Ventricular Pacing Redundancy to Prevent Loss of Capture: A Fail-safe for Pacemaker-Dependent Patients

ABSTRACT: Background. Patients who are entirely dependent on ventricular pacing are typically at the mercy of a single ventricular lead and pacemaker output in order to provide physiologic support. This study presents a number of high-risk cases (two of which previously exhibited failure with standard pacing) in which ventricular pacing redundancy (VPR) was utilized in order to provide additional backup. VPR was achieved using a variety of configurations, all of which employed a second ventricular lead and the potential for additional ventricular pacing. Seven cases are presented in which some form of VPR was successfully implemented in order to prevent device failure and resultant hemodynamic collapse. J INVASIVE CARDIOL 2010;22:247–250 Key words: pacemaker, defibrillator, biventricular pacing, loss of capture, redundancy, fail-safe, complete heart block Current permanent pacemaker systems (including implantable cardioverter-defibrillators) are limited in their ability to provide ventricular pacing in the event of pacemaker/lead failure in patients who are completely pacemaker-dependent. On rare occasions, patients have received some form of ventricular pacing redundancy (VPR) in order to prevent loss of ventricular capture in those at high risk. In this retrospective study, we reviewed our experience with VPR as well as its potential broader applications. This study was approved by the Winthrop University Institutional Review Board. Seven cases from the last 4 years were reviewed using the Winthrop University Hospital Electrophysiology Data Management System. Patient characteristics, device configurations and follow up are reviewed below. Please note for clarification purposes, the age of the patient at the time of VPR implant is indicated in each case vignette; tables indicate the patient’s current age at the time of follow up. Also note that all data are reported as mean ± standard error of the mean (SEM). Case 1. An active 89-year-old male who was completely pacemaker-dependent underwent lead revision and device replacement of a dual-chamber pacemaker. While he was on a cross-country flight, he experienced syncope occasionally with prolonged asystolic episodes. He presented to a regional hospital and was found to have lead failure with intermittent loss of capture and resultant hemodynamic instability. At that institution, he had a second dual-chamber pacing system implanted on the contralateral side. The older system was left in place per the patient’s choice, though it was programmed off in order to provide emergency backup should pacemaker failure reoccur (although the former device would require reprogramming in this event). This patient is currently 93 years old and continues to remain active. The older pacing system has been tested and is fully functional, but continues to be programmed off. This former system may extend pacing longevity in this very elderly patient and may be programmed back on once the Elective Replacement Indicator (ERI) is reached with the more recent system. This case provided the impetus for our continued development of the clinical applications for VPR as demonstrated through the following clinical cases in patients who essentially were entirely pacemaker-dependent without a sustainable underlying rhythm. Case 2. An 85-year-old female had a history of drug-refractory symptomatic atrial fibrillation and an atrial-ventricular junction (AVJ) ablation with resultant complete heart block (CHB) requiring permanent pacemaker implantation. Later in her life, she developed recurrent near syncopal episodes and was found to have inducible sustained monomorphic ventricular tachycardia during an electrophysiological study. The patient had a device upgrade and a defibrillator was implanted. The old right ventricular (RV) lead was left intact and capped off. The following day, she developed intermittent loss of RV pacing capture and required a temporary pacing wire. The patient was referred for lead revision. The pacing from the implantable cardioverter-defibrillator (ICD) system was initially set up through a new RV ICD lead. On inspection, the RV lead had a micro-dislodgement which required repositioning. In order to provide a fail-safe, the old RV pacemaker lead was inspected. A small insulation defect was observed and repaired with a silicone repair kit and sleeve. The pacing and sensing function of this lead were excellent. The old RV pacing lead was connected to the left ventricular (LV) port and the new RV ICD lead, which was repositioned, was connected to the RV port of the device. The biventricular ICD was used to provide redundancy in the system in order to avoid recurrence of pacing malfunction in this pacemaker-dependent patient. She has been followed for over one and one-half years with this redundant pacing system and has had no further episodes of pacing failure. Case 3. An 83-year-old female who was completely pacemaker dependent experienced an episode of presyncope. On pacemaker interrogation, there were 17 beats of ventricular tachycardia. The patient underwent an electrophysiology study and was found to have inducible sustained monomorphic ventricular tachycardia. An ICD upgrade was required in this patient. Given that the patient was