ASAIO Journal 2014
Clinical Cardiovascular
Catheter Ablation for Ventricular Tachyarrhythmias in Patients Supported by Continuous-Flow Left Ventricular Assist Devices Arthur R. Garan,* Vivek Iyer,* William Whang,* Kanika P. Mody,* Melana Yuzefpolskaya,* Paolo C. Colombo,* Rosie Te-Frey,† Hiroo Takayama,† Yoshifumi Naka,† Hasan Garan,* Ulrich P. Jorde,* and Nir Uriel*
Ventricular arrhythmias (VAs) are common after implantation of a left ventricular assist device (LVAD) and in a subset of patients may be refractory to medication. Morbidity from VA in this population includes right ventricular failure (RVF). We sought to evaluate the efficacy of catheter ablation for VA in patients with LVAD. A retrospective analysis of patients supported by continuous-flow LVAD referred for catheter ablation of ventricular tachycardia (VT) between 2008 and the present was performed. Seven patients were referred for VT ablation an average of 236 ± 292 days after LVAD implantation. Three patients (42.9%) developed RVF in the setting of intractable arrhythmias. A transfemoral approach was used for six patients (85.7%) and an epicardial for one patient (14.3%). The clinical VT was inducible and successfully ablated in six patients (85.7%). The location of these arrhythmias was apical in three cases (42.9%). A total of 13 VTs were ablated in seven patients. Although the majority had reduction in VA frequency, recurrent VAs were observed in six patients (85.7%). One patient (14.3%) experienced a bleeding complication after the procedure. For patients with a high VA burden after LVAD implantation, VT ablation is safe and feasible, but VA frequently recurs. ASAIO Journal 2014; 60:311–316.
respect to both survival and quality of life.1 Furthermore, advances in mechanical circulatory support technology have further improved long-term outcomes in this patient population.2,3 Continuous-flow left ventricular assist devices (CF-LVAD) have supplanted the older, pulsatile-flow pumps. As more patients undergo implantation of a long-term CF-LVAD, new dilemmas in clinical management have been identified. One problem frequently encountered in patients supported by CF-LVAD is ventricular arrhythmia (VA). We have previously shown that although VAs are common in patients supported by CF-LVAD, they are also well tolerated acutely in this population.4 However, recurrent, intractable VA can result in frequent ICD therapies which carry significant morbidity. Furthermore, intractable VA may also result in hemodynamic compromise despite CF-LVAD presence because of worsening right ventricular failure. In the case of frequent, intractable VA despite antiarrhythmic therapy in patients supported by CF-LVAD, catheter ablation of the ventricular tachycardia (VT) remains an option for management. Several centers have reported success with this procedure to reduce the frequency of such arrhythmias, although there remain relatively little data to guide the management decisions with this clinical scenario.5–9 Methods
Key Words: left ventricular assist device, ventricular tachycardia, ablation
We retrospectively reviewed charts of patients who had undergone implantation of a long-term CF-LVAD between January 1, 2008 and December 31, 2012. We identified those who had undergone electrophysiology study and catheter ablation for VT after CF-LVAD implantation. Demographic information and clinical information including ventricular dimensions, medications, and electrophysiologic parameters were recorded. In addition, details of the procedure were obtained. Ventricular arrhythmia was defined as any of the following: any ventricular tachyarrhythmia (VT or ventricular fibrillation [VF]) that received appropriate therapy (antitachycardia pacing [ATP] or shock) from an ICD or was sustained for greater than 30 seconds in the absence of effective treatment. VT storm was defined as any of the following: three or more appropriate tachytherapies or two or more episodes of stable VT without tachytherapy in a 24 hour period, or VT occurring immediately after termination, or sustained and nonsustained VT resulting in a total number of ventricular ectopic beats greater than sinus beats in a 24 hour period. Right ventricular failure was defined by the need for right ventricular assist device placement, prolonged pulmonary vasodilators, or prolonged inotrope use.
