Source: https://patents.google.com/patent/EP3284518A1/en
Timestamp: 2019-09-18 11:53:53
Document Index: 636294992

Matched Legal Cases: ['art 102', 'art 102', 'art 102', 'art 102', 'art 102', 'art 102', 'art 102', 'art 102', 'art 102']

EP3284518A1 - Secondary header for an implantable medical device incorporating an iso df4 connector and connector cavity and/or an is4 connector and connector cavity - Google Patents
EP3284518A1
EP3284518A1 EP17193030.8A EP17193030A EP3284518A1 EP 3284518 A1 EP3284518 A1 EP 3284518A1 EP 17193030 A EP17193030 A EP 17193030A EP 3284518 A1 EP3284518 A1 EP 3284518A1
EP17193030.8A
2012-03-07 Application filed by Greatbatch Ltd filed Critical Greatbatch Ltd
2012-03-07 Priority to EP12158362.9A priority patent/EP2497532A3/en
2018-02-21 Publication of EP3284518A1 publication Critical patent/EP3284518A1/en
A secondary header for an active implantable medical device (AIMD) incorporates a secondary header plug configured for mating insertion into an AIMD ISO DF4 or IS4 connector cavity, a secondary header ISO DF4 or IS4 connector cavity, and at least one replacement lead connector cavity. The secondary header plug has four electrical contacts which correspond to four electrical contacts of the AIMD connector cavity. The secondary header connector cavity has less than four electrical contacts conductively coupled to the secondary header plug electrical contacts. The replacement lead connector cavity has at least one electrical contact conductively coupled to at least one electrical contact of the secondary header plug.
And even if all these issues were overcome another problem would remain. That is, the defective lead is still in place and connected to the pulse generator circuits. The sine qua none of ICD lead failure, in addition to failure of therapeutic pace-sense or defibrillation functions, which the new ICD pulse generator and lead can correct, is inappropriate and on occasion involves lethal low impedance and high intensity shocks in the 100s of volts range. By inappropriate it is indicated that the patient is shocked, often repeatedly, not because a life threatening arrhythmia has occurred but because the defibrillator sensing circuits are receiving high rate signals generated from sites of insulation failure and or from conductor fractures in the original ICD leads low voltage/pace sense components. Alternatively, if the failure had occurred in the high voltage components of the DF4 lead, the potential for short-circuiting of required life saving shocks would persist. Prior art abandoned lead components can also be problematic during MRI scans because they can pick up high-power RF induced energy which can lead to overheating of the lead and/or its distal electrode, which can heat up or even burn surrounding heart tissue.
Reference is made to U.S. Patents 7,225,034 and 7,242,987 , the contents of which are incorporated herein by reference. These patents describe a lead-based adaptor for use with DF4 pulse generators at the time of ICD and lead system initial implantation, when defibrillation thresholds indicate an inadequate safety margin. These adaptors are similar in design to prior art products in that a connector, in this case DF4, is disposed at one end and connects into an elongated insulated, lead body like segment containing 4 lead wires. This eventually bifurcates into two arms, one terminating in a DF-1 connector cavity and the other terminating in a DF4 connector cavity. This allows reuse of the DF4 lead and parallel hard wired cross connection of one or more of the high voltage outputs to one or more additional DF-1 leads to see if an improved shock vector can be obtained. The adaptors described in these patents introduce all of the previously described disadvantages and concerns related to adaptors in general but in addition will further greatly increase the bulk of a pectoral or other pocket. The '034 and '987 patents are not directed to a situation where a previously implanted lead conductor has failed. These patents are directed towards supplying additional connector cavities if additional defibrillation vectors are required and are not relevant to the post implant repair of a high voltage shocking coil or failed pace sense functions There is no provision within the '034 patent, for example, to disconnect defective lead component or components, and prevent them from interfering with sensitive AIMD circuitry and functions. FIG. 3 of the '987 patent does show a switch 110 which provides a means for reversibly decoupling the proximal high voltage electrode of the first DF4 lead from the high voltage electrode of the supplemental DF-1 lead, but this is neither permanent nor reliable, and introduction of a somewhat rigid switch component into the grip zone or lead like body of the adaptor would add complexity and focus flexural stresses with increased probability of fracture of adjacent conductors. The FIG. 3 drawing description of the '987 patent states that, "When defibrillation thresholds achieved using coil electrodes on a first lead, for example electrodes 54 and 52 of said lead 40 shown in FIG. 1, are unacceptably high such that placement of a second high-voltage lead, for example, lead 60, is required, it may be desirable to provide a high-voltage signal to the second lead without providing the same high-voltage signal to a coil electrode on the first lead. As such, switch 110 is provided between connector ring 28 and conductor 78A or anywhere along conductor 78A, which is coupled to contact 86 as shown previously in FIG. 2." In other words, the switch of the '987 patent is directed towards optimizing therapeutic defibrillation vectors. As used in the '987 patent, the word signal refers to a high-voltage biphasic or monophasic defibrillation shock. Nowhere in the '034 or '987 patents is the problem of a previously implanted damaged or defective lead conductor or other component addressed, nor is provision made to provide a header adaptor to be able to cope with this. And, as with all prior art adaptors, such as from Oscor, or Medtronic such as described in the '034 and '987 patents, are lead based. This means that the bifurcated connector cavity terminals for receiving the bulky DF4 connector and the added DF-1 lead connector are located several centimeters along a lead away from the pulse generator. Accordingly, the pectoral or alternative site, pocket bulk is increased and all the other lead based adaptor disadvantages are preserved. In addition, the '987 and '034 patents lead-based adaptors have all of the same problems as previously described for prior art leads with trifurcated lead connectors wherein, subsequent surgery and removal of the device can be problematic. One may also go to the website of Oscor Incorporated to see an entire family of lead-based adaptors.
As previously stated, lead conductors can fail for a variety of reasons. Conductor failures and recalls of implanted leads have been common in the implantable medical device industry. An interesting exercise is to do a simple Google search using the following key words: "pacemaker lead recalls." Literally, hundreds of "hits" come up. It has been common in the implantable medical device industry to abandon a defective lead and simply implant a new one roughly in parallel with it through the venous system.
