an incision or other method for point of entry (e.g., puncture). Alternatively, lead delivery systems  1702  may be configured to allow for a distal end of the system to be pressed against the sternum of a patient and slid until reaching the lateral margin, then dropping through the intercostal muscles to create a path for lead(s). For example, in one implementation, following the physician identifying an insertion point above a patient&#39;s sternum, stationary platform  1715  may be inserted through the incision down to the sternum. The physician may then slide the distal tip of stationary platform  1715  across and against the sternum of the patient until reaching the lateral margin, wherein the pressure applied to the lead delivery device  1714  causes stationary platform  1715  to rest against the sternum, and the distal tip of stationary platform  1715  to insert through the intercostal muscles at the lateral margin of the sternum. The bottoming out of stationary platform  1715  against the sternum prevents over insertion of lead delivery system  1702 , and specifically the distal tip of stationary platform  1715 . Once positioned, distal end  1713  of cannula  1716  can be inserted to deploy lead(s) as described herein. 
     In one implementation, such a distal end may be configured to puncture the tissue, for example with a relatively blunt access tip, to facilitate entry into the intercostal space without requiring a surgical incision to penetrate through the intercostal muscles. A blunt access tip, while providing the ability to puncture and push through tissue, does not cut, thereby reducing the potential for damage to the pericardium or other internal organs the tip may contact should such contact occur. 
     Lead delivery systems configured for lead insertion proximate the lateral margin of the sternum may optionally be designed to effect lead placement to a substernal location. For example, a distal end of the lead delivery system may be shaped or curved, or may be articulable to move after passing the sternum. Alternatively, the lead itself may be articulable in a similar manner. 
     When lead delivery systems  1702  are configured to be pressed against the sternum of the patient, slid across the sternum until reaching the lateral margin, and then dropped down through the intercostal tissue immediately lateral to the sternal margin, this process may be utilized after a physician has made an incision above the sternum. Such an incision may have been made, for example, to insert a pulse generator, as previously described. In such cases, the lead delivery system may easily traverse the sternum prior to puncturing the intercostal muscles and creating a path to the mediastinum for insertion of lead(s). Proper lead delivery system and lead insertion depth determinations in such cases are facilitated by the fact that sternum and rib cage thicknesses are similar across patient populations. As such, the insertion depth of the lead delivery system may be set at a nominal sternum thickness or slightly less, and thereafter be adjusted deeper to ensure that the lead delivery system does not extend too far within the mediastinum. However, in some cases, lead delivery systems may be utilized in a percutaneous manner, without an incision above the sternum (or without an incision at other entry locations described herein). In these cases, the thickness of a patient&#39;s subcutaneous tissue must be accounted for. 
     Numerous methods for proper lead depth determination have been described herein including systems, methods and software for automating the lead delivery process. These and other implementations may be modified to further account for subcutaneous tissue thickness estimations. In one example, an implanting physician may assess the thickness of subcutaneous tissue based upon specific patient attributes such as height, weight, sex, waist size, chest size, sternum length, etc. These patient attributes may be assessed individually or in combination to predict subcutaneous tissue thickness. Alternatively, direct measurement of the subcutaneous tissue thickness may be made by means such as a needle probe, ultrasound, CT scan, MRI, or the like. Information related to items such as the distance between the posterior surface of the sternum and the pericardium, the distance between the sternal margin to the thoracic vein or artery, and sternum thickness may then be used by the physician, or by an automated delivery system, to adjust the intended lead implantation location, orientation and depth. 
     With further reference to  FIG. 17 , exemplary lead delivery system  1702  can include a lead delivery device  1714  configured to facilitate delivery of a lead into the patient to a desired location. Lead delivery device  1714  can include a lead advancer, which can be configured to incrementally advance a lead into a patient. The lead may be advanced into a patient by a predefined amount. The lead advancer can be configured to facilitate the delivery of leads to the correct position, orientation and depth within the patient. 
     Leads delivered by lead delivery system  1702  may be leads configured to deliver therapeutic electrical pacing to the heart of the patient. Leads delivered by lead delivery system  1702  can also be leads configured to obtain physiological information about the patient, such as heart function, lung function, the performance of various blood vessels, and the like. 
