Patent Publication Number: US-11642518-B1

Title: Temporary pacing lead

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This patent application claims priority to U.S. patent application Ser. No. 15/642,084, entitled “Temporary Pacing Lead,” filed Jul. 5, 2017, and U.S. Provisional Application Ser. No. 62/493,490, entitled “Temporary Coiled Pacing Lead,” filed 5 Jul. 2016, U.S. Provisional Application Ser. No. 62/495,765 entitled “Temporary Coiled Over the Wire Pacing Lead,” filed 23 Sep. 2016, and U.S. Provisional Application Ser. No. 62/602,397, entitled “Temporary Coiled Floppy Distal Pacing Lead,” filed 21 Apr. 2017, all of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Temporary pacing is performed in patients having cardiac arrhythmias as a bridge to permanent pacing or to recovery; temporary pacing also provides prophylactic utility for specific medical procedures including, for example, transcatheter aortic valve replacement (TAVR) procedures. Such arrhythmias can manifest as bradycardia or tachycardia and can result in hemodynamic instability to the patient. Often bradycardia can occur as a result of sinus node dysfunction or atrioventricular block. Acute therapy can be obtained via placement of a temporary lead in the right ventricle (RV); the temporary pacing lead receives an electrically generated signal from an external pulse generator located external to the patient. 
     Current temporary pacing leads are generally placed via a percutaneous transvenous access, via a direct epicardial placement of the electrode via a surgical access site or transcutaneous using patches placed on the body surface, i.e., skin. The pacemaker lead can be a unipolar lead with the negative or cathode electrode located at or near its distal end; alternately, the lead can be a bipolar lead thereby containing both the negative cathode and the positive anode on the lead body separated by a small distance of a few millimeters. The unipolar lead requires that a separate anode be located adjacent the subcutaneous tissue at a remote location located several inches away from the cathode. The unipolar lead provides for a greater ease of capture of the electrical pulse by the myocardium from the pacemaker generator and hence is often used for temporary pacing. The bipolar lead provides a benefit over the unipolar lead for requiring a lower threshold energy to obtain capture and hence has greater application for permanent pacing with a preserved battery life for the implanted pulse generator. 
     Temporary pacing leads can have active fixation elements such as a distally located screw-shaped electrode that is screwed into the myocardium. Such active fixation can hold the lead in place but is also more difficult to place during implantation and more difficult to remove after a few days. Active fixation leads carry a greater likelihood of myocardial perforation and potential for tamponade. Temporary leads can also have passive fixation such as tines that are designed to be entangled within the trabeculae of the endocardial surface to provide adequate lodging and also can be time-consuming to place. Other temporary leads are more easily and quickly placed without active or passive fixation elements but still require fluoroscopy and are easily dislodged by small movements of the pacing lead in relation to the patient thereby resulting in loss of capture of the electrical stimulus from the pacemaker generator even due to small micro-dislodgements. Temporary pacing leads can also have flow-directed balloons located near the distal end to assist with advancement of the pacing lead in the RV chamber but difficult to adequately position for capture and thus require a significant amount of manipulation under fluoroscopy for optimal positioning; flow-directed balloons are less reliable for providing a preferred location for the pacing lead. 
     Current temporary pacing leads often have a general linear configuration near the distal region of the lead. A slight curve can be formed into the lead to allow it to lay against the wall of a heart chamber such as the right ventricle (RV). Due to the linear configuration, the distal end of the temporary lead can be traumatic to the heart wall and can protrude, penetrate, or perforate through the wall of the heart leading to potential tamponade and which can lead to death of the patient. Placement of such linearly configured leads is performed under fluoroscopic guidance in order to position the lead properly against the endocardial surface of the heart and to prevent inadvertent perforation of the heart wall. 
     Due to the general linear configuration of standard temporary leads, the distal region of the lead does not easily maintain a position adjacent to the endocardial surface which is needed to maintain sustained electrical capture of the myocardial tissue. Instead the distal region of the lead can easily dislodge and lose capture shortly following placement. The proximal shaft of such a linearly-configured temporary lead is often secured with sutures and adhesive dressing near its manifold to the patient&#39;s tissue near the access site to help prevent dislodgement of the lead and loss of capture, however patient movement and inherent motion of the heart tend to easily result in dislodgement of the lead and resultant loss of capture. If the temporary pacing lead should need to be repositioned due to lack of capture as a result of dislodgement, care must be taken and once again requires the use of fluoroscopy, to ensure that the pacing lead does not perforate the myocardial tissue during repositioning. This often requires patient transfer back to the cardiac catheterization laboratory. 
     Vascular access is obtained via a percutaneous transvenous site through which the temporary pacing lead is performed under fluoroscopic guidance. The lead can be provided percutaneous access using the femoral vein (FV), subclavian vein (SCV), the internal jugular vein (UV), or other suitable venous access sites. The lead is then advanced through the right atrium (RA) and into the RV. The bipolar lead has a negative electrode or cathode and adjacent positive electrode or anode which are found on the distal segment of the lead positioned to obtain adequate contact with the myocardium of the RV such that the electrical pulse from the pulse generator is transmitted to and captured by the myocardium. Radiation exposure while using fluoroscopy can be detrimental to a patient. 
     Several complications exist during the placement and operation of temporary pacemaker leads; such complications include myocardial damage, generation of arrhythmias, perforations of the myocardium, tamponade, trauma to the tricuspid valve, and dislocation or dislodgement of the pacing lead with loss of capture. Many of the pacer leads are traumatic and their distal end, wherein the electrodes are located, can penetrate the myocardial tissue or perforate the atrial or ventricular wall of the heart. 
     What is needed is a temporary pacing lead that is easily placed and is atraumatic to the myocardial tissues of the heart including the tissues of the RA and RV. The lead should be placed without the need for fluoroscopy and its associated inconvenience, time, and radiation, also preferably without the need for echocardiographic guidance. The lead should be configured such that more than one cathode and anode is positioned on the lead such that positioning of the lead does not require precise visualization as required by current standard leads which are placed using fluoroscopy. The lead should not be easily dislodged once it is placed in the RV; the lead should be easily stabilized or held in a stationary position in relation to the access sheath such that dislodgements and loss of capture is reduced. If the lead is displaced, it should be easily repositioned without the need for fluoroscopy or ventricular capture preserved with the use of other electrode pairs in a bipolar configuration or using a monopolar option. The temporary pacing lead should be easily removed following the return of a stable patient rhythm or placement of a permanent pacemaker. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a temporary pacing lead that overcomes the objections found in current standard temporary pacing leads. The pacing lead can be used in any of the four chambers of the heart. Often however, the pacing lead is placed into the right ventricle (RV) and hence the discussion presented will focus on this chamber of the heart. 
     The present invention is specifically directed to a pacing lead for temporary atraumatic placement on a wall surface of a chamber of an animal body part, which can be the endocardial surface of a cardiac chamber, to deliver an electrical signal comprising a lead manifold located outside the animal body; and a pacing lead body connected to the lead manifold, the pacing lead body having a proximal end and a distal end, wherein the pacing lead body comprises a curled shaft having a distal and a proximal end which can be achieved in one embodiment with catheter-shaped memory and a shaped curved memory, wherein the curled shaft is located in the distal end of the pacing lead body for placement of the lead body against the surface of the body part. The curled shaft further includes a plurality of cathode sites, which cathode sites are connected via electrical continuity such that at least one of the plurality of the cathode sites is adapted to be temporarily connected to the wall surface. 
     The present invention is further directed to a pacing lead for temporary atraumatic placement on a wall surface of a chamber of an animal body part, which can be the endocardial surface of a cardiac chamber, to deliver an electrical signal comprising a lead manifold located outside the body; a pacing lead body connected to the lead manifold, the pacing lead body having a proximal end and a distal end, wherein the pacing lead body comprises: a curled shaft having a distal end and a proximal end, which can be achieved in one embodiment with catheter-shaped memory and an outward memory force, wherein the curled shaft is located in the distal end of the pacing lead body for placement of the lead body against the surface of the body part, the curled shaft further including a plurality of cathode sites, which cathode sites are connected via electrical continuity such that at least one of the plurality of the cathode sites is adapted to be temporarily connected to the wall surface, wherein the cathode sites are connected to a cathode connecting wire extending along the pacing lead body to a cathode connector on the lead manifold, wherein the cathode connector is connected via the cathode connecting wire to a negative pole of a pulse generator, wherein the pulse generator provides voltage and current to the plurality of cathode sites, and an internal lumen having a proximal end and a distal end for receiving a placement stylet; and an introducer sheath to assist in the placement of the pacing lead within the chamber, wherein the introducer sheath comprises an inner surface and an outer surface, wherein the pacing lead is adapted to extend distally through the introducer sheath, wherein the introducer sheath includes an anode site positioned of the outer surface of the introducer sheath, and wherein the anode site is electrically coupled to a temporary pulse generator. 
     The present invention is further directed to a pacing lead for temporary atraumatic placement on a wall surface of a chamber of an animal body part to deliver an electrical signal. The pacing lead comprises a lead manifold located outside the animal body; a pacing lead body connected to the lead manifold, the pacing lead body having a proximal end and a distal end. The pacing lead body comprises a curled shaft having a distal end and a proximal end, a shaped curved memory and an outward memory force, wherein the curled shaft is located in the distal end of the pacing lead body for placement of the lead body against the surface of the body part, the curled shaft further including a plurality of cathode sites, which cathode sites are connected via electrical continuity such that at least one of the plurality of the cathode sites is adapted to be temporarily connected to the wall surface, wherein the cathode sites are connected to a cathode connecting wire extending along the pacing lead body to a cathode connector on the lead manifold, wherein the cathode connector is connected via the cathode connecting wire to a negative pole of a pulse generator, wherein the pulse generator provides voltage and current to the plurality of cathode sites, and an internal lumen having a proximal end and a distal end for receiving a placement stylet. The pacing lead further comprises an introducer sheath to assist in the placement of the pacing lead within the chamber, wherein the introducer sheath comprises an inner surface and an outer surface, wherein the pacing lead is adapted to extend distally through the introducer sheath, wherein the introducer sheath includes an anode site positioned of the outer surface of the introducer sheath, and wherein the anode site is electrically coupled to a temporary pulse generator; and a control fiber connected to the lead body distal end, wherein the control fiber traverses external to the lead body distal region, wherein the lead body includes a control fiber opening at the proximal of the curled shaft, wherein the control fiber extends through the control opening into a control fiber lumen within the lead body to the lead manifold at the proximal end of the lead body, wherein the lead manifold includes a holding-tensioning member for securing the control fiber and providing tension to the control fiber. 