In patients with advanced heart failure, left ventricular assist devices (LVADs) have demonstrated significant benefits with
From the *Department of Medicine, Division of Cardiology, Columbia University Medical Center, New York, New York; and †Department of Surgery, Division of Cardiothoracic Surgery, Columbia University Medical Center, New York, New York. Submitted for consideration October 21, 2013; accepted for publication in revised form February 3, 2014. Ulrich P. Jorde contributed equally as senior author. Disclosure: Dr. Naka is a consultant for Terumo Heart Inc., Thoratec Corp., and Cardio-MEMS. Dr. Jorde has received consulting fees from Thoratec Corp. Dr. Uriel has received consulting fees from Heartware, Inc. The other authors have no conflicts of interest to report. Reprint Requests: Nir Uriel, MD, Mechanical Circulatory Support Program, Division of Cardiology, Columbia University Medical Center–New York-Presbyterian Hospital, 622 West 168th Street, PH-12, Room 134, New York, NY 10032. Email: [email protected], [email protected]. Copyright © 2014 by the American Society for Artificial Internal Organs DOI: 10.1097/MAT.0000000000000061
311
312 GARAN et al. Table 1. Baseline Demographics of Patients Undergoing VTA Patient 1 2 3 4 5 6 7
Age (Years)
Sex
Cardiomyopathy
LVAD Indication
VTA Indication
Days After LVAD Implantation
76 50 52 75 66 62 74
M M M M M M M
Ischemic Nonischemic Nonischemic Ischemic Ischemic Ischemic Ischemic
DT BTT BTT DT BTT BTT DT
Recurrent ICD firing RV failure Recurrent ICD firing Recurrent ICD firing Recurrent ICD firing RV failure RV failure
24 8 55 453 177 133 802
BTT, bridge-to-transplant; DT, destination therapy; LVAD, left ventricular assist device; M, male; RV, right ventricle; VTA, ventricular tachycardia ablation.
Electrophysiology study and VT ablation (VTA) were performed at our institution. The patient’s ICD was reprogramed to deactivate tachycardia therapies at the beginning of each case. However, the level of hemodynamic support was not changed periprocedurally (i.e., no LVAD reprograming was performed and no mechanical right ventricular support was used). For cases in which presenting rhythm was not VT, induction using programmed stimulation with up to triple extrastimuli was performed from the right ventricle; if VT was noninducible, a second site was generally used. Only monomorphic VTs were targeted, including the clinical VT (if clinical morphology was known or was the presenting rhythm); cardioversion was performed for induced sustained polymorphic VT or VF. Left ventricular access was obtained either via retrograde aortic or transseptal approach with femoral vascular access or via sternotomy if epicardial access was required. Mapping was performed during monomorphic VTs with stable hemodynamics in all cases, using CARTO (Biosense Webster, Diamond Bar, CA) or EnSite NavX (St. Jude Medical, St. Paul, MN) electroanatomic mapping systems. An entrainment or activation mapping strategy during VT was preferred.10 A pure substrate-based approach was elected in cases where VT was inducible. An irrigated 3.5 mm radiofrequency (RF) catheter was used for mapping and lesion delivery (Thermocool SF; Biosense Webster) using power delivery of up to 40 Watts. The procedure concluded at the operator’s discretion after 1) acute termination of the clinically observed VT during RF delivery (or RF delivery at a site where mechanical termination occurred), followed by substrate modification at adjacent sites within the scar, 2) targeting of additional induced monomorphic VTs, or 3) noninducibility of sustained monomorphic VTs with the programmed stimulation protocol.