In a preferred form of the invention, a secondary header for an active implantable medical device (AIMD) incorporating an ISO DF4 or IS4 connector cavity having four electrical contacts is provided. As used herein, the ISO standard refers to American National Standard ANSI/AAMI/ISO 27186:2010, entitled, "Active Implantable Medical Devices - 4-Pole Connector System for Implantable Cardiac Rhythm Management Devices - Dimensional and Test Requirements". The secondary header comprises (1) a secondary header plug configured for mating physical and electrical insertion into the AIMD ISO DF4 or IS4 connector cavity, the secondary header plug having four electrical contacts which correspond to the four electrical contacts of the AIMD ISO DF4 or IS4 connector cavity, (2) a secondary header ISO DF4 or IS4 connector cavity having less than four electrical contacts conductively coupled to the secondary header plug electrical contacts, and (3) at least one replacement lead connector cavity having at least one electrical contact conductively coupled to at least one electrical contact of the secondary header plug.
Reference is made to section 3 of ISO Standard 27186 as providing definitions to terms and terminology which are used to describe the present invention. Accordingly, as used herein: "bipolar" means having two poles or electrodes; "connector system" refers to an assembly consisting of a lead connector and a connector cavity that are electrically and mechanically joined; "connector cavity" is defined as a cavity within the pulse generator which is intended to receive a lead connector and an identical cavity within a secondary header; "fixation zone" is a zone located in the lead connector pin and within the connector cavity where the lead connector is mechanically secured within the connector cavity; "high-voltage" is defined as electrical potentials greater than 20 volts up to 1000 volts (Note: High-voltages are generally used for defibrillating the heart); "lead connector" or "plug" is the part of the lead that is intended for insertion into the connector cavity of a pulse generator; "lead connector contacts" are defined as conductive elements on the lead connector which include the lead connector pin and lead connector rings; "lead connector pin" is defined as the most proximal conductive element of a lead connector provided for making electrical contact as well as for securing the lead connector within the connector cavity; "lead connector ring" defines angular conductive elements on the lead connector intended for making electrical contact within the connector cavity (Note: the 4-pole connector (DF4 or IS4) has up to 3 lead connector rings and a lead connector pin); "lead electrode" is the distal part of a lead through which electrical impulses are transmitted to or from cardiac tissue (Note: high-voltage electrodes are capable of delivering high-voltage electrical impulses; Low-voltage electrodes are used for transmitting and sensing low-voltage impulses and are generally not suitable for delivering high-voltage); "low-voltage" defines electrical potentials less than or equal to 20 volts; "pulse generator" is any type of active implantable medical device (AIMD) and particularly those devices that delivery electrical energy to effect cardiac rhythms; "securing mechanism" is defined as a mechanism within the connector cavity intended for mechanically securing the lead connector (Note: a securing mechanism can be an active mechanism, such as a set screw or it can be a passive mechanism, such as a self-engaging latch. It can also serve a second function of providing electrical contact with the lead connector, as is the case with a set screw); "tripolar" means having three poles or electrodes.
Furthermore, as used herein the term "lead" refers to an implantable lead which has a lead body and one or more conductors. "Lead conductor" refers to one or more coiled or filer wires which are located within the lead body. Lead conductors are generally insulated from each other. The term "leadwire" refers to internal wires or circuit traces within the secondary header of the present invention. Leadwires may also refer to wires or circuit traces that are located entirely inside of the AIMD hermetically sealed housing.
FIG. 2 shows a prior art outline diagram of the human heart 102 and a cardiac pacemaker 100A. Shown are two implanted leads 104 and 106 which both have IS-1 connectors 104a, 106a at their proximal ends. Lead 104 is routed transvenously into the right atrium (RA) 108 of the heart 102. Lead 104 is a bipolar lead, meaning that it has two conductors. One of the lead conductors terminates in the distal tip electrode 104b and the other conductor terminates in the distal ring electrode 104c. Implanted lead 106 is routed into the right ventricular cavity (RV) 110. It is also bipolar, meaning that it has two conductors, one of which is connected to the distal tip electrode 106b and the other conductor is connected to the distal ring electrode 106c. This is known in the art as a dual chamber bipolar pacemaker 100A. The pacemaker 100A has a metallic housing 112 generally of titanium, stainless steel or the like. It also has a header block 114 which holds connector assembly components in accordance with ISO Standard IS-1. In this case, the header 114 has two connector cavities 116 and 118 into which the IS-1 lead proximal connectors 104a, 106a can be inserted. Generally, there would be set screws to fix the connector ring and pin electrodes firmly in place (not shown). There are leadwires 120, 120', 122, 122' routed from the connector cavities 116, 118. These four leadwires 120, 120', 122, 122' are routed to a hermetic seal 124 where the wires pass through the housing 112 in non-conductive relation. It is very important that the housing 112 of the AIMD be completely hermetic to protect sensitive electronic components, for example, those that are shown on circuit board 126.
FIG. 3 also shows a prior art outline drawing of a human heart 102 and in this case, the device 100B is a dual chamber implantable cardioverter defibrillator. One can see that there are four connector cavities 116, 116', 118, 118' into which the IS-1, DF-1, IS-1 and DF-1 proximal connectors 104a, 104a', 106a, 106a' may be inserted. Again, there are two implanted leads 104 and 106. Bipolar lead 104 is transvenously inserted into the right atrium 108 of the heart 102. It has a distal tip electrode 104b and a distal ring electrode 104c. Lead 106 has four conductors. Two of these conductors route to the distal tip electrode 106b and the distal ring electrode 106c. The DF-1 connectors 104a', 106a' are high-voltage conductors. One of the high-voltage connectors 104a' is routed to shocking coil (HP) 128, which is generally located in the superior vena cava (SVC) 130 of the heart 102. The second high-voltage shocking coil (HD) 132 is located in the right ventricle 110. In total, there are 6 lead conductors in the system, as shown in FIG. 3.
In FIG. 3, one can see that there is a trifurcated lead adaptor 134 which combines the connectors 104a', 106a, 106a' for the two high-voltage shocking coils 128, 132 along with one low-voltage tip 106b and ring 106c circuit. In the prior art, excess lead is typically wound up in the pectoral pocket, either adjacent to or around the pacemaker. The trifurcated adaptor 134 and lead system 104, 106, as shown in FIG. 3, makes for a very bulky pectoral pocket lead arrangement as compared to the arrangement shown in Fig. 2. In addition the four separate connectors and associated proximal lead segments tend to create crisscrossing tissue ingrowth paths. When the ICD 100B needs to be replaced for approaching battery end of life or any other indication, this tangle of insulated conductor segments all tend to have tissue in-growth which makes the surgery difficult as all of these leads must be carefully excised and separated.
