Abstract:
A catheter for the treatment of tissue, particularly for the treatment of cardiac tissue to alleviate cardiac arrhythmias includes a connector having mechanical use limiter that may be placed in the handle of the catheter or at any point along the electrical connection pathway to an electro-anatomic mapping system and/or ablation system. The mechanical use limiter has a counter wheel and locking pin which when engaged disables the reconnection of the connector to any mated connector after a predetermined number of uses.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a catheter for the treatment of human tissue, particularly cardiac tissue and more particularly cardiac arrhythmias, including atrial fibrillation. Such electrophysiology catheters have control handles which contain important circuitry related to their use and the connectors which connect the circuitry to electro anatomic mapping systems and/or radio-frequency (RF) generators. The present invention concerns a connector for such a catheter or other similar devices that limits the use or reuse of the catheter or other devices to a predetermined number of uses. 
     BACKGROUND OF INVENTION 
     Cardiac arrhythmias, atrial fibrillation in particular, persist as common and dangerous medical ailments, especially in the aging population. In patients with normal sinus rhythm, the heart, which is comprised of atrial, ventricular, and excitatory conduction tissue, is electrically excited to beat in a synchronous, patterned fashion. In patients with cardiac arrythmias, abnormal regions of cardiac tissue do not follow the synchronous beating cycle associated with normally conductive tissue as in patients with normal sinus rhythm. Instead, the abnormal regions of cardiac tissue aberrantly conduct to adjacent tissue, thereby disrupting the cardiac cycle into an asynchronous cardiac rhythm. Such abnormal conduction has been previously known to occur at various regions of the heart, such as, for example, in the region of the sino-atrial (SA) node, along the conduction pathways of the atrioventricular (AV) node and the Bundle of His, or in the cardiac muscle tissue forming the walls of the ventricular and atrial cardiac chambers. 
     Cardiac arrhythmias, including atrial arrhythmias, may be of a multiwavelet reentrant type, characterized by multiple asynchronous loops of electrical impulses that are scattered about the atrial chamber and are often self propagating. Alternatively, or in addition to the multiwavelet reentrant type, cardiac arrhythmias may also have a focal origin, such as when an isolated region of tissue in an atrium fires autonomously in a rapid, repetitive fashion. Ventricular tachycardia (V-tach or VT) is a tachycardia, or fast heart rhythm that originates in one of the ventricles of the heart. This is a potentially life-threatening arrhythmia because it may lead to ventricular fibrillation and sudden death. 
     One type of arrhythmia, atrial fibrillation, occurs when the normal electrical impulses generated by the sinoatrial node are overwhelmed by disorganized electrical impulses that originate in the atria and pulmonary veins causing irregular impulses to be conducted to the ventricles. An irregular heartbeat results and may last from minutes to weeks, or even years. Atrial fibrillation (AF) is often a chronic condition that leads to a small increase in the risk of death often due to strokes. Risk increases with age. Approximately 8% of people over 80 having some amount of AF. Atrial fibrillation is often asymptomatic and is not in itself generally life-threatening, but it may result in palpatations, weakness, fainting, chest pain and congestive heart failure. Stroke risk increases during AF because blood may pool and form clots in the poorly contracting atria and the left atrial appendage. The first line of treatment for AF is medication that either slows the heart rate or revert the heart rhythm back to normal. Additionally, persons with AF are often given anticoagulants to protect them from the risk of stroke. The use of such anticoagulants comes with its own risk of internal bleeding. In some patients, medication is not sufficient and their AF is deemed to be drug-refractory, i.e., untreatable with standard pharmacological interventions. Synchronized electrical cardioversion may also be used to convert AF to a normal heart rhythm. Alternatively, AF patients are treated by catheter ablation. Such ablation is not successful in all patients, however. Thus, there is a need to have an alternative treatment for such patients. Surgical ablation is one option but also has additional risks traditionally associated with surgery. 