Results Patient Characteristics Of 224 patients who underwent implantation of a long-term CF-LVAD between January 1, 2008 and December 31, 2012, we identified seven patients (3.1%) who had undergone electrophysiology study and VTA while on CF-LVAD support. Currently at our institution, 23% of CF-LVAD recipients experience at least one VA postoperatively and 4% experience five or more. Patients underwent VTA on average 236 ± 292 days after CF-LVAD implantation. The average age of the patients was 65.0 ± 10.8 years and all (100%) were men (Table 1). Five (71.4%) of the seven patients had an ischemic cardiomyopathy and four (57.1%) had undergone CF-LVAD implantation as a bridge-to-transplant (BTT). The average left ventricular end-diastolic dimension (LVEDd) was 6.6 ± 0.7 cm. All patients (100%) had experienced at least one VA preoperatively, although only one patient (14.3%) had undergone VTA. Five patients (71.4%) had experienced VT storm before CF-LVAD implantation and four of these patients experienced VT storm within 1 week before surgery. At the time of VTA, all patients (100%) were being treated with beta-blockers and six (85.7%) were being treated with amiodarone. In addition, five (71.4%) were receiving either mexilitene or lidocaine and two (28.6%) were receiving other antiarrhythmic medications (quinidine for one patient and propafenone for another patient; Table 2). The indication for VTA was recurrent ICD firings in four patients (57.1%) and right heart failure caused by refractory arrhythmia in three patients (42.9%). All three patients whose indication for VTA was RV failure had perioperative RV failure and two of the four patients whose indication was recurrent ICD firing had perioperative RV failure. Of those with right
Table 2. Electrophysiologic History of Patients Undergoing VTA Patient 1 2 3 4 5 6 7
Beta-Blocker
Amiodarone
Mexilitene, Lidocaine
Other AAD
VA Pre-LVAD
VT Storm Pre-LVAD
VTA Pre-LVAD
CRT-D
Yes Yes Yes Yes Yes Yes Yes
Yes Yes Yes Yes Yes Yes No
No Yes Yes Yes Yes No Yes
No Propafenone Quinidine No No No No
Yes Yes Yes Yes Yes Yes Yes
Yes Yes Yes No Yes Yes No
No Yes No No No No No
Yes Yes Yes Yes Yes Yes Yes
AAD, antiarrhythmic drug; CRT-D, cardiac resynchronization therapy-defibrillator; LVAD, left ventricular assist device; VA, ventricular arrhythmia; VT, ventricular tachycardia; VTA, ventricular tachycardia ablation.
313
15.5 Acute termination with RFA During VT Inferior/apical 7
1, 1
Lateral/apical Inferior/basal 5 6
LVAD, left ventricular assist device; OHT, orthotopic heart transplant; RFA, radiofrequency ablation; SR, sinus rhythm; VA, ventricular arrhythmia; V pacing, ventricular pacing; VT, ventricular tachycardia.
Alive on LVAD support Less frequent No
No Yes
None Groin hematoma, difficult defibrillation None Not obtained Not obtained Acute termination with RFA Acute termination with RFA During VT During VT
Inferior/mid 4
1, 1 1, 1
During VT
Lateral/basal 3
4, 4
During VT
Lateral/apical 2
5, 1
Inferior/basal 1
6, 4
Less frequent Less frequent
Expired on LVAD support Bridged to OHT Bridged to OHT Less frequent Yes None 25
No change Yes None 36
No change Yes None 13
RFA at site of mechanical termination RFA at site of mechanical termination Acute termination with RFA
Less frequent Yes None 38 Clinical VA not inducible
During SR/ V pacing During VT
Recurrent VA Complications Fluoro Time (min) Mode of Termination Mapping Performed VA Induced, Ablated
The average time on CF-LVAD support after VTA was 149 ± 108 days. Five patients (71.4%) had reduction in the burden of VA after the VTA. Of these patients, one (14.3%) was without VA entirely until orthotopic heart transplant (OHT), whereas four (57.1%) had at least one recurrent VA. Two patients (28.6%) who had ablation of the clinical arrhythmia continued to have VA after the procedure without reduction in the VA burden despite acute success of the VTA. Three patients (42.9%) expired on LVAD support; of these, one had undergone LVAD implantation as BTT and the other two patients as destination therapy (DT). The causes of death included right ventricular failure leading to multi-organ failure in two patients and device-related death in another. One patient (14.3%) remains on LVAD support as DT. Three patients (42.9%) were successfully bridged to OHT.
Location of Clinical VA
Outcomes
Table 3. Procedural Characteristics and Clinical Outcomes
Five (71.4%) of the procedures were performed via retrograde aortic approach, whereas one (14.3%) was performed via transseptal approach and one (14.3%) via an epicardial approach requiring re-operative median sternotomy 8 days after LVAD implantation. An epicardial approach was used in this case because the patient had undergone VTA before LVAD implantation and was felt to have a substantial burden of epicardial VT substrate. Six patients (85.7%) underwent entrainment or activation mapping during VT, whereas a pure substrate-based strategy was used in one (14.3%) case (Table 3). Intravenous heparin was the procedural anticoagulation strategy in all patients (100%); in addition, five patients (71.4%) were also within the therapeutic range of warfarin. The procedure was performed with general anesthesia in two patients (28.6%) and moderate sedation in five patients (71.4%). A total of 19 VTs were induced and 13 were ablated. In six (85.7%) of the procedures, the clinical VT was inducible or present at the time of ablation. Examples of clinical tachycardias are presented in figure 1. The foci of the clinical tachycardias were left ventricular: lateral/apical in two patients (28.6%), inferior/basal in two (28.6%), inferior/apical in one (14.3%), lateral/basal in one (14.3%), and inferior/mid-ventricular in one (14.3%). Two of three patients with VT localized to the apical region and two of four patients with VT localized to other areas of the myocardium had evidence of migration of the inflow cannula position on chest X-ray between the time of implant and the time of VTA. In four instances, the procedure was terminated after acute termination of the clinical arrhythmia occurred during RF delivery; in two instances, the procedure concluded after termination of the clinical arrhythmia and targeting of multiple other inducible monomorphic tachycardias; and in one instance, the procedure was terminated after the clinical arrhythmia could no longer be induced after RF delivery.