completely pacemaker-dependent, a biventricular ICD was implanted to take advantage of the old functional RV pacemaker lead. Here, as in the previous case, the 5-year-old RV lead was plugged into the RV port and the new RV ICD lead was placed in the LV port. This setup allowed us to take advantage of the two implanted RV leads by providing VPR with over 3 months of follow up. After implantation, there have been no known complications or evidence of system failure. Case 4. A 55-year-old female with a history of an ischemic cardiomyopathy, ventricular tachycardia, as well as drug-refractory atrial fibrillation and an AV junction ablation, was referred for ICD/lead revision due to ventricular oversensing. The patient had a very old RV pacing lead which was freed up and tested during the procedure. The lead, albeit old, exhibited excellent pacing and sensing. This old pacing lead was used as the RV pace-sense in the biventricular device. A new RV ICD lead was plugged into the LV port of the new ICD. This configuration was used to provide additional back-up pacing since the patient was entirely pacemaker-dependent. The patient has subsequently been followed for 1 year without any device/lead failure, including the old RV pace-sense lead, which was over 7 years old. Case 5. A 78-year-old male with ischemic cardiomyopathy, LV ejection fraction of 30%, New York Heart Association Class III congestive heart failure and on optimal medical therapy underwent an AV junction ablation for drug-refractory atrial fibrillation. Post procedure, while in complete heart block, the patient had loss of ventricular capture due to a rise in ventricular pacing thresholds. The patient subsequently underwent an upgrade to a biventricular ICD such that new RV and LV pacing leads were inserted. The old RV ICD pace-sense lead was attached to the atrial port and programmed off. The new RV and LV leads were used for the RV/LV pace-sense, respectively, and the old RV ICD lead was used for high-voltage therapy. VPR was achieved through biventricular pacing with the potential to provide a third ventricular output in an emergency (i.e., if lead dislodgement or increased threshold occurred, then the old RV pace-sense could be programmed to pace the RV) with both of the standard leads. This difficult approach, with a more stable configuration, was necessary in order to prevent severe hemodynamic instability in a completely pacemaker-dependent patient. All involved parties were informed of the configuration and a note was programmed in the device which appears immediately following interrogation. The patient is alive and well after 3 months of follow up. Case 6. An 82-year-old female with a history of atrial fibrillation and syncope initially presented to the hospital after a traumatic syncopal episode with resultant facial trauma. The patient underwent a tilt-table test which was normal. Subsequently, an implantable loop recorder was placed which revealed atrial fibrillation with rapid ventricular response. The patient underwent an AV junction ablation with resultant complete heart block and 2 RV leads were implanted in the RV outflow tract in order to provide VPR. The patient is alive and well approximately 2 months following the procedure. Case 7. An 84-year-old female had a past medical history of syncope from complete heart block and permanent pacemaker implanted. The patient continues to have recurrent syncope from ventricular tachycardia and underwent device upgrade to an implantable defibrillator. She was completely pacemaker-dependent with no underlying escape rhythm, so the decision was made to implant a biventricular device to provide a redundant pacing system. The old RV lead was connected to the LV port and the new RV lead was connected to the RV port of the biventricular device. Table 1 shows the patients’ clinical characteristics including current age, gender, presence of atrial fibrillation, and LV ejection fraction. The mean age was 80 ± 12 years; 5 were women and 2 were men. All but 2 had atrial fibrillation, and the mean LV ejection fraction was 50 ± 13%. Table 2 shows the old original RV lead characteristics. Most leads were older than 5 years and had the potential for future failure, thus redundancy seemed appropriate. This is especially important given the fact that a new ventricular lead would have the potential for an acute rise in threshold and/or dislodgement with resultant hemodynamic collapse. Table 3 shows the types of RV leads (active or passive fixation) and pacing configurations used in this series. The mean follow up from VPR was 386 ± 196 days. Table 4 shows, the potential effect on device longevity using a VPR system (estimated by the pulse generator technical services of Medtronic, Inc., Minneapolis, Minnesota). In general, each device lost about 20% of the longevity utilizing a VPR configuration. An exception was patient number 6 who received a biventricular pacemaker rather than a single-chamber device (the originally intended pulse generator). The larger battery capacity of a biventricular pacemaker actually resulted in enhanced longevity with the VPR configuration as compared with a standard single-chamber pacemaker. Discussion. The series identified in this retrospective review demonstrates the evolution and utility of ventricular pacing redundancy in order to prevent loss of capture