     Diagnosis and treatment of cardiac arrhythmias include mapping the electrical properties of heart tissue, especially the endocardium and the heart volume, and selectively ablating cardiac tissue by application of energy. Such ablation can cease or modify the propagation of unwanted electrical signals from one portion of the heart to another. The ablation process destroys the unwanted electrical pathways by formation of non-conducting lesions. Various energy delivery modalities have been disclosed for forming lesions, and include use of microwave, laser and more commonly, radiofrequency energies to create conduction blocks along the cardiac tissue wall. In a two-step procedure—mapping followed by ablation—electrical activity at points within the heart is typically sensed and measured by advancing a catheter containing one or more electrical sensors (or electrodes) into the heart, and acquiring data at a multiplicity of points. These data are then utilized to select the endocardial target areas at which ablation is to be performed. 
     Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. In use, the electrode catheter is inserted into a major vein or artery, e.g., femoral artery, and then guided into the chamber of the heart of concern. A typical ablation procedure involves the insertion of a catheter having a tip electrode at its distal end into a heart chamber. A reference electrode is provided, generally taped to the skin of the patient or by means of a second catheter that is positioned in or near the heart. RF (radio frequency) current is applied to the tip electrode of the ablating catheter, and current flows through the media that surrounds it, i.e., blood and tissue, toward the reference electrode. The distribution of current depends on the amount of electrode surface in contact with the tissue as compared to blood, which has a higher conductivity than the tissue. Heating of the tissue occurs due to its electrical resistance. The tissue is heated sufficiently to cause cellular destruction in the cardiac tissue resulting in formation of a lesion within the cardiac tissue which is electrically non-conductive. 
     Electrophysiology catheters used in mapping and ablation procedures are often connected to electroanatomic mapping systems such as the Carto 3® system from Biosense Webster, Inc. Electroanatomic mapping systems are used in conjunction with mapping catheters to determine the anatomy of the endocardial tissue in the heart and where nerve fibers, nodes and bundles appear on that tissue which may be ablated to treat the aforementioned cardiac arrhythmias. 
     The handles of electrophysiology catheters for the mapping and ablation of cardiac tissue contain electronic circuitry which converts signals from the tip or ring electrodes near the distal end of the catheter into digital signals that can be communicated to such electroanatomic mapping systems (such as the Carto 3® system from Biosense Webster) and/or an RF generator/ablation system. An electrical connection between the handle and such systems is necessary. This electrical connection is usually accomplished by a “male/female” pin-socket connector such as a Redel™ type connector or other such connector. 
     Primarily, these types of catheters are sold as single use only devices due to concerns with the ability to properly clean and sterilize the devices for reuse in addition to concerns that certain location sensors or other electronic circuitry in the devices may be damaged during reprocessing and make such devices less reliable in subsequent reuses. Thus, there have been various patents issued concerning the use of electrical counters, etc that can control the use and reuse of such catheters. For example, U.S. Pat. No. 5,383,374 discusses the use of an catheter identification system that generates a signal related to the use or reuse of the catheter. Such systems are complicated to implement. 
     U.S. patent application Ser. No. 2006/0025651 relates to a connector assembly for the transfer of fluids having a first connector element pertaining to a reservoir and a second connector element pertaining to a medical dosage device which cooperate to give an irreversible connection between the two elements. The first and second elements cooperate with each other by clipping on a single translational movement of a connector element relative to the other to produce the irreversible connection so that at least one of the connection elements has elements to render the same breakable. 
     U.S. Pat. No. 6,394,983 to Mayoral discloses a cap and luer connector arrangement in which the luer connector sealing lip and seal region are distorted when the sealing lip is received into the crevice during initial screwed-on installation of the cap to the luer connector, forming an external seal. The sealing lip and seal region are heat set during autoclave-sterilization of the cap and luer connector arrangement, which prevents reinstallation of the cap once removed. 
     U.S. Pat. No. 5,989,240 to Strowe discloses an adapter for attaching a fluid handling device to a catheter including a seat to receive the catheter and a cavity distal to the catheter seat. The adapter further includes a retainer, a rotatable collar disposed over the retainer on the proximal end of the body, with an open port therethrough that is substantially aligned with the passageway to allow placement of the catheter into the passageway. The prevention of returning collar to a first position serves to substantially prevent the adapter from again being mounted onto a catheter and actively substantially prevents reuse of the adapter of the invention. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a mechanical use limiter particularly for use with an electrophysiology ablation and/or mapping catheter having a means for prohibiting the connection of the catheter to an electroanatomic mapping system or ablation system after a predetermined number of uses. 