Effect on VA Frequency
Procedural Characteristics
1, 1
Long-Term Outcome
heart failure as the indication, one patient required right ventricular assist device placement and two were treated with pulmonary vasodilators for a prolonged period of time. The right ventricular assist device was placed 5 days after VTA which, despite achieving acute success, did not resolve the right ventricular failure. The patient remained on biventricular support until the time of transplant.
Expired on LVAD support Expired on LVAD support Bridged to OHT
CATHETER ABLATION FOR VT
Patient
314 GARAN et al.
Figure 1. Examples of clinical ventricular tachycardia for patients referred for catheter ablation. A and B: These 12 lead ECGs were obtained from patients who underwent successful ablation of the arrhythmias while on continuous-flow left ventricular assist device support. The ECG in (B) represents a tachycardia which was localized to the apical region of the left ventricle.
Safety There were no intraprocedural complications during VTA. In one instance (14.3%), there was difficulty in defibrillating the patient resulting in prolonged periods of VF. Defibrillation required two sets of defibrillator pads. This patient ultimately tolerated the procedure and the prolonged period of VF well. No patients sustained damage to the ventricular assist device or its connection to the myocardium even when the procedure was performed as few as 8 days after CF-LVAD implantation. One patient (14.3%) developed a groin hematoma which required transfusion of 2 units of packed red blood cells. No patients had worsening renal function after the procedure. Finally, no patients died during or within the 30 days after the procedure. Discussion Herein, we present a series of seven patients supported with long-term CF-LVAD with recurrent VA affecting the quality of life and morbidity of the patients. Indications for VTA were recurrent, appropriate ICD firing despite medical therapy and right heart failure as a result of intractable VA. Our data indicate that catheter ablation of VT may be performed safely via retrograde or epicardial approach with modest efficacy in reducing the burden of VA while on CF-LVAD support.
Although VAs after CF-LVAD implantation are common,4,11–18 only 3.1% of CF-LVAD recipients at our center had such significant burden of VA that VTA was undertaken. These results are similar to those reported by multiple centers,5,6 although our data include exclusively patients with continuous-flow pumps. Whether different pumps (i.e., pulsatile vs. different continuous-flow designs) have different effects on the inci dence and significance of VA is unknown. All of the patients who underwent VTA while on long-term CF-LVAD support had at least one VA before surgery, but only one had undergone VTA preoperatively. Interestingly, a history of VT storm was common among our cohort, a finding also noted by Herweg et al.5 Furthermore, the majority of our patients had experienced VT storm in the week before surgery. This suggests that patients whose need for mechanical circulatory support is largely due to electrical instability remain at risk for significant arrhythmias that require further advanced treatment strategies postoperatively. Our data are novel in that they highlight one of the morbidities associated with intractable VA: right ventricular failure. Almost half of our patients were referred for VTA because of right ventricular failure which can occur even with slower VAs when they become intractable. Whether patients with right ventricular failure attributable to intractable arrhythmias fare as well as patients without this complication after has not been
315
CATHETER ABLATION FOR VT
previously studied. In our series, all patients with right ventricular failure had recurrence of VA after the procedure and one continued to have VA at the same frequency as had been experienced preprocedurally. Importantly, two complications were noted: both postprocedural bleeding and difficulty with defibrillation during the procedure occurred in our series. However, neither complication resulted in permanent morbidity or mortality. Bleeding complications in this patient population remain a concern given the need for anticoagulation and the acquired von-Willebrand syndrome observed after device implantation.19 One patient could not easily be defibrillated after the initiation of ventricular fibrillation with programmed