     The present invention is further directed to method of temporarily and atraumatically placing a pacing lead on a wall surface of a chamber of an animal body part, wherein the pacing lead comprises a lead manifold located outside the animal body, and a pacing lead body connected to the lead manifold, the pacing lead body having a proximal end and a distal end. The pacing lead body comprises a curled shaft having a distal end and a proximal end and a shaped curved memory, wherein the curled shaft is located in the distal end of the pacing lead body for placement of the lead body against the surface of the body part, the curled shaft further including a plurality of cathode sites, which cathode sites are connected via electrical continuity such that at least one of the plurality of the cathode sites is adapted to be temporarily connected to the wall surface, and an internal lumen having a proximal end and a distal end for receiving a placement stylet. The method comprises the following steps: (a) slidingly advancing the stylet within the internal lumen toward the distal end of the lead body of the pacing lead to cause the lead distal region to form a generally linear shape; (b) advancing the pacing lead through the introducer sheath toward the chamber of the animal body part; (c) holding the stylet in a fixed position and advancing the pacing lead distally into the chamber; (d) slidingly removing the stylet from the distal end of the lead body of the pacing lead, such that the distal end initiates the formation of the curled shaft within the chamber; and (e) advancing the temporary pacing lead further while maintaining the stylet at a fixed position to allow the lead distal end to form an equilibrium configuration of a curved loop. 
     The present invention is further directed to a method of temporarily and atraumatically placing a pacing lead on a wall surface of a chamber within an animal body part, wherein the pacing lead comprises a lead manifold located outside the animal body part, and a pacing lead body connected to the lead manifold, the pacing lead body having a proximal end and a distal end. The pacing lead body comprises: a curled shaft having a distal end and a proximal end and a shaped curved memory, wherein the curled shaft is located in the distal end of the pacing lead body for placement of the lead body against the surface of the body part, the curled shaft further including a plurality of cathode sites, which cathode sites are connected via electrical continuity such that at least one of the plurality of the cathode sites is adapted to be temporarily connected to the wall surface, an internal lumen having a proximal end and a distal end for receiving a placement stylet, and a control fiber connected to the distal end of the pacing lead body, wherein the control fiber traverses external to the pacing lead body distal region, wherein the lead body includes a control fiber opening at the proximal end of the curled shaft, wherein the control fiber extends through the control opening into a control fiber lumen within the pacing lead body to the lead manifold at the proximal end of the pacing lead body, wherein the lead manifold includes a holding-tensioning member for securing the control fiber and providing tension to the control fiber. The method comprises the following steps: (a) placing the pacing lead body in a linear configuration to traverse an introducer sheath; (b) introducing a stylet into the internal lumen; (c) providing sufficient tension to the control fiber from the lead body distal end to the control opening to provide a lead loop controlled radius of curvature to the lead distal region of the curled shaft; (d) traversing the lead body distal end of the lead body to the chamber; (e) applying tension to the control fiber via the holding-tensioning member thereby causing the lead body distal region to form a closed loop having a lead loop controlled radius of curvature sufficient to allow entry of the distal end of the pacing lead body into the chamber in an atraumatic manner; and (f) releasing the tension of the control fiber to enable the lead distal region to form the curled shaft having an open loop. 
     The curled shaft of the present invention contains at least one and preferably a plurality of cathode sites all of which are connected together via electrical continuity to form a single cathode or cathode electrode which characterizes the present temporary pacer lead as a unipolar lead. The plurality of cathodes sites allows the present unipolar temporary pacing lead to be easily placed within the chamber of the heart such that at least one of the cathodes sites is in contact with a region of the endocardium to create a capture site that is needed to temporarily pace the heart. The curled shaft applies a small outward force onto two opposing walls of the heart chamber and hence place the cathode sites into contact with the endocardial surface of the myocardium to ensure electrical contact and capture of the pacing signal from the pulse generator. 
     Due to this multiplicity of cathode sites and combined with the atraumatic shape of the distal curled region, the pacer lead of the present invention can be placed without fluoroscopic imaging or possibly under echo guidance without the concern for perforation of the heart wall while ensuring that at least one of the cathode sites is creating an electrical capture of the myocardium for temporary pacing. Placement of the pacing lead will not require the fluoroscopic guidance since the curled distal region with the multiplicity of cathode sites does not require the visualization provided by fluoroscopy as required by standard leads to reduce the likelihood for pacing lead perforations and ensure precise placement for standard temporary pacing leads. Confirmation of proper placement of the curled distal region into the RV can be guided by echo. 
     This temporary pacing lead embodiment of the present invention has a unipolar cathode electrode rather than a bipolar electrodes placed on the lead body. The unipolar cathode allows the present invention to provide capture of the electrical pulse signal by the myocardium easier than a bipolar electrode due to the ability to provide a larger current density required to reach a capture threshold. For temporary pacing, the ease of myocardial capture is of greater importance than the lower capture threshold found in bipolar leads and needed to conserve battery power for a permanent pacemaker. The ease of capture combined with the ability to capture with any of the multiplicity of cathode sites provides the multiple unipolar cathode sites of the present invention with an advantage over other pacing leads to provide an even greater ease and consistency of capture. 
     Placement of the temporary pacing lead of the present invention may be performed by first placing a placement stylet or guidewire into an internal lumen of the pacing lead. The stylet, for example, may have a linear or curved shape that does not form a closed loop; the stylet has a radius of curvature that may be much larger than the radius of curvature of the closed loop of coiled shaft of the temporary pacing lead of some embodiments of the present invention. Placement of the stylet into the lumen of the pacing lead causes the distal coiled shaft of the pacing lead to form a more gently curved shape that allows the pacing lead to traverse the venous vasculature to the heart and cross the tricuspid valve (TCV) annulus. The distal end of the pacing lead can be a closed end such that the stylet is able to extend within the internal lumen of the pacing lead but cannot extend distally beyond the closed distal end. Once the pacing lead is across the TCV, the pacing lead can be advanced into the heart chamber where the distal region of the pacing lead can form a distal curled region within the RV. The pacing lead can be advanced under echo guidance to place the distal curled region into contact with the lateral wall, apex, and septal wall of the RV. The distal curled region has a radius of curvature that is similar to the endocardial surface of the chamber of the heart and hence it confers an atraumatic character. 
     In another embodiment the pacing lead can have an open distal end such that the pacing lead can pass over a floppy coiled guidewire that has been placed through the vasculature and into the right ventricle. This atraumatic guidewire would have a softer curved shape located within the chamber of the right ventricle and a stiffer and straighter shaft located within the right atrium and venous vasculature extending from the access site to the heart. The pacing lead of this embodiment can then be advanced over the wire into the right ventricle and around the coiled wire positioned in the right ventricle in a safe and atraumatic manner. 
     To assist in placing the lead into the RV under hemodynamic guidance, a distal orifice or orifices can be placed in the distal region of the coiled shaft at a location distal to the cathode sites. The orifices connect to a fluid-filled lumen enabling delay of pressure waveform when connected to a pressure transducer characteristics of the chamber in which it rests. Again, observation of the pressure signal within the blood vessel or chamber via a pressure transducer that is sealingly connected to the manifold pressure port provides the operator with a distinguishing pressure that is characteristic of the location of the distal region of the pacing lead thereby giving knowledge of the location of the distal region of the pacing lead to the operator. The side or end orifices can also be used for delivery of contrast medium or for delivery of a drug to the central (intracardio) circulation via the manifold port when it is connected, for example to a syringe. 
     If the pacing lead becomes dislodged at a later time period other than the initial lead placement setting, the pacing lead can be easily and safely repositioned to regain capture possibly under hemodynamic guidance without concern for lead perforation through the heart wall. Due to the curled atraumatic distal region and the multiplicity of cathode sites, a small adjustment of the pacing lead either via distal or proximal movement of the pacing lead body will result in electrical recapture of the myocardial via any one of the electrode sites found in the curled distal region. Repositioning of the pacing lead can occur either blindly or with hemodynamic echocardiographic or, if absolutely necessary, fluoroscopic guidance. 
     In one embodiment an echogenic coating is applied to the pacing lead body and to the distal coiled region of the pacing lead. The echogenic coating can aid in visualizing the pacing lead under echo guidance during initial placement or repositioning of the pacing lead. Portable echocardiographic image can be easily performed transthoracically at the bedside. 
     In another embodiment the anode of the present invention is provided as a component of the introducer sheath that provides passage for the temporary pacing lead at the access site into the vasculature of the body. The anode can be positioned as a portion of the outer surface of the introducer sheath in contact with adjacent soft tissue overlying the vascular entry site. This then can be electrically coupled to the temporary pulse generator. Alternately, the anode can be attached to the introducer sheath as a sticky patch electrode or a sticky flange electrode that is placed into contact with the subcutaneous tissue at the access site into the venous vasculature. A locking screw can also be located on the introducer sheath near the manifold to tighten down on the pacing lead and fix the lead position to avoid inadvertent lead migration within the heart that can result in loss of electrical capture. 
     Advantages are provided by a loop configuration for the coiled region of the temporary pacing lead including atraumatic contact with the myocardial wall and providing an outward force on the multiplicity of electrodes against the two opposing endocardial walls of the heart chamber to attain consistent capture of the electrical stimulation signal. Most embodiments of the present invention are not required to have a closed loop configuration in order to provide atraumatic contact with the myocardium and maintain effective and stable capture. An open loop distal can have numerous shapes and sizes to maximize good position on multiple sites. Such other embodiments without a closed loop provided by the embodiment with different shapes and sizes give the additional advantage for removal of the pacing lead from the heart chamber without potential for entanglement and potential disruption of cordae tendineae which would create an incompetent TV. The distal region of the curled shaft that forms the curled loop is formed with a low bending modulus material such that the curled loop is easily bent during removal of the pacing lead, still minimizing this risk. 
     The objects and advantages of the invention will appear more fully from the following detailed description of the preferred embodiment of the invention made in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a partially perspective plan view of a curled temporary pacing lead with a closed loop having a multiplicity of cathode electrodes in the right ventricle of the heart. 