     The present invention is also directed to a connector for establishing a mechanical and electrical connection between a medical probe and a system wherein the connector is adapted to connect to a mated connector and includes a mechanical limiter comprising a counter pin movably attached within the connector wherein the counter pin moves when the connector is mated to any mated connector. The mechanical limiter also includes a first rotatable gear having a notch rotated each time the counter pin is moved upon mating the connector to any mated connector and a limiter pin which is biased against the rotatable gear until the notch and limiter pin are aligned wherein the limiter pin moves into a locking position in the connector to block reconnection of the connector to any mated connector thereby blocking connection of the probe to the system. 
     The connector may also include a second rotatable gear that translates the longitudinal displacement of the counter pin into rotation for rotatable movement of the first rotatable gear. The limiter pin may contain barbs that engage upon movement of the limited pin into a locking position to prevent the movement of the limiter pin. The limiter pin may be comprised of a material which prevents physical alteration of the limiter pin. The mechanical use limiter may be housed in a handle of the medical probe or be placed at any point along the electrical connection between the probe and the system. 
     The mechanical use limiter may be used in an electrophysiology catheter having a handle and at least one electrode for use with an electrophysiology mapping and ablation system. The connector for connecting the catheter to the system is designed to mate with a mated connector in communication with the system and includes a mechanical limiter capable of blocking reconnection of the connector to any mated connector portion thereby blocking connection of the catheter to the system after a predetermined number of uses. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a schematic, pictorial illustration of an electrophysiology system for use with a catheter having a mechanical limiter in accordance with an embodiment of the present invention; 
         FIG. 2  is an elevational view of an embodiment of a bi-directional electrophysiology catheter having a mechanical limiter in accordance with the present invention. 
         FIG. 3  is a perspective view of the elements of a mechanical limiter in accordance with the present invention. 
         FIG. 4  is an exploded perspective view of the elements of a mechanical limiter in accordance with the present invention. 
         FIG. 5  is a perspective view of the limiter pin for use in a mechanical limiter in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Many diagnostic and therapeutic procedures, such as cardiac ablation and intracardiac electoanatomic mapping, use a minimally invasive probe, such as a catheter, which has at least one electrode mounted on its distal tip. The electrode is typically operated when the probe is pressed against a body cavity surface, such as the endocardium in the treatment of cardiac arrhythmias.  FIG. 1  is an illustration of a medical system  20  that connects with a catheter having a mechanical limiter in accordance with an embodiment of the present invention. System  20 , particularly control console  24 , may be based, for example, on the Carto™ systems produced by Biosense Webster, Inc. of Diamond Bar, Calif. System  20  comprises a probe  22 , such as an EP ablation or mapping catheter, and a control console  24 . In the embodiment described herein, it is assumed that probe  22  is used for diagnostic or therapeutic treatment, such as for mapping electrical potentials in a heart  26  or for performing ablation of endocardial or other tissue of heart  26 . However, such a probe  22  may have other uses in the heart or other organs or vasculature of a patient. 
     An operator  28 , such as a cardiologist, electrophysiologist or interventional radiologist inserts probe  22  through the vascular system of a patient  30  so that a distal end  32  of probe  22  enters a chamber of heart  26  (or other body cavity or vasculature). Operator  28  advances probe  22  so that the distal tip  34  of probe  22  engages endocardial tissue at a desired location or locations. Probe  22  is typically connected by a suitable connector at its proximal end to console  24 . 
     Console  24  typically uses magnetic location sensing to determine location coordinates of distal end  32  inside heart  26 . For this purpose, a driver circuit  36  in console  24  drives magnetic field generators  39  to generate magnetic fields within the body of patient  30 . Typically, the field generators  39  comprise coils, which are placed below the patient&#39;s torso at known locations external to the patient  30 . These coils generate magnetic fields in a predefined working volume that contains heart  26 . A magnetic field sensor  62  within distal end  32  of probe  22  (shown in  FIG. 2 ) generates electrical signals in response to these magnetic fields. A signal processor  49  processes these signals in order to determine the location coordinates of the distal end, typically including both location (x,y,z) and orientation (roll, pitch, yaw) coordinates. This method of location sensing is implemented in the above-mentioned CARTO system and is described in detail in U.S. Pat. Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612 and 6,332,089, in PCT Patent Publication WO 96/05768, and in U.S. Patent Application Publications 2002/0065455 A1, 2003/0120150 A1 and 2004/0068178 A1, whose disclosures are all incorporated herein by reference. 