     Lead delivery device  1714  can be configured to advance a lead through an intercostal space of the patient and, optionally, into the mediastinum of the patient. Lead delivery device  1714  can be configured to position the distal end of the lead at any of the positions described in the present disclosure. Lead delivery device  1714  can also be configured to control an angle at which a lead is inserted into the patient. 
     Lead delivery system  1702  can include a cannula  1716 , which may extend through the length of lead delivery device  1714 . Cannula  1716  can also extend through the lead advancer. Cannula  1716  can be configured to receive a lead for insertion and may be configured to accompany a lead as it is inserted into the patient. In some variations, cannula  1716  can be configured to receive delivery assist components (discussed below) for insertion into the patient. In some variations, lead delivery system  1702  can include multiple cannulas for simultaneous delivery of leads and/or delivery assist components into the patient. 
     In some variations, a screw, an adjustable latch, a ratcheting mechanism, or the like, can be used to adjust the distance between the distal end  1713  of cannula  1716  and stationary platform  1715 . Such adjustments or refinements may become necessary to fine tune the position of lead delivery system  1702  and the location of the distal end  1713  of cannula  1716  after it has been secured to an anatomical structure of the patient 
     In some instances, a smaller cannula opening may ease the insertion through tissue. As such, in additional variations, the size of the cannula opening may be variably controlled by the operator. The cannula may, for example, be comprised of two cannula halves, or multiple cannula segments, that expand or separate to a desired opening size. The variably selected cannula opening size may be controlled via screw, an adjustable latch, a ratcheting mechanism, lever, or the like, in order to facilitate delivery of a variety of lead shapes and sizes. 
     Lead delivery system  1702  may utilize delivery assist component(s) such as a needle, a guide wire, guide catheter, sheath, expandable catheter, balloon catheter and the like. A delivery assist component can be configured to facilitate delivery of a lead into the patient. Delivery assist components may be configured to be inserted into a patient and advanced to the desired location prior to lead insertion. Alternatively, a delivery assist component can be configured to be inserted into the patient with a lead and advanced with the lead to the desired location. The delivery assist component can be used to create space and minimize damage to surrounding tissue prior to, or in connection with, the deployment of a lead into the patient. The delivery assist component can be removed from the patient once the lead has been placed at the desired location. Delivery assist components can be inserted into the patient by the lead delivery system  1702  in much the same way as a lead. Delivery assist components may incorporate sensors. Such sensors can include the sensor types described in the present disclosure for use on leads to monitor the location of leads with respect to patient anatomy. It is understood that delivery assist components may interact with lead delivery system  1702  in much the same way as leads themselves, as described herein. 
     Careful advancement of the component into the patient is desirable. Lead delivery system  1702  can include a lead advancer, which can be configured to incrementally advance a lead into a patient in response to an interaction by an operator. Limiting movement of the lead advancing into the body can avoid accidental perforation and damage to anatomical structures. In some variations, lead delivery system  1702  can include a trigger  1724 , which can be configured to activate a ratcheting mechanism to advance the lead. One pull on trigger  1724  connected to the ratcheting mechanism can cause the lead to be advanced a known, prescribed, amount. For example, the amount can be set to 1 mm, 2 mm, or the like. In some variations, this length can be set or programmed by the physician. In some variations, a partial pull on trigger  1724  can result in a partial advancement of the lead by a partial amount of the set amount. For example, where depressing the trigger fully can result in an advancement of 1 mm and therefore a partial depression of the trigger can be set to cause the result of an advancement of 0.5 mm. The lead delivery system  1702  can include a limit on the number of trigger  1724  pulls permitted within an interval. For example, the lead delivery system  1702  may restrict the physician from pulling trigger  1724  more than one time per second. In another option, the lead delivery system  1702  may require the physician to actively set a trigger limit in order to permit trigger  1724  pulls in excess of the permitted interval. 
     Lead delivery system  1702  can include a locking mechanism activated by a locking switch  1728  that can reversibly lock a lead with respect to the lead delivery system  1702 . When locked, the lead being delivered to the patient can be engaged with delivery system  1702  such that it cannot be moved independent of movement from, say, the ratcheting system. When unlocked, the lead can move freely within cannula  1716  of lead delivery system  1702 . Lead delivery system  1702  can be further configured to only permit movement of the lead in one direction when locking switch  1728  is in the unlocked position. 