         FIG.  1 B  is a plan view of a curled temporary pacing lead with an open loop. 
         FIG.  1 C  is a cross-sectional top view of the introducer sheath manifold and pacing lead manifold showing a sheath indicator and lead indicator to provide the ability to appropriately orient pre-curved distal catheter. 
         FIG.  2    is a plan view of a temporary pacing lead showing the multiplicity of cathodes in the distal region and their connection to the cathode conduction wire. 
         FIG.  3 A  is a plan view showing the distal region of a temporary pacing lead with a small overlap portion for the coiled shaft of a closed loop with a round shape. 
         FIG.  3 B  is a plan view showing the distal region of a temporary pacing lead with a large overlap portion for the coiled shaft of a closed loop with an oval shape. 
         FIG.  3 C  is a plan view showing the distal region of a temporary pacing lead with a large overlap portion for the coiled shaft of a closed loop. 
         FIG.  4    is a plan view showing the distal region of a temporary pacing lead with an echogenic coating located on the outer surface of the coiled shaft. 
         FIG.  5    is a plan view of a temporary pacing catheter crossing the heart annulus with a stylet contained in the central lumen. 
         FIG.  6    is a plan view of a temporary pacing catheter entering the heart chamber over a stylet within the central lumen. 
         FIG.  7 A  is a plan view of temporary pacing lead with a stylet in the lead central lumen and extending to the distal end of the lead. 
         FIG.  7 B  is a plan view of temporary pacing lead with a stylet in the lead central lumen and having the stylet retracted to allow the lead distal region to form a curled shaft. 
         FIG.  8 A  is a partially perspective view of a temporary pacing lead with an open distal end entering the heart chamber over a guidewire with a distal floppy end. 
         FIG.  8 B  is a partially perspective view of a temporary pacing lead with an open distal end advancing over a guidewire to the heart apex. 
         FIG.  8 C  is a partially perspective view of a temporary pacing lead with an open distal end advancing over a guidewire to form a closed loop. 
         FIG.  9 A  is a plan view of a temporary pacing lead having an open distal end and showing a guidewire passing through the lead central lumen. 
         FIG.  9 B  is a plan view of a temporary pacing lead having an open distal end and showing a guidewire being retracted to allow the lead distal region to form a closed loop. 
         FIG.  10 A  is a plan view of an introducer sheath having an anode attached near the manifold, the anode is a sleeve anode. 
         FIG.  10 B  is a plan view of an introducer sheath having an anode attached near the manifold, the anode is a flange anode. 
         FIG.  10 C  is a plan view of an introducer sheath having an anode attached near the manifold, the anode is a patch anode; the introducer has a locking screw to provide friction with a pacing lead body to prevent lead migration. 
         FIG.  11    is a plan view of a temporary pacing lead that is a bipolar lead that has a multiplicity of both cathode electrodes and anode electrodes in the curled shaft. 
         FIG.  12 A  is a plan view of a temporary pacing lead with a curled shaft showing an open loop. 
         FIG.  12 B  is a sketch that defines the term lead equilibrium loop angle. 
         FIG.  12 C  is a plan view of a distal region of a temporary pacing lead showing a lead equilibrium loop angle of 270 degrees. 
         FIG.  12 D  is a plan view of a distal region of a temporary pacing lead showing a lead equilibrium loop angle of 90 degrees. 
         FIG.  12 E  is a plan view of a distal region of a temporary pacing lead showing a lead equilibrium loop angle of zero degrees. 
         FIG.  12 F  is a plan view of a distal region of a temporary pacing lead demonstrating the definition of a lead bending modulus. 
         FIG.  12 G  is a plan view of a distal region of a temporary pacing lead showing a lead equilibrium loop angle of 360 degrees and having an overlap portion. 
         FIG.  13 A  is a partial perspective view of a temporary pacing lead positioned within a right ventricle and having a stylet contained within the lead central lumen; the lead contacts two walls of the right ventricle. 
         FIG.  13 B  is a plan view of a straight pacing stylet with a stiffer stylet proximal region and a more flexible stylet distal region. 
         FIG.  13 C  is a sketch that defines the term lead-stylet loop angle. 
         FIG.  13 D  is a plan view of a distal region of a lead-stylet curled shaft demonstrating the definition of a lead-stylet bending modulus. 
         FIG.  13 E  is a plan view of a distal region of a stylet with a stylet curled shaft showing a stylet radius of curvature. 
         FIG.  13 F  is a sketch that defines the term stylet loop angle. 
         FIG.  13 G  is a plan view of a distal region of a stylet curled shaft demonstrating the definition of a stylet bending modulus. 
         FIG.  13 H  is a cross-sectional top view of a lead manifold and stylet manifold showing a lead indicator and stylet indicator to provide alignment of the lead and the stylet. 
         FIG.  14 A  is a partial perspective view of a temporary pacing lead located in the apex of the heart with a removal stylet inserted in the lead central lumen to assist with removal of the pacing lead. 
         FIG.  14 B  is a plan view of a proximal region, distal region, and distal tip of a removal stylet. 
         FIG.  15 A  is a plan view of a proximal region and distal region of a vascular stylet. 
         FIG.  15 B  is a plan view of a distal region of a lead equilibrium loop of a temporary pacing lead. 
         FIG.  15 C  is a plan view of the pacing lead proximal and distal region having a vascular stylet inserted into the lead central lumen. 
         FIG.  16 A  is a plan view of a ventricular placement stylet. 
         FIG.  16 B  is a plan view of a lead distal region forming a lead equilibrium loop upon partial retraction of the ventricular placement stylet. 
         FIG.  16 C  is a plan view of a ventricular placement stylet having a stylet curled shaft. 
         FIG.  16 D  is a plan view of a lead distal region having a ventricular placement stylet inserted into the lead central lumen to form a lead-stylet radius of curvature. 
         FIG.  17    is a partially perspective view of a temporary pacing lead entering the heart annulus and also a view of the temporary pacing lead advanced into the heart apex and having an lead loop equilibrium radius of curvature. 
         FIG.  18    is a partially perspective view of a temporary pacing lead located in the heart apex and having a pacing stylet inserted into the lead central lumen to enlarge the radius of curvature to a lead-stylet radius of curvature to contact two walls of the heart chamber. 
         FIG.  19    is a partially perspective view of a temporary pacing lead located in the heart apex and having a removal stylet inserted into the lead central lumen to assist with removal of the lead from the heart chamber, preventing sub-tricuspid valve apparatus entanglement. 
         FIG.  20    is a perspective view of a lead distal region having a guidewire with a spiral loop or pig tail extending of the lead open distal end and allowing the lead and guidewire to be advanced safely into the heart chamber without echo guidance or fluoroscopic guidance. 
         FIG.  21 A  is a plan view of a temporary pacing lead having a control fiber that can be activated under tension to pull the lead distal end into contact with the lead body to form a closed loop; the lead is in a linear configuration to traverse the vasculature. 
         FIG.  21 B  is a plan view of a temporary pacing lead having a control fiber that can be activated under tension to pull the lead distal end into contact with the lead body to form a closed loop; the lead has formed a closed loop for entry into the heart annulus and for removal from the heart chamber to prevent sub-tricuspid apparatus entanglement. 
         FIG.  21 C  is a plan view of a temporary pacing lead having a control fiber that can be activated under tension to pull the lead distal end into contact with the lead body to form a closed loop; the lead is in an open loop configuration suitable for pacing the heart chamber. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG.  1 A  shows an embodiment of the present invention for a temporary pacing lead  5 . In this embodiment the pacing lead  5  is introduced through an introducer sheath  10  placed in the internal jugular vein (IJV)  15 ; the pacing lead  5  extends through the right atrium (RA)  20  and across the tricuspid valve (TCV)  25  and into the right ventricle (RV)  30  of the heart  35 . It is understood, however, that this invention applies also to other entry sites into the vasculature including the subclavian vein (SCV)  40 , the femoral vein (FV)  45 , the aorta  50 , or other blood vessels or conduits of the body; the pacing lead  5  can also be used to pace the RA  20 , left atrium (LA)  55 , left ventricle (LV)  60  or other chambers of the heart  35  or body. 
     As shown in  FIGS.  1 A and  2    the pacing lead  5  has a lead manifold  65  located outside of the body, the lead manifold  65  is attached to the lead body  70  which extends distally through the introducer sheath  10 . The lead body  70  of the pacing lead  5  extends distally to the lead distal end  75 . A curled shaft  80  is formed in the lead distal region  85  of the pacing lead  5 . The curled shaft  80  can have an open loop  90  as shown in  FIG.  1 B  or the curled shaft  80  can have a closed loop  95  as shown in  FIGS.  1 A and  2    (and which can be referred to as a coiled shaft  100 , a subgroup of a curled shaft  80 ). All structures for the coiled shaft  100  are understood to be included into the broader description of a curled shaft  80 , and hence reference names and reference numerals used to describe a coiled shaft  100  apply to a curled shaft  80  which includes other embodiments of the present invention described subsequently in the specification. 
     Curled Shaft  80  and Coiled Shaft  100   
     The curled shaft  80  comprised of a coiled shaft  100  has been positioned within the RV  30  and is ready for pacing of the RV  30  as shown in  FIG.  1 A . The coiled shaft  100  forms a closed loop  95  such that there is an overlap portion  105  that overlaps or extends adjacent to and in the same direction as another portion of the coiled shaft  100  to form a coiled or spiral shape and which is referred to herein as a closed loop  95 . The curled shaft  80  has a distally directed portion  110  that follows along the lateral wall  115  of the RV  30 , for example, and bends to contact or subtend the apex  120  of the heart  35 , a proximally directed portion  125  that follows along the septal wall  130  of the RV  30 , for example. A closing portion  135  and an overlap portion  105  completes the closed loop  95  of the coiled shaft  100  by coming into near proximity or contact with the distally directed portion  110 ; the lead distal end  75  does not extend outward into contact with the endocardial surface  140  of the myocardial tissue  142  of the heart  35 . Each portion of the coiled shaft  100  extends in a single plane as it forms its coiled or spiral shape. The lead distal end  75  of the pacing lead  5  of this embodiment is located in the overlap portion  105  of the coiled shaft  100  which extends with a radius of curvature that is less than the distally directed portion  110  and does not contact the endocardial surface  140 . At least some of the overlap portion  105  extends with a distal direction  145  similar to the distally directed portion  110  to form the closed loop  95 . As shown in  FIG.  1 A  the curled shaft  80  can be oriented within the RV  30  chamber such that the plane of the curled shaft  80  extends from the septal wall  130  to the lateral wall  115  or at any other orientation within the ventricular chamber. Orientation can be obtained by positioning a lead indicator  150  located on the lead manifold relative to a sheath indicator  155  located on the sheath manifold  160 , for example, as shown in  FIG.  1 C . 