     Signal processor  49  typically comprises a general-purpose computer, with suitable front end and interface circuits for receiving signals from probe  22  and controlling the other components of console  24 . The processor  49  may be programmed in software to carry out the functions that are described herein. The software may be downloaded to console  24  in electronic form, over a network, for example, or it may be provided on tangible media, such as optical, magnetic or electronic memory media. Alternatively, some or all of the functions of processor  49  may be carried out by dedicated or programmable digital hardware components. Based on the signals received from the probe  22  and other components of system  20 , processor  49  drives a display  44  to give operator  28  visual feedback through image  46  regarding the location of distal end  32  in the patient&#39;s body, as well as status information and guidance regarding the procedure that is in progress. Probe  22  is connected to system  20  through a cable  52 . Cable  52  contains electrically conductive wires necessary to connect the electrodes and/or magnetic field sensors to system  20 . Cable  52  also comprises a connector (usually male) which is mated to a connector  60  (shown in  FIGS. 2-4 ) in the handle of probe  22  for making a mechanical and electrical connection to the probe  22 . 
     Alternatively or additionally, system  20  may comprise an automated mechanism for maneuvering and operating probe  22  within the body of patient  30 . Such mechanisms are typically capable of controlling both the longitudinal motion (advance/retract) of the catheter and transverse motion (deflection/steering) of the distal end of the catheter. Some mechanisms of this sort use DC magnetic fields for this purpose, for example. In such embodiments, processor  49  generates a control input for controlling the motion of the catheter based on the signals provided by the magnetic field sensor in the catheter. These signals are indicative of both the location of the distal end of the catheter and of force exerted on the distal end, as explained further hereinbelow. 
     Processor  49  stores data representing image  46  in a memory  48 . In some embodiments, operator  28  can manipulate image  46  using one or more input devices  50 . Although  FIG. 1  shows a particular system configuration, other system configurations can also be employed to implement embodiments of the present invention, and are this considered to be within the spirit and the scope of this invention. For example, the methods described hereinbelow may be applied using location transducers of the types other than the magnetic field sensor described above, such as impedance based or ultrasonic location sensors. The term “location transducer” as used herein refers to an element mounted on probe  22  which causes console  24  to receive signals indicative of the coordinates of the element. The locations transducer may comprise a receiver on the probe that generates a location signal to the control unit based on the energy received by the transducer or it may comprise a transmitter, emitting energy that is sensed by a receiver external to the probe. Furthermore, the methods described hereinbelow may similarly be applied to therapeutic and diagnostic applications using not only catheters, but also other types of probes in the heart as well as in other organs and vasculature in the human body. 
     System  20  may be used with a probe  22  such as steerable bidirectional electrode catheter shown in  FIG. 2 . In  FIG. 2 , the catheter or probe  22  comprises an elongated catheter body  12  having proximal end  31  and distal end  32 , a tip section  34  with tip electrode  38  at the distal end of the catheter body  12 , and a control handle  16  at the proximal end of the catheter body  12 . The catheter body  12  comprises an elongated tubular member having a single axial or central lumen (not shown). The catheter body  12  is flexible, i.e., bendable, but substantially non-compressible along its length. The catheter body  12  can be of any suitable construction and made of any suitable material. A presently preferred construction comprises an outer wall made of polyurethane or PEBAX. The outer wall preferably comprises an imbedded braided mesh of stainless steel or the like to increase torsional stiffness of the catheter body  12  so that when the control handle  16  is rotated the tip section  34  will rotate in a corresponding manner. 