     Where a delivery assist component is used and unlocked from lead delivery system  1702 , the physician can remove the delivery assist component, such as a needle, from cannula  1716 . The physician may then insert another delivery assist component, or a lead, into cannula  1716  of lead delivery system  1702 . The physician can lock the lead, or the new delivery assist component, for example, into the ratcheting mechanism of lead delivery system  1702 . The physician, or an automated system, can then advance the lead within the patient to a depth indicated by the previous component&#39;s readout. In some variations, the physician can use the previous depth readout with sensors or physical markers on the lead to ensure proper placement of the lead. 
     While the lead is being inserted into the patient to the desired location, the movement of the lead can be metered. Transverse movement of the lead can be metered as well the depth of the lead into the patient. Metering the movement of the lead can avoid excessive movement of the lead. In some variations, movement can be metered by a ratcheting mechanism and the magnitude of the movement of the lead can be presented to the operator. For example, a reading indicating the amount of movement can be presented to the operator, such as through reading window  1722 . 
     In some variations, lead delivery system  1702  can be configured to coordinate with real-time imaging equipment to assess the relative location of the lead being delivered by lead delivery system  1702 . 
     Sensor(s) associated with lead delivery system  1702  can facilitate delivery. Sensor(s) can be disposed on the lead delivery device  1714 , remote from the lead delivery device  1714 , such as on a gurney, or in an operating room, on the lead itself, or in other locations. 
     Sensor(s) may be utilized to help determine an appropriate insertion point for the lead by, for example, identifying blood-filled vessels such as arteries and veins below the surface of the skin. An example of such identification of subcutaneous vessels is described in relation to  FIGS. 9A and 9B . Similarly, sensors can be used to identify the location of ribs, or other anatomy. The use of sensors of the types identified herein facilitate determination of an appropriate insertion point that will avoid damage to critical anatomy. 
     Sensor(s) can also utilized to determine a proper depth in the patient for the distal end of the lead, or proper positioning with respect to specific anatomy. As previously described, different tissues within the patient&#39;s body can demonstrate varying characteristics. The differing physiological characteristics of the tissues of the body can facilitate placement of the delivery system and/or lead at the desired location. Lead delivery system  1702  can be configured to monitor the physiological characteristics of the tissues surrounding the distal end, or advancing end, of the lead and/or delivery assist component being delivered to the desired position. Physiological sensors, such as pressure sensors, impedance sensors, accelerometers, pH sensors, temperature sensors, and the like, can monitor the characteristics of the anatomy at the end of the implanted, or advancing, lead or device. Lead delivery system  1702  can be configured to determine the location of the lead being implanted based on the detected physiological characteristics as has been described with reference to  FIGS. 10-13  and at other locations within the present disclosure. 
     Lead delivery system  1702  can be configured to provide real-time feedback to an implanting physician based on readings from the above-mentioned sensors. Feedback can be provided with indicators, alarms or the like. 
     Lead delivery system  1702  can be automated. Automating the lead delivery system can allow a physician to set up the system and then rely on sensors and computer control of lead delivery system  1702  to deliver the lead to the desired location. In some variations, the lead delivery system  1702  can be semi-automatic, where measurements and advancements made by lead delivery system  1702  occur automatically, but only after the physician reviews certain measurements or replies to prompts provided by lead delivery system  1702 .  FIG. 18  is an illustration of a schematic diagram  1800  showing components of lead delivery system  1702  having features consistent with the current subject matter. Lead delivery system  1702  can include, or be associated with, a computing device  1802  that can be configured to control the operation of delivery system  1702 . Computing device  1802  can include processor(s)  1804  configured to cause computing device  1802  to transmit signals to the various elements of the lead delivery system  1702  and/or other devices to control lead delivery system  1702 . Computing device  1802  can also be configured to control other devices in concert with lead delivery system  1702 . 
     Computing device  1802  can include electronic storage  1806  to store computer-readable instructions for execution by processor(s)  1804 . The computer-readable instructions can cause processor(s)  1804  to perform functions consistent with the present disclosure. The functions that can be performed include the functions described herein attributable to a physician. 