stimulation. Multiple shocks were unsuccessful at restoring sinus rhythm, and it was only when two sets of pads were used that VF was terminated. It is worthwhile to note that this prolonged arrhythmia did not result in hemodynamic collapse, highlighting one potential advantage to undertaking VTA in patients with a CF-LVAD. Indeed, percutaneous temporary mechanical support has been used more frequently to facilitate VTA.20,21 Although this difficulty is not limited to patients with CF-LVAD, this observation raises a question about the effects of CF-LVAD implantation on the defibrillation threshold (DFT). Although multiple centers have reported increases in sensing and stimulation threshold after LVAD implantation, currently no data exist regarding the effects on DFT.22,23 Overall, VTA was acutely successful in the majority of cases. Most patients had ablation of the clinical VT, and the majority had a reduction in the frequency of their VA after the procedure. However, that this subset of patients was particularly prone to VA after CF-LVAD implantation is underscored by the fact that even after successful ablation, VAs still recurred in the majority of patients. Although the rate of acute ablative success in our series is similar to those in other published reports, the rate of recurrence appears higher.5,6 There may be multiple reasons for this. One possible reason is that time on support after VTA was longer in our series than that in other published reports. Second, it is also possible that closer surveillance allowed us to detect arrhythmias that would have otherwise gone undetected, such as successful ATP events. Some of the patients in our study were enrolled in a prospective study quantifying VA in patients with LVAD and frequent surveillance was performed even in the absence of clinically recognized arrhythmias. Finally, it is possible that our patients had a greater burden of arrhythmias with more arrhythmia substrate or more triggers such as right heart failure. Whether recurrent VAs included those that were induced but not ablated during the procedure is unknown. It is also of interest that the origin of the clinical VA was apical—possibly related to the inflow cannula—in about one half of patients, a finding that differs from previously published reports which included earlier generation pumps.11 Last, the time course of the clinically significant arrhythmias post-LVAD is of interest. Although the presence of preoperative VA is known to be the strongest predictor of postoperative VA,4 the timing of these events is less predictable. Although some patients had a heavy burden of VA in the immediate postoperative period requiring VTA, others developed a significant burden of VA requiring the procedure more than 2 years after surgery.
Limitations The retrospective nature of our study limited our ability to detect all VAs for each patient, making it difficult to quantify the magnitude of the effect of the procedure on VAs. Furthermore, device settings were not standardized so that patients with more aggressive settings might have inflation of the number of VAs experienced if their ICD device was delivering tachytherapies for slower or shorter VA. Last, these data represent a single-center experience in small cohort of patients; whether our findings can be applied to the general population of patients with CF-LVAD is unknown. Conclusions Although VAs are common after CF-LVAD implantation, a small subset of patients has refractory VA requiring more advanced antiarrhythmic therapies. Although these arrhythmias are well tolerated acutely, they are not without morbidity which includes right ventricular failure. For such patients, endo- or epicardial ablation of the VA may be safely performed when medical therapy is insufficient to control the arrhythmia burden. However, despite acute success of this procedure, VA frequently recurs. References 1. Rose EA, Gelijns AC, Moskowitz AJ, et al; Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure (REMATCH) Study Group: Long-term use of a left ventricular assist device for end-stage heart failure. N Engl J Med 345: 1435–1443, 2001. 2. Slaughter MS, Rogers JG, Milano CA, et al; HeartMate II Investigators: Advanced heart failure treated with c ontinuous-flow left ventricular assist device. N Engl J Med 361: 2241–2251, 2009. 