     The overall length and diameter of the probe or catheter  22  may vary according to the application. A presently preferred catheter  22  has an overall length of about 48 inches. The outer diameter of the catheter body  12  is not critical, but is preferably no more than about 8 french. In the depicted embodiment, the distal end of the tip section  14  carries a tip electrode  38 . Also mounted along the length of the tip section  34  is a ring electrode  40 . The length of the ring electrode  40  is not critical, but is preferably about 1 mm to about 3 mm. Additional ring electrodes can be provided if desired. If multiple ring electrodes are used, they are spaced apart in any fashion as desired so long as their edges do not touch. 
     The tip electrode  38  and ring electrode  40  are each connected to separate lead wires. Each lead wires (not shown) which extend through a lumen in the distal end  32  through the central lumen in the catheter body  12  and into the control handle  16  where it is connected to electronic circuit board (not shown). Electronic circuit board is connected to an appropriate connector  60 , which is adapted to mate to a mated connector on cable  52  so that catheter  22  can be plugged into or otherwise connected to a suitable monitor, source of energy, etc. Alternatively, the lead wires to tip electrode  38  and ring electrode  40  as well as any location sensors in the tip  14  of the catheter  22  may be connected directly to a connector  60  which is then plugged into or otherwise operably connected to a suitable monitor, source of energy etc. The lead wires are connected to the tip electrode  38  and ring electrode  40  by any conventional technique such as solder or the like. 
       FIGS. 3 and 4  depict the mechanical use limiter of the present invention. A male connector on cable  52  (not shown) preferably having a plurality of pins is used to make an electrical and mechanical contact with the mating female connector  60  in the handle  16  of probe  22 . Female connector  60  comprises a housing  72 , a plurality of electrical connectors  76  and a counter pin  80  biased by counter spring  81 . Electrical connectors  76  are connected to one or more wires (not shown) that are then either connected to the printed circuit board in handle  16  or directly to the electrodes  38  and  40  and location sensors in the tip of the probe. The male connector has at least one pin or prong which is capable of engaging the counter pin  80  thereby causing counter pin  80  to move. After the counter pin  80  is engaged it is pressed against a tooth of first gear  82  which causes first gear  82  to turn counterclockwise thereby translating the longitudinal motion of counter pin  80  into rotational movement. First gear  82  is mounted to mounting tube  86  using mounting screw  83  which engages threads in mount  84  on the side of mounting tube  86 . Teeth of first gear  82  engage one or more teeth of second gear  90  which is then rotated around mounting tube  86 . Each time the female connector  60  is engaged with a male connector the counter pin is pressed against the first gear  82 . Thus, the rotational movement of first gear  82  and second gear  90  can be pre-determined to be equivalent to a certain number of engagements or “uses” of the device being interconnected. Depending on this movement and the starting position of second gear  90  and the location of notch  91  a certain number of “uses” can be predetermined and mechanically programmed into the limiter. 
     After a successive number of interactions between the male and female connectors, counter pin  80 , first gear  82  and second gear  90 , notch  91  in second gear  90  is aligned with limiter pin  92 . Once notch  91  is aligned with limiter pin  92 , limiter pin  92  is “fired” or biased by spring  93  so that limiter pin  92  pushes out of lumen  87  which is coaxial with mounting tube  86  through notch  91  and into lumen  73  in housing  72  of female connector  60 . Once male connector on cable  52  is removed, limiter pin  92  prohibits reconnection of the same or another male connector to female connector  60 . Barbed or hooked features on the limiter pin  92  prevent manipulation of the limiter pin  92 .  FIG. 5  shows a perspective view of one possible embodiment of limiter pin  92  having a plurality of barbs  102  along two prongs  104 . Limiter pin  92  also may be made of a material that would be difficult to cut or otherwise destroy without destroying the mechanical and electrical connectivity properties of female connector  60  such as stainless steel, titanium, high-carbon stainless steel and the like. Otherwise, the limiter pin  92  and the other components of the mechanical limiter can be made of polycarbonate or other known polymeric materials. 
     Alternatively, female connector  60  with the mechanical limiter of the present invention could be placed outside of handle  16  connected to handle  16  by a length of wire. Connector  60  does not need to be within handle  16  to have the same connection and use limitation functions. 
     The preceding description has been presented with reference to presently preferred embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention. 
     Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fair scope.