     Materials Forming Lead Body  70   
     The pacing lead body  70  and curled shaft  80  are formed from materials found in existing pacing leads known to the art. An insulative polymer tubing formed from polyurethane or silicone, for example, can be used to form the lead body  70  and curled shaft  80  and retain the curled shape of the curled shaft  80 . The profile diameter of the insulative polymer tubing and for the curled shaft  80  is preferably 5 French (Fr) with a range of 4 Fr to 8 Fr. A shaped metal wire can be embedded within the wall of the tubing to assist in forming the curled shape of the curled shaft  80 . The shaped metal wire can be formed from Nitinol, Elgiloy, or other elastic material that can help retain the shape of the curled shaft  80 . Nitinol (an acronym for Nickel Titanium Naval Ordnance Laboratory) is a family of intermetallic materials, which contain a nearly equal mixture of nickel (55 wt. %) and titanium. Other elements can be added to adjust or “tune” the material properties. These materials are known to exhibit unique behavior, specifically, a well-defined “shape memory” and super elasticity. The curled shaft  80  has a curled shaft radius of curvature  165  of preferably 1-2 cm with a range of about 0.5-3 cm, such that it can traverse the TCV  25  and enter the RA  20  and matches the shape of the apex  120  and mid-cavity of the chamber of the heart  35 . The curled shaft radius of curvature  165  for the curled shaft  80  may be larger in the distally directed portion  110  than the proximally directed portion  125 ; the radius of curvature may become smaller as the curled shaft  80  extends from the distally directed portion  110  to the distal end  75  of the pacing lead  5 . 
     Cathode Sites  170   
     Located along the curled shaft  80  is a plurality of cathode sites  170  which have electrical continuity with each other; each electrode site is connected electrically via a cathode continuity member  175  to a cathode conduction wire  180  which extends along the pacing lead body  70  to the cathode connector  185  located on the lead manifold  65 . Each cathode site  170  can be formed by a ring electrode  190 , for example, which is placed around the insulative tubing  195  encircling the curled shaft  80 . The ring electrode  190  can be formed from platinum or other metal or metal alloy used to form pacing lead electrodes. The cathode conduction wire  180  can be formed from multi-filer metal coiled wire used in current pacing leads to transmit electrical signals through the lead body  70  and curled shaft  80  to each of the ring electrodes  190  located in the distal region  85  of the pacing lead  5 . Construction material for the cathode conduction wire  180  can be of a metal or metal alloy used in pacing leads currently found in the industry. The multiplicity of cathode sites  170  forms a single cathode electrode or cathode  320 . The number of cathode sites  170  can range from 2 to 20 and can be located along the distally directed portion  110 , the proximally directed portion  125 , or other portions of the curled shaft  80 . The cathode site spacing  200  between each of the cathode sites  170  or between each ring electrode  190  is enough to ensure that at least one cathode site or ring electrode  190  is able to make contact with the endocardial surface  140  such that capture of the signal from the ring electrode  190  is obtained. The cathode site spacing  200  is set at a distance of preferably 1 cm with a range of 0.5 cm-2 cm. The electrode area  202  of each ring electrode  190  or cathode site is such to provide a current density from the ring electrode  190  to the myocardium that will generate capture of the myocardium. The ring electrode length  205  for each ring electrode is preferably 3 mm with a range of 1 mm-5 mm. 
     Pulse Generator  220   
     The cathode connector  185  located on the lead manifold  65  is connected via a cathode connecting wire  210  to the negative pole  215  of a pulse generator  220 . The pulse generator  220  provides the voltage and current to the cathode electrode or cathode  320  found in the curled shaft  80  to provide temporary pacing for the patient. Standard pacing currents and voltages are used with the present invention as with standard pacing leads; adjustments can be made to the current to account for appropriate current density found for the multiplicity of cathode sites  170  to obtain appropriate myocardial capture of the electrical signal. When a specified current or voltage is delivered to the cathode  320 , the signal is received by the endocardial surface  140  of the myocardial tissue  142  and the electrical signal is transmitted through the myocardial tissue  142 ; the signal from the cathode  320  has then been captured by the myocardial tissue  142 . 
     Due to the multiplicity of cathode sites  170  contact of any one of the cathode sites  170  with the endocardial surface  140  can result in capture of the electrical signal from the pulse generator  220 . The multiplicity of cathode sites  170  allows the pacing lead  5  of the present invention to be positioned more easily within the chamber of the heart  35  since any one of the cathode sites  170  can effectively cause capture to occur. 
     The coiled shaft  100  located in the lead distal region  85  of one embodiment forms a closed loop  95  that is atraumatic to the patient and will not allow the distal end  75  of the pacing lead  5  to perforate the myocardial tissue  142  since the lead distal end  75  of this embodiment is not placed into contact with the myocardial tissue  142  as found in most of the current standard pacing leads. This atraumatic shape for the distal region  85  combined with the multiplicity of cathodes sites  170  allows the pacing lead  5  to be placed without fluoroscopic guidance or echo guidance due to the atraumatic shape of the distal region  85 . The present pacing lead  5  ensures a successful capture since the instant pacing lead  5  can obtain capture via any one of the multiplicity of cathode sites  170 . Echo guidance may be used primarily to assist with placement and assess lead positioning. Fluoroscopy is required for placement of present standard pacing leads to ensure that the pacing lead  5  lies along the endocardial surface  140  without perforation and for more precise positioning to obtain capture. 
     The curled shaft  80  found in the distal region  85  of the pacing lead  5  of the present embodiment also helps to provide an outward curled shaft applied force  225  to place the cathode sites  170  into intimate contact with the endocardial surface  140  of the heart  35 . The distally directed portion  110  of the curled shaft  80  and the proximally directed portion  125  of the curled shaft  80  helps to place an equal and opposite outward lead curled shaft applied force  225  onto two opposing walls of the RV chamber of the heart  35 . The outward curled shaft applied force  225  pushing the curled shaft  80  against the endocardial tissues helps to ensure capture of one of the cathodes sites  170  with the myocardium and prevent dislodgement of the cathode site  170  from their lodging adjacent to the myocardial tissue  142 . 
     In the circumstance that the cathode site  170  becomes dislodged at a later time period following the insertion of the temporary pacing lead  5 , the pacing lead  5  of the present invention is easily repositioned without the need for fluoroscopy and also without the need for echo guidance. Due to the curled-shaped distal region  85  and the multiplicity of cathode sites  170 , a small advancement of the lead body  70  in a distal direction  145  or retraction proximally will allow the previously captured cathode site  170  or a new neighboring cathode site  170  (or second cathode site) to make contact with the endocardial surface  140  and regain capture. 
     Shapes of the Curled Shaft  80   
     Various shapes for the curled shaft  80  have been contemplated; the curled shaft  80  can form a shape that approximates the internal endocardial surface  140  of the heart chamber  508 . As shown in  FIGS.  3 A- 3 C , the curled shaft  80  can be a coiled shaft  100 ; the amount of overlap portion  105  can involve only the distal end  75  of the pacing lead  5  as shown in  FIG.  3 A  or the overlap portion  105  can include a spiral that continues at a smaller radius of curvature as shown in  FIG.  3 C . The curled shaft  80  can be oval shaped as shown in  FIG.  3 B  or can be more rounded as shown in  FIG.  3 C . The curled shaft  80  can also be formed without an overlap portion  105  as discussed in later embodiments. 
     Echogenic coating  226  can be applied to the outer surface  228  of the lead body  70  and lead distal region  85  as shown in  FIG.  4    to enhance its ability to be visualized on echo guidance. For example microspheres can be adhered to or embedded into the outer surface  228  of the pacing lead  5  to reflect sound waves and enhance visualization. Alternately, echogenic materials that absorb, reflect, or generate sound waves can be located on the outer surface  228  of the pacing lead body  70  or lead distal region  85 . 
     Placement of Temporary Pacing Lead  5   
     Placement of the temporary pacing lead  5  of the present invention under echo guidance or without echo guidance is shown in  FIGS.  5  and  6    with the final placement as shown in  FIG.  1 A . As seen in  FIG.  5   , a linearly-shaped wire or probe such as a stylet  230 , for example, is slidingly placed within the lead central lumen  235  to cause the lead distal region  85  to form a generally linear shape. The radius of curvature for the distal region  85  with the stylet  230  inserted is greater than 10 cm. The stylet  230  is formed from a metal such as stainless steel, Nitinol, or other metal or composite and has a linear shape with a radius of curvature greater than 10 cm. The pacing lead  5  with the stylet  230  inserted is advanced through the introducer sheath  10  located in the internal jugular vein, IJV  15  along with the stylet  230  and across the tricuspid valve  25 . A transthoracic echo (TTE) probe can be used to view the passage of the pacing lead  5  and stylet  230  across the TCV  25  as shown in  FIG.  5   . 
     While holding the stylet  230  in a fixed position, the pacing lead  5  is advanced distally into the right ventricle, RV  30 . With the stylet  230  no longer located in the distal region  85 , the distal region  85  initiates the formation of a curled shaft  80  that extends into the RV as shown in  FIG.  6   . The curled shaft  80  has a curled shaft radius of curvature of preferably 1 cm with a range of 0.5-3.0 cm to fit within the TCV  25  and not snag the cordae tendineae  236  of the heart valve  238 . The lead distal end  75  of this embodiment has a closed distal end  240  that is a blunt rounded surface with no lead central lumen  235  extending therethrough and does not allow the stylet  230  or a stiff guidewire  290  to extend out of the lead distal end  75 . Further advancement of the pacing lead  5  while holding the stylet  230  at a fixed position allows the lead distal region  85  to form an equilibrium configuration of a closed loop  95  as shown in the coiled region of  FIG.  1 A  or an open loop  90  as shown in  FIG.  1 B . 