3. Garatti A, Bruschi G, Colombo T, et al: Clinical outcome and bridge to transplant rate of left ventricular assist device recipient patients: Comparison between continuous-flow and pulsatileflow devices. Eur J Cardiothorac Surg 34: 275–280, 2008. 4. Garan AR, Yuzefpolskaya M, Colombo PC, et al: Ventricular arrhythmias and implantable cardioverter-defibrillator therapy in patients with continuous-flow left ventricular assist devices: Need for primary prevention? J Am Coll Cardiol 61: 2542–2550, 2013. 5. Herweg B, Ilercil A, Kristof-Kuteyeva O, et al: Clinical observations and outcome of ventricular tachycardia ablation in patients with left ventricular assist devices. Pacing Clin Electrophysiol 35: 1377–1383, 2012. 6. Cantillon DJ, Bianco C, Wazni OM, et al: Electrophysiologic characteristics and catheter ablation of ventricular tachyarrhythmias among patients with heart failure on ventricular assist device support. Heart Rhythm 9: 859–864, 2012. 7. Osaki S, Alberte C, Murray MA, et al: Successful radiofrequency ablation therapy for intractable ventricular tachycardia with a ventricular assist device. J Heart Lung Transplant 27: 353–356, 2008. 8. Dandamudi G, Ghumman WS, Das MK, Miller JM: Endocardial catheter ablation of ventricular tachycardia in patients with ventricular assist devices. Heart Rhythm 4: 1165–1169, 2007. 9. Emaminia A, Nagji AS, Ailawadi G, Bergin JD, Kern JA: Concomitant left ventricular assist device placement and cryoablation for treatment of ventricular tachyarrhythmias associated with heart failure. Ann Thorac Surg 92: 334–336, 2011. 10. Stevenson WG, Khan H, Sager P, et al: Identification of reentry circuit sites during catheter mapping and radiofrequency ablation of ventricular tachycardia late after myocardial infarction. Circulation 88(4 Pt 1): 1647–1670, 1993.
316 GARAN et al. 11. Ziv O, Dizon J, Thosani A, Naka Y, Magnano AR, Garan H: Effects of left ventricular assist device therapy on ventricular arrhythmias. J Am Coll Cardiol 45: 1428–1434, 2005. 12. Refaat M, Chemaly E, Lebeche D, Gwathmey JK, Hajjar RJ: Ventricular arrhythmias after left ventricular assist device implantation. Pacing Clin Electrophysiol 31: 1246–1252, 2008. 13. Cantillon DJ, Tarakji KG, Kumbhani DJ, Smedira NG, Starling RC, Wilkoff BL: Improved survival among ventricular assist device recipients with a concomitant implantable cardioverter-defibrillator. Heart Rhythm 7: 466–471, 2010. 14. Refaat MM, Tanaka T, Kormos RL, et al: Survival benefit of implantable cardioverter-defibrillators in left ventricular assist device-supported heart failure patients. J Card Fail 18: 140– 145, 2012. 15. Oswald H, Schultz-Wildelau C, Gardiwal A, et al: Implantable defibrillator therapy for ventricular tachyarrhythmia in left ventricular assist device patients. Eur J Heart Fail 12: 593–599, 2010. 16. Bedi M, Kormos R, Winowich S, McNamara DM, Mathier MA, Murali S: Ventricular arrhythmias during left ventricular assist device support. Am J Cardiol 99: 1151–1153, 2007. 17. Andersen M, Videbaek R, Boesgaard S, Sander K, Hansen PB, Gustafsson F: Incidence of ventricular arrhythmias in patients on long-term support with a continuous-flow assist device (HeartMate II). J Heart Lung Transplant 28: 733–735, 2009.
18. Ambardekar AV, Allen LA, Lindenfeld J, et al: Implantable cardioverter-defibrillator shocks in patients with a left ventricular assist device. J Heart Lung Transplant 29: 771–776, 2010. 19. Uriel N, Pak SW, Jorde UP, et al: Acquired von Willebrand syndrome after continuous-flow mechanical device support contributes to a high prevalence of bleeding during long-term support and at the time of transplantation. J Am Coll Cardiol 56: 1207–1213, 2010. 20. Abuissa H, Roshan J, Lim B, Asirvatham SJ: Use of the Impella microaxial blood pump for ablation of hemodynamically unstable ventricular tachycardia. J Cardiovasc Electrophysiol 21: 458–461, 2010. 21. Friedman PA, Munger TM, Torres N, Rihal C: Percutaneous endocardial and epicardial ablation of hypotensive ventricular tachycardia with percutaneous left ventricular assist in the electrophysiology laboratory. J Cardiovasc Electrophysiol 18: 106–109, 2007. 22. Foo D, Walker BD, Kuchar DL, et al: Left ventricular mechanical assist devices and cardiac device interactions: An observational case series. Pacing Clin Electrophysiol 32: 879–887, 2009. 23. Ambardekar AV, Lowery CM, Allen LA, et al: Effect of left ventricular assist device placement on preexisting implantable cardioverter-defibrillator leads. J Card Fail 16: 327–331, 2010.