FIG. 4 is another prior art cross-section of the human heart 102 again with a dual chamber ICD 100B. As illustrated in FIG. 3, the dual chamber ICD 100B has both pacing and high-voltage shocking functions. The electrode placements, both for the high-voltage shocking coils and also the low voltage pace and sense circuits are the same as previously described for FIG. 3. However, in FIG. 4, the defibrillator 100B lead 106 incorporates the new state-of-the-art inline quadripolar DF4 proximal lead connector 106a" as shown. In this case, there are now only two connector cavities 116 and 118" in the defibrillator 100B header 114. Connector cavity 116 is a low-voltage connector cavity for receipt of the IS-1 proximal connector 104a. Connector cavity 118" is a DF4 quadripolar connector cavity designed to receive the DF4 proximal connector 106a". In this case, there are still two leads 104 and 106 that are routed down into the various chambers of the heart as previously described in FIG. 3. When one considers that excess lead is wound up in the pacemaker pocket, one can see that the configuration in FIG. 4 is vastly superior to the trifurcated connector 134 as previously illustrated in FIG. 3. The surgical implant procedure is considerably simplified and there is a lot less bulk created in the pacemaker pocket which increases both reliability and patient comfort.
FIG. 5 is a prior art drawing of a human heart 102 and ICD 100B that is state-of-the-art. This defibrillator system not only has high-voltage shocking and low-voltage pacing functions, but it also has cardiac resynchronization therapy (CRT) capabilities through electrodes placed transvenously into the right atrium 108 and then through the coronary sinus 138 into epicardial veins 140, 142 on the surface of the left ventricle (LV) 136. In this case, there are two types of quadripolar connectors being used at the proximal lead ends. There are three implanted leads 104, 104''' and 106". Lead 104 is a low-voltage lead which is routed to distal tip 104b and ring 104c electrodes in the right atrial appendage 108'. Lead 106" is a quadripolar low-voltage/high-voltage lead. Lead 106" contains four conductors, two of which are connected to high-voltage shocking coils 128 and 132. There are also two low-voltage conductors in lead 106" which are routed to the distal tip electrode 106b and distal ring electrode 106c in the right ventricular apex 110'. The third lead 104a is a four-conductor IS4 or quadripolar lead which is routed transvenously through the coronary sinus 138, the great cardiac vein 140 and into a branch vessel 142 which is part of the epicardial or surface venous system draining blood from the left ventricle 136 back into the right atrium 108. Shown are four electrodes 144a through 144d. The IS4 proximal connector for lead 104''' is plugged into connector cavity 116''' on the header block 114 of the ICD 100B. The DF4 connector 106" is plugged into connector cavity 118" and the IS-1 proximal connector 104 is plugged into connector cavity 116 as shown.
Referring once again to FIGS. 4 and 5, it is obvious that the use of in-line quadripolar connectors greatly reduces the number of required connectors. As previously mentioned, there are a number of major advantages associated with this in addition to less bulk in the device tissue pocket. However, there is no provision in the DF4 or IS4 Standards for what remedial steps to take if one of the lead conductors or other components fails or becomes inoperable or is dysfunctional. For those experienced in the implantable medical device business, they realize that the implanted lead is almost always the weak point in the system. In other words, it is not uncommon for lead conductors, insulation, and fixation mechanisms to fail in a variety of ways. Since 1980, there have been a continual series of lead recalls, including the 2007 recall of all the Medtronic Sprint Fidelis models, and the more recent recall of some St. Jude's ICD lead models. Average failure rates of some quadripolar ICD lead models, approaching 25% after implantation in female patients for 5 years, and of over 15% in male patients, have been independently documented in a recent multi-center publication in the leading journal Circulation. And failure rates were even higher if the popular subclavian or particularly an axillary vein access route was chosen. These recalls are not only financially damaging for the industry and the companies involved, but are also devastating for the patients who have to go through additional surgeries to replace defective leads. In addition they place great stress on healthcare delivery systems, physicians, and hospital and clinic staff members etc. In short, as time goes on and the DF4 and IS4 quadripolar connector leads become more popular, it is unavoidable that some degree of lead conductor or component failures or dysfunction requiring repair will occur. While it is hoped that these failures will be at a much lower rate than in the recent recalls, there is no guarantee, as independent reports comparing the ICD lead products of the major manufacturers indicate a minimum failure rate of even less complex tripolar products in the range of 8 to 10% by 10 years (Circ Arrhythmia Electrophysiol. 2009; 2:411-416). It is still important therefore to consider what will happen when a patient with a DF4 or IS4 lead failure or malfunction presents. Referring to FIG. 5, for example, let's say there was a failure in the DF4 lead 106" wherein, there was a defect in the conductor or electrode 106b, 106c. This could mean that there was a fracture in the lead conductor or that the distal electrode 106b became dislodged or even that there was an increase in what's known as pacing capture threshold (PCT) or an insulation breach. In any event, loss of proper pacing and/or biologic signal sensing capabilities involving electrode 106b can cause a catastrophic clinical outcome for a patient depending on the system as shown in FIG. 5. In fact, if the patient was continuously pacemaker dependent, the loss of pacing function would be immediately life-threatening. If the physician is presented with such a case wherein for example, one of the four conductors in lead 106" has failed, there are currently no good choices. Explanting lead 106" will be difficult since tissue in-growth tends to tie all three leads together. Even using a laser sheath to try to vaporize the non-calcified adhesions is not always successful, involves risks to the patient and to the maintenance of position and function of the still functional 104 and 104''' leads. One choice would be to remove the defibrillator 100B and replace it with a special four-connector cavity defibrillator. In this case, an additional low-voltage connector cavity would be provided so that an additional low-voltage lead could be implanted into the right ventricle. The low-voltage tip electrode 106b and ring electrode 106c and their associated lead conductors would be abandoned and left in place. A new low-voltage lead would be transvenously inserted down into the right ventricle 110 into a location that provided for proper pacing capture and sensing. Thus, the patient would gain an additional relatively small diameter lead which typically would not present any major physiologic problems. While this presents a way to implant an extra lead to make up for the failed conductor or component in lead 106", it comes at great expense (at least $20,000 for the replacement custom header defibrillator) plus the waste of the standard ICD that has to be explanted and discarded.