       FIGS.  7 A and  7 B  show an embodiment for the pacing lead  5  of the present invention having one or more orifices  245  located in the distal region  85  of the curled shaft  80 , i.e., between the lead distal tip  250  and the distal region  85  not containing the cathode sites  170 . The orifices  245  can be one or more side orifices  255  as shown in  FIGS.  7 A and  7 B  which extends through the curled shaft wall  260  and is in direct fluid communication with the lead distal lumen  265 . The distal lumen  265  forms a portion of the central lumen  235  that extends throughout the lead body  70  of the pacing lead  5 . The one or more orifices  245  should be smaller than the stylet diameter  266  to contain the stylet  230  within the distal lumen  265  but should provide a hydraulic diameter, i.e., a calculated diameter that is equivalent hydraulically to the distal lumen diameter  275 , that does not dampen a pressure signal from the blood from an outside region  268  outside of the curled shaft  80  to the distal lumen  265  of the pacing lead  5 . A manifold port  270  located on the lead manifold  65  is also in direct fluid communication with the lead central lumen  235  of the lead body  70 . A pressure transducer (not shown) can thereby be sealingly connected to the manifold port  270  and detect a pressure signal from the body fluid or blood that is located on the outside of the curled shaft  80  in the lead distal region  85  of the catheter body adjacent to the side orifice  255 . The operator can use the characteristic of the pressure signal which varies from the RA  20  to the RV  30 , for example, to determine the location of the lead distal region  85  while the pacing lead  5  is being delivered through the vasculature and into the heart chambers  508 . Identification can be made by the operator that the lead distal region  85  has been delivered to the RV  30 . Thus, the pacing lead  5  can be delivered to the RV  30  without using fluoroscopy if desired, and can be delivered under echo guidance, if desired, with the added assistance of observing the pressure signal that is characteristic of the desired delivery location for the distal region  85  within the heart  35  and vasculature. This establishes the opportunity to deliver the lead under hemodynamic guidance. 
     The location of the side orifice  255  or orifices  245  should be distal to the cathode sites  170  such that the pressure signal that is received from the operator indicates the pressure of the chamber into which the operator is entering, such as the RA  20  or RV  30 , for example. Also, as shown in  FIGS.  1 A and  7 B , the side orifice  255  or other pressure sensing orifices  245  should be located in the lead distal tip  250  such that as the curled shaft  80  is located in the ventricular chamber such as the RV  80 , the orifices  245  are positioned closer to the right atrium  20  and closer to the lead proximal region  272  than are the cathode sites  170  positioned to ensure that the cathode sites  170  are correctly and safely located near the apex  120  of the heart  35 . 
     As shown in  FIG.  7 A , the stylet  230  can be placed within the lead central lumen  235  to allow ease of delivery of the pacing lead  5  through the vasculature as described in  FIGS.  5  and  6   . During the delivery of the pacing lead  5  and after achieving a final location for the pacing lead  5  within the RV  30 , the operator can partially withdraw the stylet  230  out of the lead distal region  85 . The distal lumen  265  then becomes available for pressure signal transmission back to the manifold port  270 . The distal lumen diameter  275  needed to deliver the pressure signal without degradation or dampening of the pressure signal intensity is preferably 0.020 inches with a range 0.016-0.030 inches. The stylet  230  can reside in the proximal lumen  280  of the lead body  70  during pressure signal transmission; the proximal lumen  280  is a portion of the central lumen  235  that resides within the lead proximal region  272  of the lead body  70  and is located proximal to the curled shaft  80 . The annular space between the lead body  70  and the stylet  230  must provide a hydraulic diameter (i.e., a calculated diameter that is equivalent hydraulically to the distal lumen diameter  275 ) that is equal or greater than the distal lumen diameter  275 . Alternately, the stylet  230  can be pulled back out of the central lumen  235  such that the stylet  230  does not provide any reduction in area in the central lumen  235  that could be used for pressure signal transmission; such reduction in central lumen area could result dampening of the pressure signal that is being transmitted from the side orifice  255  to the manifold port  270 . 
     Alternate Embodiment—FIGS.  8 A- 8 C 
     An alternate embodiment for the pacing lead  5  of the present invention has an open distal end  285  as shown in  FIGS.  8 A- 8 C . As shown in  FIG.  8 A  a stylet  230  such as a guidewire  290 , for example, is first placed through the introducer sheath  10  and into the RV  30 . The guidewire  290  can have a guidewire stiff region  295  that is located within the introducer sheath  10  and extending across the TCV  25 . The guidewire stiff region  295  is intended to interface with the lead distal region  85  during delivery of the pacing lead  5  through the vasculature such that the lead distal region  85  becomes more linear or less curved, i.e., less curled, and can traverse the vasculature more easily to reach the RV of the heart  35 . A softer guidewire curled region  300  is located in the right ventricle, RV  30  and provides an atraumatic shape that is similar to the shape of the chamber walls and apex  120  of the RV  30 . Between the guidewire stiff region  295  and the guidewire curled region  300  is a guidewire transition region  305  that is intermediate both in shape and stiffness between the guidewire transition region  305  and the guidewire curled region  300 ; the guidewire transition region  305  has more curvature than the guidewire stiff region  295  and less curvature than the guidewire curled region  300 ; the guidewire transition region  305  is softer than the guidewire stiff region  295  and stiffer than the guidewire curled region  300 . As shown in  FIG.  8 A , the pacing lead  5  has been advanced over the guidewire  290  such that the open distal end  285  of the pacing lead  5  is located across the TCV  25  at a location near the guidewire junction  310  of the guidewire stiff region  295  and guidewire transition region  305 . 
     As shown in  FIG.  8 B  the guidewire  290  is held in a fixed position in space as the pacing lead  5  is advanced over the guidewire  290  into the RV  30 , around the apex  120  of the RV  30 , and directed proximally upward adjacent the septal wall  130 ; the guidewire  290 , as shown, is extending beyond the open distal end  285  of the pacing lead  5 . Further advancement of the pacing lead  5  is shown in  FIG.  8 C  with the guidewire  290  held fixed in position. The pacing lead  5  forms a curled distal region  85  due to its preformed curled shape and can form an overlap portion  105  of a closed loop  95 . The guidewire  290  can then be removed from the pacing lead  5  prior to activation of the pacing lead  5  or alternately can remain in place within the lead central lumen  235 . Various guidewire  290  shapes and lengths can be used without deviating from the present invention. For example, the guidewire  290  can have a complete coiled loop that overlaps with other portions of the guidewire  290 ; alternately a smaller length guidewire  290  that extends only a few centimeters into the RV can be used to deliver the pacing lead  5  of the present invention to the RV. 
     As shown in  FIGS.  9 A and  9 B  the open distal end  285  of the pacing lead  5  can provide an end orifice  315  that allows monitoring of blood pressure outside of the curled shaft  80  and within the vasculature of the body or heart  35 , or an orifice for delivery of contrast medium or drugs to a region outside of the curled shaft  80  such as the vasculature or heart chambers  508 . The open distal end  285  is in direct fluid communication with the manifold port  270  located on the lead manifold  65 . The pacing lead  5  can be delivered through the vasculature and into one or more chambers of the heart  35  over a guidewire  290  that extends through the lead body  70  from the lead manifold  65 , through the central lumen  235 , and out of the open distal end  285  of the pacing lead  5 . To deliver contrast medium or obtain a pressure signal from an outside region  268  outside of the curled shaft  80  adjacent to the open distal end  285  of the pacing lead  5 , the guidewire  290  can be pulled back such that it is located in the proximal lumen  280  of the pacing lead  5 . The distal lumen  265  of the pacing lead  5  should have a distal lumen diameter  275  of preferably 0.020 inches with a range of 0.016-0.030 inches to obtain an undamped pressure signal from the open distal end  285  to the manifold port  270 . The hydraulic diameter of the proximal lumen  280  should be similar to the distal lumen diameter  275 . Alternately, the guidewire  290  can be removed entirely from the central lumen  235  for delivery of contrast medium, delivery of drugs, or for measurement of pressure within a heart chamber  508  or within the vasculature adjoining the heart  35 . 
     The unipolar temporary pacing lead  5  of the present invention has a cathode  320  comprised of cathode sites  170  located within the pacing lead distal region  85 . In further embodiments the anode  325  is located as a component of the introducer sheath  10  as shown in  FIGS.  10 A- 10 C . In  FIG.  10 A  the anode  325  is a sleeve anode  330  formed from a metal film that is located around a portion of the introducer sheath  10  that is near the sheath manifold  160  and is in contact with the subcutaneous tissue, the tissue tract, or the vasculature in which the introducer sheath  10  is inserted. The sleeve anode  330  is attached to an anode connector  335  located on the sheath manifold  160 . The anode connector  335  is connectable via an anode connecting wire  340  to the positive pole  345  of a pulse generator  220  as shown in  FIG.  1 A . The sleeve anode  330  can be formed from platinum, silver, or other metal or metal alloys that provide for efficient electrical signal transmission. As shown in  FIG.  10 B  the anode  325  can be a flange anode  350  that is joined or attached to the introducer sheath  10  and forms an electrical continuity with an anode connector  335  located on the sheath manifold  160 . The flange anode  350  can be formed from standard metals used to transmit electrical signals; the flange electrode is attached to the subcutaneous tissue via adhesive that is conductive. Another embodiment for the anode  325  is shown in  FIG.  10 C ; a patch anode  355  is electrically coupled to the anode connector  335  located on the sheath manifold  160 . The patch anode  355  is attached to the subcutaneous tissue near the access site; the patch electrode is formed from materials similar to those described for the flange electrode. Located on the introducer sheath  10  of the present invention and shown in  FIG.  10 C  is a locking screw  360  that is rotationally activated by the operator to apply a frictional force of a locking plate  365  into direct contact with a pacing lead body  70  that would pass within the introducer sheath. The frictional force between the locking plate  365  and the pacing lead body  70  would prevent inadvertent movement of the pacing lead  5  relative to the introducer sheath  10  thereby reducing the likelihood of loss of capture by a cathode site  170  of the pacing lead  5  with the endocardial surface  140  due to movement of the pacing lead body  70 . Other mechanical mechanisms are anticipated to apply a frictional force from the locking plate  365  to the lead body  70  to prevent movement of the pacing lead body  70  relative to the introducer sheath. 