in patients who are pacemaker-dependent. The second device implanted in case 1, in which the redundant system was placed at an outside institution and the old system was left intact, was the result of the patient’s preference. The lead dislodgement complication which occurred in case 2, where the patient underwent a pacemaker upgrade to an ICD, resulted in a VPR configuration using the old RV pacing lead and a new repositioned RV ICD lead, all plugged into a biventricular pacing device. Case 5 was also the result of loss of ventricular capture following an AV junction ablation in a patient with a 3-month-old RV lead. This latter system had the potential to provide ventricular pacing from 2 RV sites and 1 LV site (“tri-ventricular pacing”), albeit 1 RV lead was programmed off and merely represented an additional fail-safe that would require reprogramming in order to effect pacing (much like our first patient). The evolution provided in this series demonstrates the application of a simple VPR methodology by utilizing a biventricular pulse generator, which combines the use of the old and new leads. The old lead may have a higher risk of failure (due to its age), and the new lead has a higher risk of dislodgement or threshold elevation with potential for loss of capture. VPR using a biventricular device provides at least dual output and lead redundancy with enhanced safety should one RV lead fail. It should be noted that this type of redundancy has widely been utilized in patients who qualify for cardiac resynchronization therapy and are pacemaker-dependent. The difference in our series is that most (if not all of our patients) failed to have a Class I indication for cardiac resynchronization therapy. Previously, Villain and colleagues describes a case of VPR utilizing a dual-chamber pacemaker in which the atrial lead was redundantly placed in the right ventricle of a 4-year-old boy with congenital complete atrioventricular block. They implanted two separate RV leads and connected them to a dual-chamber pacemaker. The two pacing channels of the dual-chamber pacemaker, one lead connected to the atrial port (RV apex pacing) and the other to the ventricular port (RV infundibular pacing), were programmed to compensate in case of lead failure. The pacemaker was programmed to DDD mode with a fixed atrioventricular delay of 30 ms. The system had no potential for AV synchrony. ¹ In our “tri-ventricular” cases, when necessary, the old RV pace-sense component of the ICD lead (a third ventricular lead) could be activated similarly by programming on the atrial channel with a short AV delay. Several other investigators have utilized two independent pacemaker systems in patients. ^2–4 These older methods have subjected patients to additional leads/devices and sites, all of which potentially contribute to an increase in the potential for infection. A single VPR system with redundant leads, much like in cases 2–7, appears to provide the answer for these high-risk pacemaker-dependent patients. One important limitation, however, is the additional energy requirement and subsequent battery drainage of that provided by the system. The ICD and the pacing pulse generator utilized in each of our cases were from Medtronic, Inc. Utilizing standard pacing systems with average pacemaker outputs on right and left ventricular channels, the device longevity was estimated by Medtronic Technical Services to decrease by approximately 20% (as seen in Table 4). This is the difference between standard and VPR pacing. Conclusion. In summary, ventricular pacing redundancy in pacemaker-dependent patients may prevent adverse outcomes and provide additional safety to these patients. It is possible to build ventricular redundancy into a single ventricular lead (i.e., redundant conductors) such that a more typical dual-chamber system may be implanted. In addition, energy conservation could be obtained by pacing from one ventricular lead (or conductor) and sensing an evoked response from another lead, thereby assuring pacing capture. Absence of an evoked response (an indicator of ventricular capture) could trigger a paced output from the second lead. This novel VPR system, which could be designed to be more energy-efficient, will require further research and development. Perhaps a registry for patients, such as described in this case series, could be designed to categorize and prospectively evaluate both the indications and solution. In this manner the risks, benefits, costs, complications, system longevity, patient satisfaction and quality of life, and so forth, of utilizing a VPR solution could be measured both qualitatively and quantitatively against referenced benchmarks.

References

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__________________________________________________________________ From the Division of Cardiology, Winthrop University Hospital, Mineola, New York and *New York College of Osteopathic Medicine, Old Westbury, New York (as of 5/24/10). The authors report no conflicts of interest regarding the content herein. Manuscript submitted March 31, provisional acceptance give April 15, final version accepted April 19, 2010. Address for correspondence: Todd J. Cohen MD, Division of Cardiology, Division of Cardiology, Winthrop University Hospital, 120 Mineola Blvd., Suite 500, Mineola, New York 11501.