FIG. 6 is an enlarged pictorial view of an embodiment of a proximal end portion of a DF4 high-voltage connector 146. As can be seen, at its proximal tip, it has a low-voltage pin electrode connection contact 148a and it also has a ring low-voltage connection 148b next in line. In addition, it has two high-voltage ring connection contacts 148c and 148d. This makes for a four-conductor lead as previously described as lead 106a" in FIGS. 4 and 5. This is the same as the DF4 lead 106" previously shown in FIG. 5.
FIG. 7 is a blown-up pictorial view of an embodiment of a proximal end portion of a IS4 low-voltage quadripolar lead connector 150. As illustrated, the connector 150 comprises a low-voltage connector tip 152a and three low-voltage electrode connection contacts 152b, 152c and 152d. This is the same as the low-voltage IS4 left ventricular lead 104''' as previously described in FIG. 5.
FIG. 10A shows a dual chamber defibrillator 100B primary header 114 with the addition of CRT functions requiring a total of five connector cavities. The two high-voltage (HV) connector cavities 118a, 118b are DF-1 and the low voltage connector cavities (RV) 116a, (A) 116b and (LV) 116c are IS-1 connectors. Required leads and intended functions are identical to what is described in detail above. The additional, fifth low-voltage connector cavity is for receipt of an IS-1 type connector, whereby, a fifth lead would be routed through the venous system into the right atrium 108, the coronary sinus 138 and from there into subepicardial branch coronary veins near the lateral surface of the left ventricle, (see LV 136 in FIG 5).
FIG. 14 is a sectional view taken generally from section 14-14 from FIG. 13 showing the top of the AIMD 100A header 114 and a cross section of the low profile secondary header 160, including the interiors of the secondary header's, DF4 172 and in this case DF-1174 connector cavities.
FIG. 22 is an end view taken from FIG. 21 illustrating that the low profile secondary header 160 and its connector cavities 172 and 174 conform and fit tightly to the AIMD 100 header 114 and housing 112. In this case, the AIMD 100 is a dual chamber, plus resynchronization cardioverter defibrillator as in FIG 10B.
FIG. 24 shows an AIMD 100,100B with lead connections into the outlined drawing of a human heart 102. FIG. 24 illustrates a DF4 compatible ICD and leads 106", 104 that had been previously implanted. During initial implant, and prior to partial failure of lead 106" the low profile secondary header 160 was of course not present. In addition, the new IS-1 lead 180 was also not present. In the pre-existing configuration, there was an IS-1 pace sense lead 104 plugged into the atrial connector cavity 116b of the device header 114. The existing DF4 proximal lead connector 106a" was plugged directly into the DF4 connector cavity 118c of the device header 114. The pre-existing IS-1 lead 104 was routed from the device atrial connector cavity 116b intravenously into the right atrium 108. This IS-1 lead 104 has a distal tip electrode 104b and a distal ring electrode 104c. The four-conductor DF4 lead 106"was routed to a high-voltage shocking coil 128 in the superior vena cava 130 and to a second high-voltage shocking coil 132 located in the right ventricle 110. In addition, there were bipolar low-voltage conductors in lead 106" routed to a distal tip electrode 106b" and a distal ring electrode 106c", both of which were located in the right ventricular apex 110'. For this particular patient, at some point in time, there was a fracture or break 182 of the lead conductor 106" that connects to distal tip electrode 106b". In this example, a break or fracture is illustrated. However, there are many other conditions that can also result in the need for replacement of the low voltage pace sense functions of a DF4 lead. They would include insulation deterioration associated with low stimulation and or sensing resistance measurements at the time of patient presentation with symptoms or during routine clinic follow-up, poor pacing capture threshold, distal tip migration or micro perforation and the like. In this case, with a broken lead tip conductor 106b", the AIMD 100, 100B, which is a dual chamber ICD 100B with pacing functions, would no longer be able to pace the right ventricle. This condition can be life-threatening to a pacemaker dependent patient. In addition friction voltages generated by motion between the broken ends of the conductor can generate high frequency artifacts that the ICD must interpret as the life threatening abnormal heart rhythm ventricular fibrillation. Thus, at best, a patient may receive multiple painful shocks for no apparent reason. Further, many ICDs are currently implanted prophylactically and are never called upon to fire off their 100s of volt charges appropriately, but have still caused the death of their patient by unnecessary high voltage shocks thereby inducing the fatal arrhythmia the system was implanted to treat, but which the ICD 100B is then unable to correct.
Accordingly, rapid intervention by medical personnel is paramount. The low profile secondary header 160 of the present invention provides for a quick and simple solution. The patient's pectoral or other tissue pocket harboring the defective system is opened up so that the AIMD 100,100B is exposed. At this point, a new relatively small diameter lead 180 is inserted transvenously to a new location in the right ventricle 110, tested and repositioned as necessary until the best possible combination of pacing capture and sensing thresholds can be obtained. The new lead, 180 in FIG 24, is shown in one such possible location, with its distal tip electrode 180b and associated ring electrode 180c just up from the RV apex 110', on the septum between the right and left ventricles. It should be noted that it is neither practical nor possible to just replace only the tip electrode circuit of a bipolar cardiac pacing lead. This is because the tip electrode and ring electrode act as a system. The separation between the tip and ring electrodes is very important in order to properly sense cardiac activity while also minimizing detection of stray noise, such as electromagnetic interference in the patient environment, and the sensing of electrical activity in other heart chambers, in skeletal muscle etc. Accordingly, the replacement lead 180 is a bipolar lead having two conductors and appropriately closely spaced tip 180b and ring 180c electrodes. It is plugged into replacement connector cavity 174 of the low profile secondary header 160. The pre-existing DF4 lead 106" is then plugged into the connector cavity 172 of the secondary header 160.
FIG. 25 illustrates the human heart of FIG. 24 with all of the conductors in leads 106", 104 and 180 shown. The original and still functional lead 104 has two conductors 104d, one of which is routed to distal ring electrode 104c and the other conductor is routed to distal tip electrode 104b shown located in the right atrial appendage 108'. The original DF4 lead 106" has four conductors 106d". One of these conductors 106d" is routed to the high-voltage shocking coil 128 located in the superior vena cava 130. Another of these lead conductors 106d" is routed to a second high-voltage shocking coil 132 located in the right ventricle 110. The DF4 lead 106" also has bipolar low-voltage conductors 106e", one of which is routed to the distal ring electrode 106c" and another low-voltage conductor that was routed to distal tip electrode 106b". In this example, this conductor has fractured at location 182 such that the distal tip electrode 106b" is no longer in electrical contact with the AIMD 100, 100B electronic circuits. Also shown is the new lead 180 which is a bipolar IS-1 lead, which has two conductors 180d, one of which is routed to new distal ring electrode 180c and new distal tip electrode 180b. For simplicity, the low profile secondary header 160 and the device 100, 100B previously illustrated in FIG. 24 is not shown.