     Sensors disposed on an advancing lead, a delivery assist component, or the lead delivery system  1702  (all referred to as component sensors  1808  in  FIG. 18 ), can be used to facilitate the identification of an insertion point, and the delivery of a lead, as discussed herein. External sensor machinery  1810  such as x-ray machines, fluoroscopy machines, ultrasound machines, and the like, can also be used to assist in the lead delivery process. 
     Computing device  1802  can be in communication with one or more component sensors  1808  and/or external sensors  1810 . Computing device  1802  may communicate with such sensors through wired or wireless communication systems. As described throughout the present disclosure, such sensors can be used by computing device  1802  to determine an insertion point that is optimally placed with respect to anatomy such as the sternum, ribs, or critical arteries. The sensors can also be used by computing device  1802  to determine a safe path of advancement and fixation for a lead, which will avoid damage to critical structures and provide optimal distal end placement for effective pacing and sensing. Optimal placement effected by an automated delivery system  1702 , in conjunction with computing device  1802  can result in the distal end of a lead being placed in any of the locations described within the present disclosure (for example, intercostally into the mediastinum, or to just beyond the innermost intercostal muscle, etc.). 
     Computing device  1802  can be further configured to control one or more actuators  1814  disposed on a lead delivery system  1702 . The lead delivery system can comprise motors configured to advance or retract a delivery assist component and/or lead, or to effect lateral movements, or to change the angle of advancement or retraction of the lead. 
     Computing device  1802  and automated lead delivery system can be further configured to present information via indicators, alarms or on a screen associated with the placement of a lead and/or delivery assist component. Computing device  1802  can be in electronic communication with a display  1812 . Computing device  1812  can be configured to cause a presentation on display  1812  of information associated with the advancing lead. For example, measurements obtained by sensor(s)  1808  and/or  1810  can be processed by processor(s)  1804  to provide images or representations of anatomy in the vicinity of an advancing lead. Computing device  1802  can be configured to cause presentation of warnings on display  1812 . For example, computing device  1802  can be configured to cause an indication to be presented on display  1812  that the end of the lead has reached the desired location within the patient. Display  1812  can display an indication of damage to tissues caused by an advancing lead. Display  1812  can display an indication of future potential damage of tissues allowing the operator to stop the procedure or determine solutions to circumvent problems. In some variations, processor(s)  1804  can be configured to determine solutions to circumvent problems and cause the solutions to be presented on the display  1812 . 
     While components have been described herein in their individual capacities, it will be readily appreciated the functionality of individually described components can be attributed to one or more other components or can be split into separate components. This disclosure is not intended to be limiting to the exact variations described herein, but is intended to encompass all implementations of the presently described subject matter. 
     In the descriptions above, phrases such as “at least one of” or “one or more of” may occur followed by a conjunctive list of elements or features. The term “and/or” may also occur in a list of two or more elements or features. Unless otherwise implicitly or explicitly contradicted by the context in which it used, such a phrase is intended to mean any of the listed elements or features individually or any of the recited elements or features in combination with any of the other recited elements or features. For example, the phrases “at least one of A and B;” “one or more of A and B;” and “A and/or B” are each intended to mean “A alone, B alone, or A and B together.” A similar interpretation is also intended for lists including three or more items. For example, the phrases “at least one of A, B, and C;” “one or more of A, B, and C;” and “A, B, and/or C” are each intended to mean “A alone, B alone, C alone, A and B together, A and C together, B and C together, or A and B and C together.” Use of the term “based on,” above is intended to mean, “based at least in part on,” such that an unrecited feature or element is also permissible. 
     The subject matter described herein can be embodied in systems, apparatus, methods, and/or articles depending on the desired configuration. The implementations set forth in the foregoing description do not represent all implementations consistent with the subject matter described herein. Instead, they are merely some examples consistent with aspects related to the described subject matter. Although a few variations have been described in detail above, other modifications or additions are possible. In particular, further features and/or variations can be provided in addition to those set forth herein. For example, the implementations described above can be directed to various combinations and subcombinations of the disclosed features and/or combinations and subcombinations of several further features disclosed above. In addition, the logic flows depicted in the accompanying figures and/or described herein do not necessarily require the particular order shown, or sequential order, to achieve desirable results.