     In a further alternate embodiment for the present pacing leads having a curled shaft  80 , the cathode sites  170  that have been presented in earlier embodiments of the temporary unipolar pacing lead  370  can instead consist of alternating cathode sites  170  and anode sites  380  thereby transforming the unipolar pacing lead  370  of  FIG.  2    into a bipolar pacing lead  375  as shown in  FIG.  11   . Each anode site  380  of the bipolar lead  375  of this embodiment is connected electrically via an anode continuity member  385  to the anode conduction wire  390  that extends via its own electrically insulated path through the lead body  70  to the lead manifold  65  where the anode conduction wire  390  forms an electrical continuity with an anode connector  335 . The anode connector  335  is connectable to an anode conduction wire  390  that can be connected to the positive pole  345  (see  FIG.  1 A ) of the pulse generator  220 . The cathode site  170  is electrically connected to the cathode conduction wire  180  as described in earlier embodiments. The cathode sites  170  and the cathode conduction wire  180  are each electrically insulated from the anode sites  380  and the anode conduction wire  390 . The bipolar pacing lead  375  of this embodiment has a similar curled shaft  80  located in the distal region  85  that is similar to the curled shaft  80  that has been discussed for the unipolar pacing lead  370  shown in  FIG.  1 A . The anode-cathode site spacing  395  between an anode site  380  and a neighboring cathode site  170  is similar to that provided in current standard pacing leads in order to provide current density to obtain and maintain capture; the anode-cathode site spacing  395  is 1 cm (range 0.5 cm to 2 cm). The paired site distance  405  between the anode-cathode paired sites  400  and a neighboring anode-cathode paired site  400  is 1 cm (range 0.5 cm to 2 cm) and is close enough such that small movements of the pacing lead  5  will allow one anode  325  and one neighboring cathode  320  to become an anode-cathode paired site  400 . The coiled shaft  100  plus the multiplicity of anode-cathode paired sites  400  located along the coiled shaft  100  would confer both safety to the pacing lead  5  due to the atraumatic coiled shape of the distal region  85  as well as ease of forming a capture of the myocardium by at least one anode-cathode paired site  400 . 
     It is further understood that each anode site  380  can be connected to a specific anode conduction wire  390  that extends to a specific anode connector  335  located on the lead manifold  65 ; thus the lead would contain a multiplicity of anode connectors  335  that are electrically insulated from each other and individually connectable to a multiplicity of anode connecting wires  340  to the pulse generator  220 . Similarly each cathode site  170  can be connected to a specific cathode conduction wire  180  that extends to a specific cathode connector  185  located on the lead manifold  65 ; thus the lead would contain a multiplicity of cathode connectors  185  that are electrically insulated from each other and individually connectable to a multiplicity of cathode connecting wires  210  to the pulse generator  220 . The pulse generator  220  is able to use an individual anode-cathode paired site  400  to detect a proper location for delivery of a temporary pacing signal. An individual anode-cathode paired site  400  located on the curled shaft  80  could then be activated by the pulse generator  220  in a specific region of the heart chamber  508  that is suitable for temporary pacing in a manner that obviates a potential for diaphragmatic capture, for example. 
     The previous embodiments of the present invention have shown a curled shaft  80  in a configuration of a coiled shaft  100  that has formed a closed loop  95  with an overlap region and hence the curled shaft  80  of some embodiments can have a coiled shaft  100 . Embodiments of the present invention are not required to have a lead closed loop  95  forming an overlap portion  105  extending from the lead distal end  75  to the distal region  85  of a curled shaft  80 . Embodiments that do not have a closed loop  95  may instead have an open loop  90  in a lead curled shaft  80  of the lead distal region  85 . The lead open loop  90  provides such embodiments with an improved capability to remove the lead curled shaft  80  from the heart chamber  508  following the temporary pacing procedure without snagging and potentially tearing a cordae tendineae  236  of a heart valve  238 . The embodiments having the open loop  90  also can be introduced into the chamber of the heart  35  in an atraumatic manner that does not injure the endocardial surface  140  of the heart chamber  508 . The embodiments of the temporary pacing lead  5  having an open loop  90  are intended to contain the multiple cathode electrodes  170  or anode electrodes  325  as described in the previous embodiments, the electrodes can be unipolar electrodes or bipolar electrodes as described in earlier embodiments. Additionally, the pacing lead  5  is configured as described in previous embodiments to measure blood pressure via a side orifice  255  or end orifice  315  to detect and identify the chamber of the heart in which the lead distal tip  250  resides. The pacing lead  5  having an open loop  90  can have a closed distal end  240  as shown in some embodiments, or the pacing lead  5  can have an open distal end  285  as described other embodiments such as those shown in  FIGS.  8 A- 8 C and  9 A- 9 B . 
     Lead in a Lead Equilibrium Configuration 
       FIGS.  12 A- 12 F  show embodiments for the lead body  70  of the present invention in a lead equilibrium configuration with a lead equilibrium loop  410 , i.e., a lead loop without a stylet  230  contained within the lead central lumen  235 , and having a lead open loop  90 . The lead body  70  has a linearly shaped lead proximal region  272  and a lead curled shaft  80  in the lead distal region  85 . The lead curled shaft  80  forms a lead open loop  90  with a lead loop equilibrium radius of curvature  415  of preferably 1 cm and in the range of 0.5-2.0 cm for the lead equilibrium loop  410 , i.e., the lead loop equilibrium configuration, such that a stylet  230  is not contained within the lead distal region  85 . The lead equilibrium loop angle  420  for the lead equilibrium loop  410 , i.e., without a stylet  230 , describes the amount of curvature or curl found in the lead curled shaft  80  due to its formed equilibrium shape as shown in  FIG.  12 B . The lead loop angle  420  for the lead equilibrium loop  410  or other lead loop is the amount of curvature or curl as identified by the lead proximal region direction  425  relative to the lead distal end direction  430 . The lead loop angle  420  as shown in  FIG.  12 A  is 180 degrees since the loop distal end direction is 180 degrees opposed from the lead proximal region direction  425  at the lead body junction  435  between the lead proximal region  272  and lead distal region  85 . The range for the lead equilibrium loop angle  420  is zero to 360 degrees; a smaller lead equilibrium loop angle  420  provides a greater advantage for removing the lead with an open loop  90  from the heart chamber  508  without entanglement with or tearing of the cordae tendineae  236 . The lead loop equilibrium angle of 180 degrees, and ranging from 150-240 degrees, provides an advantageous balance between an atraumatic contact with the endocardial surface  140  during pacing and ease of removing the lead curled shaft  80  from the heart chamber  508  without tearing the cordae tendineae  236 . Various lead equilibrium loop angles  420  are anticipated and depicted in  FIGS.  12 C- 12 E ;  FIG.  12 C  shows a lead distal region  85  with a lead equilibrium loop angle  420  of 270 degrees;  FIG.  12 D  shows a lead equilibrium loop angle  420  of 90 degrees;  FIG.  12 E  shows a lead equilibrium loop angle  420  of zero degrees; variation of the lead equilibrium loop angle  420  are understood to be included in the present invention. It is noted in  FIG.  12 G  that the lead equilibrium loop angle  420  can be 360 degrees as shown in  FIG.  12 G , where the lead distal tip  250  forms an overlap portion  105  within the lead distal region  85  as described in earlier embodiments of the present invention. 
     The lead proximal region  272  is stiffer than the lead distal region  85 ; the lead proximal region  272  is able to provide the necessary push characteristics to allow the lead to be advanced within the vasculature and into the chamber of the heart  35 . The lead distal region  85  has a lead bending modulus as defined by  FIG.  12 F  of 0.6 Newtons (range 0.1-5.0 Newtons) and provides the distal region  85  with a soft and floppy characteristic that allows ease of bending. The lead bending modulus preferably ranges from 0.1-1.0 Newtons due to the more advantageous lead removal characteristics for a lead bending modulus that ranges from 0.1-1.0 Newtons. The low lead bending modulus of 0.6 Newtons (range 0.1-1.0 Newtons) allows the lead curled shaft  80  to bend and conform to the surface of the heart chamber  508  without causing tissue ischemia or necrosis at the contact of the curled shaft  80  with the endocardial surface  140 . The soft, floppy lead distal region  85  allows the lead to be removed from the heart chamber  508  without entanglement with the cordae tendineae  236  and without tearing the cordae tendineae  236 . As shown in  FIG.  12 F  a lead shaft length  440  of the lead curled shaft  80  requires a lead applied force  445  acting perpendicular to the shaft central axis  450  at the lead distal end  75  to generate a lead displacement  455 . The ratio of lead displacement  455  per lead shaft length  440  is equal to the lead bending strain of the lead curled shaft  80 . The lead bending modulus is equal to: (lead applied force  445 )/lead bending strain. Thus for the lead curled shaft  80  the amount of lead applied force  445  to cause a lead curled shaft  80  with a lead bending modulus of 0.6 Newtons to bend to a lead displacement  455  of 1 cm over a 1 cm lead shaft length  440  is 0.6 Newtons. As shown in  FIG.  12 F , the lead shaft length is shown to be a linear configuration for illustrational purposes. It is understood that similar principles for bending modulus determination apply to a lead curled shaft  80  with a curved or curled shape that is then further bent to an alternate radius of curvature. 
       FIGS.  13 A- 13 G  show embodiments of a pacing lead  5  with a lead open loop  90  located within an RV  30  chamber  508  of the heart; a stylet  230  is located in the lead central lumen  235 . The stylet  230  is a pacing stylet  460  that can be maintained within the lead central lumen  235  during pacing.  FIG.  13 A  shows a lead distal region  85  located within the right ventricle  30  of the heart  35 , for example, and making contact with the endocardial surface  140  of the RV. A straight stylet such as that shown in  FIG.  13 B  can be placed within the lead central lumen  235  (of the lead of  FIG.  12 A , for example) to cause an outward lead-stylet applied force  465  onto the endocardial surface  140  to provide definite contact of the cathode sites  170  of the cathode electrode  320  with the endocardial surface  140  obtain and maintain capture of the electrical signal. 