FIG. 26A shows the electrical connections for the low profile secondary header 160 from FIG. 24. It should be noted that in connector cavity 172, no electrical connections are made to the AIMD at contact points (LR) 184a and (LP) 184b. This disconnects the low-voltage functions LR and LP of the AIMD 100 from the DF4 secondary header connector cavity 172. It is very important to disconnect the LR and LP functions because the partially failed DF4 lead 106" to be reinserted into the low profile secondary header connector cavity 172 still has connections to distal ring electrode 160c", and also to the broken off portion 182 of the conductor that was previously routed to distal tip electrode 106b" in FIGS. 24 and 25, and can transmit a variety of inappropriate signals to confuse the pulse generator sensing circuits. It is very important that this noise not enter into AIMD circuitry where it could cause improper device function or false interpretation by AIMD software algorithms.
FIG. 27A is very similar to FIG. 26A except that in this case, there has been a failure of the lead conductor in lead 106" from FIG. 24, that is routed to the high-voltage shocking coil (HP) 128 that's located in the superior vena cava 130. In this case, contact 186a has been disconnected in the secondary header 160 connector cavity 172 so that no interference or short circuiting can affect the AIMD electronics. The selective deletion of electrical contacts has led us to denote the secondary header connector cavity 172 as DF4(-). However, DF4(-) should be considered generic for any secondary header DF4 like configuration with one or more electrode contact site disconnections. In accordance with the present invention, a secondary header 160 DF-1 lead replacement connector cavity 174 has been provided so that a new high-voltage shocking coil lead in accordance with the DF-1 Standard can be inserted transvenously and then plugged into the secondary header 160 replacement connector cavity 174. Contact (HP) 198 in the replacement connector cavity 174 replaces contact (HP) 186a in connector cavity 172 and is routed to contact ring 190a by leadwire 192a.
FIG. 29A presents a completely different situation. This illustrates a low profile secondary header 160 with an IS4 low-voltage quadripolar connector and two connector cavities, one IS-1 cavity 174 and one IS4(-) cavity 172. One is referred to lead 104''' in FIG. 5 to see how an IS4 lead 104''' is routed through the coronary sinus 138 and into an epicardial vein 140, 142 near the lateral surface of the left ventricle 136. In this particular example, in FIG. 29A, there has been a lead 104''' conductor failure such that the tip electrode 144d of FIG. 5, is no longer functional. Accordingly, as shown in FIG. 29A, there is no wire connection to tip LP 184b in the secondary header 160 IS4(-) connector cavity 172. This disconnection is important so that stray noise and short circuiting cannot affect AIMD circuitry, after all connections to the secondary header 160 and of the secondary header to the usually original AIMD 100, 100B, and reimplantation of the reconfigured system have been completed. As can be seen, leadwire 192a has been disconnected from point (LP) 184b in the IS4(-) connector cavity 172. Instead leadwire 192a has been rerouted to connection tip point (LP) 196 in IS-1 replacement connector cavity 174. This allows a new lead to be transvenously or transthoracically inserted into, or attached to, the left ventricle, and then plugged into this replacement connector cavity 174. As after the partial failure of a IS4 low voltage lead, the still functional components of the IS4 lead are reconnected by insertion of its IS4 connector into the IS4 (-) secondary header connector cavity 172. FIG. 29A demonstrates repair of an IS4 lead partial failure by using a new unipolar IS-1 lead plugged into replacement connector cavity 174. Any pair of the ring electrodes on plug 168 in FIG. 29A could also be disconnected from their respective electrodes in connection cavity 172, and repair accomplished using a bipolar IS-1 lead. FIGURE 29B is a line diagram showing which connections are active and inactive in connector cavities 172 and 174 from FIG. 29A.
FIG. 30B is very similar to FIG. 27A showing the same DF4(-) configuration in a low profile secondary header 160. Like in FIG. 27A, 30B presents a low profile secondary header 160 designed to correct a situation where there has been a failure of the lead conductor that is routed to the shocking coil (HP) 128 located in the superior vena cava 130. As in FIG. 27A, there is no leadwire connecting the electrical ring (HP) 186a from the connector cavity 172 to connector plug contact ring 190a. However, there is a major difference from FIG. 27A illustrated in FIG. 30B, as this abandoned conductor connection HP 186a is now electrically connected to the energy dissipating surface (EDS) 200 of FIG. 30A. This is very important considering the marked increase in the need for MRI diagnostic interventions in general, and particularly in the type of heart patient requiring AIMDs, as it has been shown that conductors in abandoned leads can pick up substantial RF energy from the MRI RF-pulsed field. One is referred to U. S. Patent Publication 2010/0324639 for a more thorough description of the problems associated with abandoned leads and how energy dissipating surfaces can alleviate overheating of such leads. One is also referred to U.S. Patent Publication 2010/0217262 , which also describes energy dissipating surfaces. Both of these patent publications are incorporated herein by reference.
FIG. 31 is a partial section view taken from section 31-31 from FIG. 30B. It shows that the energy dissipating surface 200 can be flush or even recessed into the generally smooth body of the low profile secondary header 160. To see how dangerous abandoned leads can be in an MRI environment, one is again referred to the article entitled, PACEMAKER LEAD TIP HEATING AND ABANDONED AND PACEMAKER-ATTACHED LEADS AT 1.5 TESLA MRI. Reference Journal of Magnetic Resonance Imaging 33:426-431 (2011). FIG. 2 of this paper shows that abandoned pacemaker leads that are capped (not connected to an AIMD) can heat as much as 31°C at the distal electrode over body temperature. This is an extremely dangerous condition that would cause damage to adjacent cardiac tissue. The low profile secondary headers 160 of the present invention, when they do not have an energy dissipating surface EDS, act very similar to an abandoned capped lead. In other words, when the proximal partially failed leads DF4 or IS4 connector is inserted into connector cavity 172 of the low profile secondary header 160, the lead contacts are then electrically insulated from coming into contact with body fluids or tissues. Accordingly, it is very important to provide an energy dissipating surface feature so that the RF energy that's picked up in the abandoned lead conductor can be harmlessly dissipated as energy diverted into the tissue surrounding the AIMD 100 pocket. It is also interesting to note why abandoned leads are more dangerous than a connected lead. This is because leads properly connected into a pulse generator header benefit from the prior art EMI filter feedthrough capacitors that are present at the point of primary header, connector wire ingress 124 into modern AIMDs. This filter capacitor presents a very low impedance at MRI RF frequencies thereby substantially connecting the lead conductor to the metallic housing 112 of the AIMD as in FIGs 2 through 5. In this case, the AIMD housing 112 acts as a very effective energy dissipating surface. The location and operation of these prior art feedthrough capacitors is more thoroughly described in U.S. Patents 4,424,551 ; 5,333,095 ; 5,905,627 ; and 6,765,780 . MLCC capacitors can also be very effective energy diverters as described in U.S. Patents 5,896,267 and 5,650,759 . All of the aforementioned patents are incorporated herein by reference.
FIG. 34 shows that the diverter element 204 of FIG. 32 can be a capacitor (C) 206. The frequency selective diverter element capacitor 206 has a capacitive reactance. As more thoroughly described in U.S. Patent Publication 2010/0324639 , the reactance, such as a capacitive reactance, can help to cancel a lead conductor source impedance which could be primarily inductive. In this way, maximal energy transfer can be accomplished from the abandoned implanted lead conductor to the energy dissipating surface 200. In other words, a short circuit 202, as illustrated in FIGS. 31 and 33, may not draw the maximal energy out of the lead.
FIG. 37 is very similar to FIG. 36 and shows a resistive element 208 in series with the inductor 210 and capacitor 206 of the L-C trap filter 212. This resistor element 208 is important to control the Q or 3-dB bandwidth of the resonant trap filter 212 and also can be tuned for maximal energy transfer to the energy dissipating surface 200. Again, one is referred to U.S. 2010/0324639 , the contents of which are incorporated herein by reference.
FIG. 39A is very similar to FIGS. 30A and 38A except that, in this case, the energy dissipating surface 200 is a ring located around the connector cavity 172. There could be a second or even optional ring 200' located around the entire housing of the low profile secondary header 160 as shown. These EDS rings 200, 200' can be of varying widths as required to dissipate sufficient RF energy during MRI scans. The rings 200, 200' can be round or oval as shown. Any shape can be used as long as it conforms tightly to the shape of the secondary header 160. In a preferred embodiment, they would be flush with the surfaces of low profile secondary header 160.
FIG. 40 is a low profile secondary header 160 of the present invention, except in this case; there are three connector cavities 172, 174 and 174'.
FIG. 40A is a tripolar secondary header of the present invention that is similar to FIG. 40, but an oval or elliptical energy dissipating surface 200 has been added. It has two replacement connector cavities 174 and 174'. Cavity 174 is for an abandoned lead, such as an IS-1, a DF-1 so that the abandoned lead conductors and their associated electrodes are safer during MRI scans. In some models cavity 174 could even be DF4 or IS4 or the like, so as to improve MRI compatibility of additional abandoned quadripolar leads. This may seem an unlikely situation to an engineer or other technical person, but physicians specializing in lead extraction not infrequently are presented with infected patients in whom 3 or more leads have been abandoned, in addition to whatever leads continue to be functional. As previously described, connector cavity 172 is to receive a DF4 or IS4 proximal lead connector wherein, one of the lead conductors or other components has failed. Secondary connection cavity 174 and/or 174' is for implantation of a new lead to replace the failed function(s) of the previously implanted IS4 or DF4 lead.
FIG. 40B is a pictorial-electrical diagram derived from FIG. 40A illustrating some possible wiring connections. Referring to connector cavity 172, one can see that the high-voltage proximal contact (HP) 186a has been disconnected from plug 168 and instead routed to the energy dissipating surface 200 by wire 202a. This has the desired effect of connecting the defective conductor of a subsequently inserted lead to the energy-dissipating surface 200 so that it will be safer during MRI scans. A secondary DF-1 connector cavity 174 has been provided for receipt of the proximal connector of a newly implanted high-voltage DF-1 lead, after it has been routed into the superior vena cava (not shown). In this case, leadwire 192a connects the electrode (HP) 198 in the 174 connector cavity to connector plug 168 ring contact electrode 190a. As before, the secondary header 160 proximal connector plug 168 is designed to be inserted into the appropriate AIMD connector cavity. In this case, provision is also made for connecting both conductors of a defective IS-1 lead to the energy dissipating surface (EDS) 200 by means of leadwires 202b and 202c. For example, the atrial lead as previously described in FIGS. 4 and 24 could also have failed and been replaced and 174' provides a place to plug in this abandoned lead and provide an additional MRI safety feature. By extension, instead of the original atrial lead in FIG. 24, the replacement IS-1 ventricular lead could have failed, and could be similarly replaced and made MRI compatible. Further if there had been partial failure of the DF4 lead plus failure requiring replacement of both IS-1 leads in FIG. 24 a four connector port secondary header 160 is readily understood as another configuration. Note that the secondary header 160 connector cavity 174' shown in FIG. 40 provides for both the tip and ring connections (LP') 196a and (LR') 196b to be connected to the energy dissipating surface 200 by way of leadwires 202b and 202c. In this way, all of the abandoned lead conductors are attached to an energy dissipating surface 200 for dissipation of RF energy when the patient is exposed to high-power MRI scans. One is also referred to U.S. Patent 8,000,801 entitled, SYSTEM FOR TERMINATING ABANDONED IMPLANTED LEADS TO MINIMIZE HEATING AND HIGH-POWER ELECTROMAGNETIC FIELD ENVIRONMENTS, the contents of which are incorporated herein by reference. One is also referred to U.S. Patent Publication 2010/0324639 entitled, METHODOLOGY AND APPARATUS TO TERMINATE ABANDONED ACTIVE IMPLANTABLE MEDICAL DEVICE LEADS; and U.S. Patent Publication 2011/0022140 entitled, METHODOLOGY AND APPARATUS TO TERMINATE ABANDONED ACTIVE IMPLANTABLE MEDICAL DEVICE LEADS; and U.S. Patent Publication 2010/0217262 entitled, FREQUENCY SELECTIVE PASSIVE COMPONENT NETWORKS FOR ACTIVE IMPLANTABLE MEDICAL DEVICES UTILIZING AN ENERGY DISSIPATING SURFACE. The contents of all of the aforementioned patent publications are incorporated herein by reference.