     The stylet  230  has a stylet manifold  470  located at its proximal end to assist in placement depth of the stylet  230  within the lead central lumen  235  and provide rotation of the stylet  230  for rotational alignment of the stylet  230  relative to the lead body  70 . The lead-stylet loop  475  has a lead-stylet loop radius of curvature  280  (with the stylet  230  inserted into the lead central lumen  235  and extending to the lead distal end  75 ) that is 1.5 cm (range 1.0-3.0 cm). The lead-stylet loop angle  481  for the lead-stylet loop  475  as shown in  FIGS.  13 A and  13 C  is 180 degrees to provide atraumatic contact with two walls of the endocardial surface  140  and provide an outward lead-stylet applied force  465  in opposite directions against the two opposing walls of the heart chamber  508 . The lead-stylet loop angle  481  extends from the lead-stylet distal end direction  482  to the lead-stylet proximal region direction  483  and can range from 150 degrees to more than 360 degrees with the stylet  230  inserted. The lead-stylet loop radius of curvature  280  should be at least 1 cm in order to provide definite contact with the endocardial surfaces  140  on two sides of the heart chamber  508 ; the lead-stylet loop radius of curvature  280  can be larger, for example, with a lead-stylet loop radius of curvature  280  of up to 3.0 cm. 
     A straight pacing stylet  460  with a stiffer stylet proximal region that the stylet distal region  485  can provide a larger outward lead-stylet applied force of the lead curled shaft  80  onto the endocardial surface  140  of the heart  35  than a softer stylet distal region  485 . The stiffer stylet distal region  485  can be obtained by a larger diameter for the stylet distal region  485  or by altering the temper of a metallic stylet or by altering the material properties of the stylet distal region  485 . The outward lead-stylet applied force  465  of the combined lead curved shaft and the stylet curved shaft onto the endocardial surface  140  of the heart  35  is 0.6 Newtons (range 0.1-5 Newtons); preferably, the outward lead-stylet applied force  465  against the endocardium is 0.1-1.0 Newtons; a larger outward force against the endocardial surface  140  providers better contact of the lead distal region  80  with the endocardial surface  140  but can cause unwanted tissue ischemia and necrosis. 
     The outward lead-stylet applied force  465  provided by the combined material elasticity of the lead curled shaft  80  and the stylet curled shaft  490  (i.e., the lead-stylet curled shaft  488 ) is determined by the combined lead-stylet bending modulus of the lead curled shaft  80  and the stylet curled shaft  490  as shown in  FIG.  13 D . The ratio of lead-stylet displacement  495  per lead-stylet shaft length  500  is equal to the lead-stylet bending strain of the lead-stylet curled shaft  488 . The lead-stylet bending modulus is equal to: (lead-stylet applied force  465 )/lead-stylet bending strain. Thus for the lead-stylet curled shaft  488  the amount of lead-stylet applied force  465  to cause a lead-stylet curled shaft  488  with a lead-stylet bending modulus of 0.6 Newtons to bend to a lead-stylet displacement  495  of 1.5 cm over a 1.5 cm shaft length is 0.6 Newtons. The bending modulus for the stylet distal region  485  is 0.6 Newtons (range 0.1-5.0 Newtons, and preferably 0.1-1.0 Newtons) such that the lead-stylet outward applied force against the endocardium is controlled to 0.6 Newtons (range 0.1-1.0 Newtons). As shown in  FIG.  13 D , the lead-stylet shaft length  500  is shown to be a linear configuration for illustrational purposes. It is understood that similar principles for bending modulus determination apply to a lead-stylet curled shaft  488  with a curved or curled shape that is then further bent to an alternate radius of curvature. 
     The pacing stylet  460  can have other configurations other that those shown in  FIG.  13 B . For example, as shown in  FIG.  13 E , the pacing stylet  460  can have a stylet radius of curvature  505  of 2.0 cm and can be placed into a lead open loop  90  with a lead loop equilibrium radius of curvature  415  of 1 cm such as shown in  FIG.  12 A  and form a lead-stylet loop  475  with a lead-stylet loop radius of curvature  280  or 1.5 cm, for example, as shown in  FIG.  13 A . A lead-stylet radius of curvature of preferably 1.5 cm with a range of 1-3 cm will provide suitable contact of the pacing lead  5  with the endocardial surface  140  of the heart chamber  508  and provide electrical signal capture. The stylet radius of curvature  505  can range from 1 cm (for a lead loop equilibrium radius of curvature  415  that is larger than 3 cm, for example) to infinity or a straight stylet, for example, for use in a lead loop equilibrium radius of curvature  415  that is smaller than the heart chamber width  510 . The average heart chamber width  510  at a location of contact with the pacing lead body  70  is typical 3 cm with a range of 1-5 cm. The pacing stylet  460  can have a stylet loop angle  515  as described by  FIG.  13 F  that extends from a stylet proximal region direction  520  to a stylet distal end direction  525  of preferably 180 degrees with a range of zero to 360 degrees. 
     The stylet has a stylet bending modulus that is determined by a stylet applied force  530  causing the stylet distal end  535  to bend over a stylet shaft length  540  of the stylet shaft as shown in  FIG.  13 G . The ratio of stylet displacement  545  per stylet shaft length  540  is equal to the stylet bending strain of the stylet curled shaft  490 . The stylet bending modulus is equal to: (stylet applied force  530 )/stylet bending strain. Thus for the stylet curled shaft  490  the amount of stylet applied force  530  to cause a stylet curled shaft  490  with a stylet bending modulus of 0.6 Newtons to bend to a stylet displacement  545  of 1 cm over a 1 cm stylet shaft length  540  is 0.6 Newtons. As shown in  FIG.  13 F , the stylet shaft length is shown to be a linear configuration for illustrational purposes. It is understood that similar principles for bending modulus determination apply to a stylet curled shaft  490  with a curved or curled shape that is then further bent to an alternate radius of curvature. 
     The stylet of the present invention can have a stylet bending modulus in the stylet distal region  485  that ranges from 0.1-5 Newtons and preferably ranges from 0.1-1.0 Newtons to more closely equal and balance the bending modulus of the lead distal region  85  and provide a suitable outward lead-stylet applied force  465  that does not generate trauma to the endocardial surface  140 . The outward lead-stylet applied force  465  will also provide a more linear relationship with respect to lead-stylet displacement  495  if the lead bending modulus and lead loop equilibrium radius of curvature  415  is similar in magnitude to the stylet bending modulus and stylet radius of curvature  505 . Thus, the stylet radius of curvature  525 , the stylet bending modulus, and the stylet loop angle  515  are combined with the lead loop equilibrium radius of curvature  415 , the lead bending modulus, and the lead equilibrium loop angle  420  to determine the lead-stylet loop radius of curvature  480 , the lead-stylet loop angle  481 , and the outward lead-stylet applied force  465  onto the endocardial surface  140  of the heart  35 . 
     The outward stylet applied force  530  can act in the same outward direction as an outward lead applied force  445 , acting against the endocardial surface  140 , and hence the two forces are addictive. If the lead curled shaft  80  is of a smaller lead loop radius of curvature than the stylet loop radius of curvature, then the stylet applied force  530  can be acting to enlarge the lead loop radius of curvature and the lead applied force  445  is acting in a direction opposed to the stylet curled shaft  490 . The outward forces of the lead applied force  445  and the stylet applied force  530  are expected in the present invention to provide a combined outward lead-stylet applied force  465  onto the endocardial surface  140  of 0.6 Newtons (range 0.1-5.0 Newtons, and preferred range of 0.1-1.0 Newtons) to ensure that tissue ischemia and necrosis of the myocardial tissues  145  are not generated. 
     For the embodiment wherein the lead curled shaft  80  has a lead loop equilibrium radius of curvature  415  of 1 cm and a stylet has a stylet radius of curvature  505  of 2 cm as described in  FIG.  13 E , the lead-stylet loop radius of curvature  280  could be 1.5 cm provided that the stylet curled shaft  490  aligned in the same plane and with the same coil direction as the lead curled shaft  80 . Such alignment tends to occur naturally as the operator inserts the stylet into the lead central lumen  235 . However, if the operator is intending to place the stylet into the lead central lumen  235  such that the lead curled shaft  80  is directly opposed to the stylet curled shaft  490  (i.e., the direction of the stylet loop forms a spiral in a direction that is opposite to the lead loop direction) then an indicator can be located on the stylet manifold  470  and the lead manifold  65  to assist the operator in obtaining the alignment direction that is desired to obtain contact of the lead distal region  80  with the endocardial surface  140  without causing tissue ischemia or necrosis. As shown in  FIG.  13 H  a lead indicator  150  located on the lead manifold  65  can be oriented relative to a stylet indicator  555  located on the stylet manifold  470  to place the orientation of the lead curled shaft  80  in alignment with the stylet curled shaft  490 . A locking means such as a screw-type mechanism can be incorporated into the lead indicator  150  and stylet indicator  555  to lock a specific orientation. 
     Removal of the temporary pacing lead  5  from the chamber of the heart  35  is accomplished by inserting a stylet  230  that can be a removal stylet  560  such as that shown in  FIGS.  14 A and  14 B  into the lead central lumen  235  as shown in  FIG.  14 A . The stylet has a linearly configured stylet proximal region  486  and also a linear stylet central region  487  that extends within a portion of the lead distal region  85 . The removal stylet  560  has a curled stylet distal tip  535  that is of a lower bending modulus than the stylet proximal region  486  or stylet central region  487 ; the stylet distal end  535  can be advanced to a position short of approximation with the lead distal end  75 . The stylet serves to straighten a portion of the lead distal region  85  located in the chamber of the heart  35 ; the stylet distal tip serves as a transition region to allow the lead to be retracted under tension over the stylet  230  until the stylet distal end  535  contacts the lead distal end  75  and further retracted out of the heart chamber  508  along with the stylet  230  such that the lead curled shaft  80  does not entangle with cordae tendineae  236  of the heart chamber  508  as the lead is being retracted under tension. 
     Introduction of the temporary pacing lead  5  into the vasculature requires that much of the lead body  70  is generally straight except for a curved lead distal tip  250  that can help to negotiate turns within the vasculature and prolapse safely across the TCV. To accomplish the traversal within the vasculature, a generally straight vascular stylet  565  as shown in  FIG.  15 A  can be inserted, for example, into a lead body  70  with an equilibrium configuration as shown in FIG.  15 B to provide a combined lead-stylet configuration as shown in  FIG.  15 C . The lead loop equilibrium radius of curvature  415  can be, for example, 1 cm. The stylet can be stopped proximal to the lead distal tip  75  such that the curled shape of the lead curled shaft provides a small curvature that enables negotiation of vascular turns. 