FIG. 40C is an electrical line diagram taken from FIG. 40B showing which electrical connections are active and which are inactive. As one can see, in the DF4(-) low profile secondary header 160 extension cavity 172, connection (HP) 186a is inactive, meaning that it is no longer connected to the secondary header connector plug 168 and contact 190a will no longer be connected to the defective lead. Connections (HD) 186b, (LR) 184a and (LP) 184b are in contrast all active, meaning that in the future following appropriate connections and implantation, those will continue to be connected to AIMD circuitry. Importantly, the inactive electrode (HP) 186a, which would have been routed to the proximal high-voltage shocking coil, has instead been connected to the energy dissipating surface 200 by way of leadwire 202a. A connector cavity 174 in the low profile secondary header 160 for a new lead has been provided. This is a DF-1 connection, meaning that a new DF-1 lead can be plugged in and routed down toward the superior vena cava 130 to replace the defective defibrillation coil originally connected to the equivalent electrode (HP) 186a on the partially failed DF4 lead. In addition, there is another connector cavity 174' provided for a low voltage abandoned IS-1 lead, for example lead 104 as previously described in FIG. 24.
In summary, the structure for low profile secondary header 160 as illustrated in FIGS. 40A through 40C combines the present invention with an abandoned lead cap as previously described in U.S. Patent Publication 2010/0324639 .
FIG. 42A is one type of electrical diagram for another embodiment of a triple connector cavity 172, 174 and 174' secondary header 160 of FIG. 41. This type of arrangement would be used, for example, in the case where both of the high-voltage shocking coil conductors of lead 106", as previously illustrated in FIG. 25, have failed. One can see that both DF4(-) electrodes (HP) 186a and (HD) 186b in connector cavity 172 have been disconnected from contacts in plug 168. Accordingly, there are two secondary header DF-1 connector cavities 174 and 174' illustrated. In this case, two new shocking leads would be required. One placed in the superior vena cava 130 and the other placed into the right ventricle 110 in parallel with the existing leads.
FIG. 42B is an electrical line drawing derived from FIG. 42A showing which secondary header connector cavity electrical contacts are active and which are inactive. Of course, in the preferred embodiment, the inactive locations would be connected to an energy dissipating surface 200 as previously described in FIGS. 30A, 38A or 39A. It should also be noted, that in designs where it was decided not to incorporate an energy dissipating surface, then it would not be necessary to provide connector electrode rings for abandoned circuits inside the connector cavity 172. For example, referring to FIG. 42A, the abandoned ring contacts (HP) 186a and (HD) 186b could simply be eliminated from the low profile secondary header 160 which would save some cost in manufacturing and materials.
FIG. 43 is very similar to FIG. 40 except that there are two low profile secondary header 160, connector plugs IS-1 168' and DF4 168 that are designed to be inserted into connector cavities 116b and 118c of AIMD 100 header 114. In this case, the secondary header 160 IS-1 plug 168' provides for an electrical pass-through. This is better understood by referring to FIG. 44A.
FIG. 44A is a pictorial electrical wiring diagram taken from FIG. 43. The physical shape in FIG. 44A has been changed to illustrate that secondary header connector cavities 174 and 174' can be aligned side by side next to connector cavity 172 or on both sides of connector cavity 172, as previously illustrated in FIG. 43. A low profile conforming shape that tightly hugs the device 100 and/or its header 114 is preferred. Referring once again to FIG. 44A, one can see that the IS-1 secondary header connector plug 168' passes its electrical connections straight through to secondary header connector cavity 174'. The purpose of this type of pass-through is so that the new and old leads can all be lined up together, which facilitates winding and dressing the leads together so that they do not splay or cross over and can make for a more compact configuration in a device pocket. In other words, the pass-through feature consisting of connector IS-1 plug 168' and connector cavity 174' is provided as an additional convenience, in order to facilitate parallel lead coiling around the pulse generator, prior to implantation of the pulse generator-secondary header-lead conglomerate into a previously prepared tissue pocket. Secondary header connector cavity 174 is for receipt of a DF-1 lead connector to replace the failed DF4 lead function disconnected at contact (HP) 186a as shown in connector cavity 172.
FIG. 44B is an electrical line diagram taken generally from FIG. 44A further illustrating that the secondary header connector cavity 174' is a simple IS-1 pass-through and that connector cavity 174 provides a contact (HP) 198 for a new DF-1 high-voltage shocking lead (not shown). FIG. 44B also illustrates that the defective high-voltage shocking lead conductor that will appose contact (HP) 186a in connector cavity 172, following insertion of the partially failed DF4 lead connector therein, will have been disconnected from the DF4 secondary header connector plug 168, and thereby will be disconnected from AIMD electronics, following completion of all lead connections to the secondary header 160 and insertion of the secondary header's twin connector plugs 168, 168' into the appropriate pulse generator.
FIG. 45A includes a line diagram of the human heart 102 similar to that previously described in FIG. 5. Also shown is a CRT cardiac pacemaker 100, and a low profile secondary header 160 of the present invention. In this case, the secondary header 160 has one IS4 connector cavity 172 and four IS-1 connector cavities 174, 174', 174" and 174"', as required to correct a complete and total failure of the previously implanted IS4 lead 104"'. The secondary header connector 168 is plugged into the same primary connector cavity in the header block 114, where the IS4 lead connector 104''' was previously plugged. Four new IS-1 leads 180, 180', 180" and 180''' are ready for connection to the IS-1 connector cavities 174, 174', 174" and 174''' of the secondary header 160, after being routed transthoracically, by one of a variety of limited thoracotomy or telescopic-plus port techniques, to sites on or near the epicardial surface of the left ventricle 136 shown as 216 through 216"'. Transthoracic lead placement as described is often referred to as minimally invasive, at least compared to more major surgical procedures requiring the chest wall to be more widely opened through lateral or sternal incisions. The transthoracic leads may exit the chest wall at various locations and are then easily tunneled into the device pectoral or other pocket where their connectors can be conveniently plugged into the low profile secondary header 160.
FIG. 46A is a pictorial electrical wiring diagram taken from the secondary header 160 previously illustrated in FIG. 45. One can see that there is an IS4 connector plug 168 which is designed to be plugged into the AIMD connector cavity which was previously occupied by failed lead 104''' in FIG. 45. Shown are four IS-1 secondary header connector 160 cavities 174, 174', 174" and 174"'. Each of these has a unipolar electrical contact 196, 196', 196" and 196''' for engaging the tip electrode of an IS-1 lead. The four IS-1 contacts just described are then routed to ring contacts 218 through 218''' on secondary header connector plug 168. One can see that all of the contacts inside connector cavity 172 are disconnected from the secondary header's 160 connector plug 168, and so would not be connected to AIMD circuitry, even after plug 168 had been inserted into the AIMD connector cavity and the pin setscrew (not shown) appropriately tightened. In a particularly preferred embodiment, all four of these electrical contacts 197, 197', 197" and 197''' in the connector cavity 172 would be connected to an energy-dissipating surface 200 (not shown). In addition one of the ring electrodes on the connector 168, for example 218, could function as a ground, or even as a common ground to 174, 196 so that one or all three of the remaining secondary connector cavities, for example 174', 174" and 174''' could provide bipolar low voltage pacing and sensing (referenced to common ground 174 or to each other in any combination).
FIG. 46B is an electrical line diagram taken from FIG. 46A showing which electrical contacts are active and which are inactive. As one can see, all of the electrode contact sites 197, 197', 197" and 197''' within connector cavity 172 have been disconnected. It must also be understood that all four of the LV electrode stimulation sites 216 through 216"', as illustrated in FIG. 45, must be referenced to the associated metal pulse generator housing 112 to achieve a common ground and so called unipolar pacing and capture wherein the pulse generator housing is an electrode. The three alternative bipolar configurations described in the preceding paragraph would be far preferred, if the implanted pulse generator system included defibrillation functions, where bipolar sensing is considered of primary importance.
In general as illustrated in FIGS. 26A-29B, 42A-44B, as well as 46A and 46B, the functionality of the secondary header 160 of the present invention can be described in mathematical terms. The mathematical relationship correlates the active and inactive electrical contacts provided by the medical lead connector cavities, residing at the distal end portion of the secondary header, to the active electrical contacts of the secondary header plug residing at the proximal end portion of the secondary header. Therefore, the relationship between the electrical contacts of the distal end connector cavities of the secondary header to that of the proximal end plug of the secondary header can be defined by the mathematical equation: X − S = N ,
FIG. 47 illustrates any of the low profile secondary header 160 illustrated in previous drawings fitted with an RFID chip 220 and RFID antenna 222. In general, this would form a passive RFID tag 221, meaning that it captures all of its energy from an external interrogator or RFID reader. The RFID tag 221 may be placed in any physical location on or within the low profile secondary header 160. In addition, it will be obvious that the low profile secondary header 160 may be slightly enlarged for a section to provide room for the RFID tag 221 including its associated chip 220 and antenna 222. U.S. Patent 7,983,763 describes RFID tags for implanted leads. The contents of the '763 patent are incorporated herein by reference.
A low profile secondary header (160) for an active implantable medical device (AIMD) (100) incorporating a connector cavity having a plurality of electrical contacts, the secondary header (160) comprising a secondary header plug (168) configured for mating physical and electrical insertion into the AIMD connector cavity, the secondary header plug (168) having a plurality of electrical contacts which correspond to the plurality of electrical contacts of the AIMD connector cavity, wherein
the secondary header (160) further comprises:
a secondary header connector cavity (172) having one or more electrical contacts, but less than the number of secondary header plug electrical contacts, conductively coupled to respective secondary header plug electrical contacts; and
at least one replacement lead connector cavity (174) having at least one electrical contact conductively coupled to at least one secondary header plug electrical contact;
characterized in that the secondary header (160) further including an energy dissipating surface electrically connected to one or more electrical contacts of the secondary header connector cavity (172) which are not conductively coupled to the secondary header plug electrical contacts.
The secondary header (160) of claim 1, wherein the energy dissipating surface is either disposed on an exterior surface of a housing for the secondary header connector cavity housing, substantially encircles at least a portion of the secondary header connector cavity housing, or is disposed in a recess formed on the exterior surface of the secondary header connector cavity housing.
The secondary header (160) of any of the preceding claims, including a diverter circuit electrically connected between the energy dissipating surface and the one or more electrical contacts of the secondary header connector cavity (172) which are not conductively coupled to the secondary header plug electrical contacts.
The secondary header (160) of claim 3, wherein the diverter circuit comprises a short, a capacitor, an R-C circuit, an L-C trap, or an R-L-C circuit.
A low profile secondary header (160) of any one of the preceding claims, including an RFID tag affixed to or embedded within the secondary header (160).
The secondary header (160) of any of the preceding claims, wherein the secondary header connector cavity (172) has no electrical contacts conductively coupled to any electrical contact on the secondary header plug.
The secondary header (160) of claim 6, wherein at least one of the secondary header connector cavity electrical contacts is electrically connected to an energy dissipating surface.
EP17193030.8A 2011-03-07 2012-03-07 Secondary header for an implantable medical device incorporating an iso df4 connector and connector cavity and/or an is4 connector and connector cavity Withdrawn EP3284518A1 (en)
EP12158362.9A Division EP2497532A3 (en) 2011-03-07 2012-03-07 Secondary header for an implantable medical device incorporating an ISO DF4 connector and connector cavity and/or an IS4 connector and connector cavity
EP3284518A1 true EP3284518A1 (en) 2018-02-21
EP17193030.8A Withdrawn EP3284518A1 (en) 2011-03-07 2012-03-07 Secondary header for an implantable medical device incorporating an iso df4 connector and connector cavity and/or an is4 connector and connector cavity
EP12158362.9A Withdrawn EP2497532A3 (en) 2011-03-07 2012-03-07 Secondary header for an implantable medical device incorporating an ISO DF4 connector and connector cavity and/or an IS4 connector and connector cavity
"PACEMAKER LEAD TIP HEATING AND ABANDONED AND PACEMAKER-ATTACHED LEADS AT 1.5 TESLA MRI", REFERENCE JOURNAL OF MAGNETIC RESONANCE IMAGING, vol. 33, 2011, pages 426 - 431
"PACEMAKER LEAD TIP HEATING IN ABANDONED AND PACEMAKER-ATTACHED LEADS AT 1.5 TESLA MRI", JOURNAL OF MAGNETIC RESONANCE IMAGING, vol. 33, 2011, pages 426 - 431
CIRC ARRHYTHMIA ELECTROPHYSIOL., vol. 2, 2009, pages 411 - 416
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