     Advancement of the temporary pacing lead  5  into the chamber of the heart  35  requires that the configuration of the curled shaft  80  be rounded and atraumatic to the endocardial surface  140 . A proximal secondary bend in the catheter or stylet can give directionality to the lead directing it toward the tricuspid valve annulus and thus entry into the RV. Also, the lead curled shaft  80  must be suitable to traversing the vasculature with a curled shaft  80  suitable to traverse the annulus  568  of the heart  35  and enter the heart chamber  508 . The lead loop equilibrium radius of curvature  415  of 1 cm allows the lead curled shaft  80  to form the lead loop within the RA. Withdrawal of the vascular stylet  565  (while maintaining a fixed position for the lead body  70 ) which can then also serve as a ventricular placement stylet  570  as shown in  FIGS.  16 A and  16 B  allows the lead distal region  85  to form a lead equilibrium loop  410  that is suitable (in both a small radius of curvature and a rounded shape) for entering into the heart chamber  508 . The lead curled shaft  80  must fit through a 2 cm diameter annulus  568  leading into the ventricular chamber and must have an atraumatic curled configuration that cannot produce trauma to TCV  25  or the endocardial surface  140  of the heart chamber  508 . Alternately, to obtain a lead-stylet loop radius of curvature  280  that is smaller than the lead loop equilibrium radius of curvature  415 , a shaped ventricular placement stylet  570  having a stylet loop  575  in the stylet curled shaft  490  with a stylet radius of curvature  505  of 0.5 cm, for example, can be introduced into the lead central lumen  235  to cause the lead-stylet loop radius of curvature  480  to be 0.75 cm, for example, as shown in  FIGS.  16 C and  16 D . 
     The method of use for the temporary pacing lead  5  of the present invention is shown in  FIGS.  17 - 19   . In  FIG.  17    the lead distal region  85  has been delivered to the RA  20  and the vascular stylet  565  has been withdrawn allowing the lead curled shaft  80  to form an atraumatic shape within the RA as shown in the RA  20  portion of  FIG.  17   . A ventricular placement stylet  570  may be introduced into the lead central lumen  235 , if desired, to form a different lead-stylet curled loop. The pacing lead  5  is then advanced to the apex  120  of the right ventricle, RV  30  also shown in the RV  30  portion of  FIG.  17   . The lead curled shaft  80  of the lead distal region  85  may obtain a lead loop equilibrium radius of curvature  415  if a stylet is not introduced into the lead distal region  85 . If the loop equilibrium radius of curvature is able to provide capture of an electrical signal to the myocardium, then temporary pacing is initiated. If additional outward force or additional outward displacement is needed by the lead curled shaft  80  to make contact with the heart chamber surface, then a pacing stylet  460  is introduced into the lead body central lumen  235  as shown in  FIG.  18   . The pacing stylet  460  can increase (or decrease; a decrease occurring if the stylet radius of curvature  505  is smaller than the lead loop equilibrium radius of curvature  415 ) the lead-stylet loop radius of curvature  280  and increase (or decrease; a decrease occurs if the stylet radius of curvature  505  is smaller than the lead-stylet loop radius of curvature  480 ) the outward force placed onto the endocardial surface  140 . Upon completion of temporary pacing, a removal stylet  560  can be placed into the lead central lumen  235  such that a generally linear portion of the stylet extends into the lead distal region  85  to help straighten the lead curled shaft  80  and assist with ease of lead removal. The lead body  70  can be withdrawn proximally under tension while maintaining position of the removal stylet  560  within the lead central lumen  235 . The lead curled region distal end  75  is withdrawn toward the stylet distal end  535  such that the lead curled region does not entangle or tear the cordae tendineae  236  as shown in  FIG.  19   ; then, the pacing lead body  70  and stylet  230  can be withdrawn together out of the heart chamber  508 . The soft, floppy lead distal region  85  allows the pacing lead  5  to be removed from the heart chamber  508  without entangling the cordae tendineae  236 . 
     The temporary pacing lead  5  having an open loop  90  can have an open distal end  285  as shown in  FIG.  20   ; the lead structure for this embodiment has been described earlier in  FIGS.  8 A- 8 C and  9 A- 9 B  and also in other embodiments. The stylet that has been described in earlier embodiments to alter the lead loop radius of curvature and alter the outward forces provided by the lead distal region  85  against the myocardial surface can be a guidewire  290 . The stylet  230  can be a shaped guidewire  290  that provides atraumatic passage of the lead body  70  over the guidewire  290  through the vasculature, into the heart chamber  508 , and during removal of the pacing lead  5  from the chamber of the heart  35 . The guidewire  290  can also have a guidewire coiled distal tip  580  or pig-tail, the guidewire coiled tip can be placed adjacent and distal to the lead distal end  75  to provide an atraumatic lead-wire configuration to the lead distal end  75  that allows the lead and guidewire  290  to be advanced together into the chamber of the heart  35  without a need for fluoroscopic guidance. 
     Control Fiber  585   
     A further embodiment for the pacing lead  5  of the present invention having multiple electrodes  170 , distal pressure measuring capability, and a lead closed loop  95  is shown in  FIGS.  21 A- 21 C .  FIG.  21 A  shows the lead distal region  85  of the lead body  70 ; a control fiber  585  is attached to the lead distal end  75  and traverses external to the lead distal region  85 . The control fiber  585  enters a control opening  590  at the lead body junction  435  of the lead proximal region  272  and lead distal region  85 . The control fiber  585  extends through a control fiber lumen  595  within the lead proximal region  272  to a lead manifold  65  located at the proximal end of the lead body  70 . A holding-tensioning member  600  is attached to the lead manifold  65 . The holding-tensioning member  600  is able to take up length of the control fiber  585  and provide tension to the control fiber  585 . As shown in  FIG.  21 A , the lead body  70  is in a linear configuration to traverse the introducer sheath  10 . A stylet  230  can be introduced into the lead body central lumen  235  as described in earlier embodiments. The control fiber  585  provides a tension from the lead distal end  75  to the control opening  590  that provides a lead loop controlled radius of curvature  605  to the lead distal region  85  of the lead body  70  as illustrated in  FIG.  21 B . 
     Once the lead distal end  75  has traversed through the vasculature and reached the right atrium  20  or the annulus  568  leading to the heart chamber  508 , the control fiber  585  can be activated by applying tension via the holding-tensioning member  600 . Application of tension causes the lead distal region  85  to form a closed loop  95  as shown in  FIG.  21 B . The closed loop  95  has a lead loop controlled radius of curvature  605  that allows entry of the closed loop  95  into the chamber of the heart  35  in an atraumatic manner. 
     Once the lead distal region  85  has been advanced into the chamber of the heart  35 , the control fiber  585  can be released to allow the lead distal region  85  to form a curled shaft  80  having loop  90  which remains closed by virtue of the tensioning fiber attachment at the distal lead tip  75  and a fiber controlled opening  590  as shown in  FIG.  21 C . The outward lead applied force  445  provided by the lead distal region  85  due to the bending energy stored in the lead distal body  70  causes contact between the electrode sites  170  and the endocardial surface  140 . The outward lead applied force  445  can be adjusted by introducing a stylet, if necessary, as described in earlier embodiments to provide an outward force of preferably 0.6 Newtons with a range of 0.1-5.0 Newtons. The outward applied force is preferred to have an upper range limit of 1.0 Newtons to ensure that the heart chamber  508  tissue does not become ischemic. Alternatively, the control fiber  585  can be released an additional amount or can be retracted under tension to alter the outward lead applied force  445  inherent in the stored bending energy of the lead distal region  85  onto the endocardial surface  140 . 
     Removal of the pacing lead  5  is accomplished by applying tension to the control fiber  585  via the holding-tensioning member  600  to place the lead distal region  85  into a closed loop  95  as shown in  FIG.  21 B . The pacing lead  5  can be pulled back under tension into the RA  20  where the control fiber  585  can be released to allow the lead distal region  85  to form a linear configuration as shown in  FIG.  21 A . Alternately, the control fiber  585  can be released of all tension within the heart chamber  508  allowing the lead body  70  to assume a more linear shape similar to that of  FIG.  21 A  prior to removing the lead body  70  from the heart chamber  508 . Since the lead distal tip  250  is attached to the lead body  70  via the control fiber  585  at the control fiber opening  590 , entanglement of the lead distal region  85  with cordae tendineae  236  is obviated. 
     Any version of any component or method step of the invention may be used with any other component or method step of the invention. The elements described herein can be used in any combination whether explicitly described or not. 
     All combinations of method steps as used herein can be performed in any order, unless otherwise specified or clearly implied to the contrary by the context in which the referenced combination is made. 
     As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. 
     Numerical ranges as used herein are intended to include every number and subset of numbers contained within that range, whether specifically disclosed or not. Further, these numerical ranges should be construed as providing support for a claim directed to any number or subset of numbers in that range. For example, a disclosure of from 1 to 10 should be construed as supporting a range of from 2 to 8, from 3 to 7, from 5 to 6, from 1 to 9, from 3.6 to 4.6, from 3.5 to 9.9, and so forth. 
     All patents, patent publications, and peer-reviewed publications (i.e., “references”) cited herein are expressly incorporated by reference in their entirety to the same extent as if each individual reference were specifically and individually indicated as being incorporated by reference. In case of conflict between the present disclosure and the incorporated references, the present disclosure controls. 
     The devices, methods, compounds and compositions of the present invention can comprise, consist of, or consist essentially of the essential elements and limitations described herein, as well as any additional or optional steps, ingredients, components, or limitations described herein or otherwise useful in the art. 
     While this invention may be embodied in many forms, what is described in detail herein is a specific preferred embodiment of the invention. The present disclosure is an exemplification of the principles of the invention is not intended to limit the invention to the particular embodiments illustrated. It is to be understood that this invention is not limited to the particular examples, process steps, and materials disclosed herein as such process steps and materials may vary somewhat. It is also understood that the terminology used herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the present invention will be limited to only the appended claims and equivalents thereof.