Clinical Cardiovascular
Catheter Ablation for Ventricular Tachyarrhythmias in Patients Supported by Continuous-Flow Left Ventricular Assist Devices Arthur R. Garan,* Vivek Iyer,* William Whang,* Kanika P. Mody,* Melana Yuzefpolskaya,* Paolo C. Colombo,* Rosie Te-Frey,† Hiroo Takayama,† Yoshifumi Naka,† Hasan Garan,* Ulrich P. Jorde,* and Nir Uriel*
Ventricular arrhythmias (VAs) are common after implantation of a left ventricular assist device (LVAD) and in a subset of patients may be refractory to medication. Morbidity from VA in this population includes right ventricular failure (RVF). We sought to evaluate the efficacy of catheter ablation for VA in patients with LVAD. A retrospective analysis of patients supported by continuous-flow LVAD referred for catheter ablation of ventricular tachycardia (VT) between 2008 and the present was performed. Seven patients were referred for VT ablation an average of 236 ± 292 days after LVAD implantation. Three patients (42.9%) developed RVF in the setting of intractable arrhythmias. A transfemoral approach was used for six patients (85.7%) and an epicardial for one patient (14.3%). The clinical VT was inducible and successfully ablated in six patients (85.7%). The location of these arrhythmias was apical in three cases (42.9%). A total of 13 VTs were ablated in seven patients. Although the majority had reduction in VA frequency, recurrent VAs were observed in six patients (85.7%). One patient (14.3%) experienced a bleeding complication after the procedure. For patients with a high VA burden after LVAD implantation, VT ablation is safe and feasible, but VA frequently recurs. ASAIO Journal 2014; 60:311–316.
respect to both survival and quality of life.1 Furthermore, advances in mechanical circulatory support technology have further improved long-term outcomes in this patient population.2,3 Continuous-flow left ventricular assist devices (CF-LVAD) have supplanted the older, pulsatile-flow pumps. As more patients undergo implantation of a long-term CF-LVAD, new dilemmas in clinical management have been identified. One problem frequently encountered in patients supported by CF-LVAD is ventricular arrhythmia (VA). We have previously shown that although VAs are common in patients supported by CF-LVAD, they are also well tolerated acutely in this population.4 However, recurrent, intractable VA can result in frequent ICD therapies which carry significant morbidity. Furthermore, intractable VA may also result in hemodynamic compromise despite CF-LVAD presence because of worsening right ventricular failure. In the case of frequent, intractable VA despite antiarrhythmic therapy in patients supported by CF-LVAD, catheter ablation of the ventricular tachycardia (VT) remains an option for management. Several centers have reported success with this procedure to reduce the frequency of such arrhythmias, although there remain relatively little data to guide the management decisions with this clinical scenario.5–9 Methods
Key Words: left ventricular assist device, ventricular tachycardia, ablation
We retrospectively reviewed charts of patients who had undergone implantation of a long-term CF-LVAD between January 1, 2008 and December 31, 2012. We identified those who had undergone electrophysiology study and catheter ablation for VT after CF-LVAD implantation. Demographic information and clinical information including ventricular dimensions, medications, and electrophysiologic parameters were recorded. In addition, details of the procedure were obtained. Ventricular arrhythmia was defined as any of the following: any ventricular tachyarrhythmia (VT or ventricular fibrillation [VF]) that received appropriate therapy (antitachycardia pacing [ATP] or shock) from an ICD or was sustained for greater than 30 seconds in the absence of effective treatment. VT storm was defined as any of the following: three or more appropriate tachytherapies or two or more episodes of stable VT without tachytherapy in a 24 hour period, or VT occurring immediately after termination, or sustained and nonsustained VT resulting in a total number of ventricular ectopic beats greater than sinus beats in a 24 hour period. Right ventricular failure was defined by the need for right ventricular assist device placement, prolonged pulmonary vasodilators, or prolonged inotrope use.
In patients with advanced heart failure, left ventricular assist devices (LVADs) have demonstrated significant benefits with
From the *Department of Medicine, Division of Cardiology, Columbia University Medical Center, New York, New York; and †Department of Surgery, Division of Cardiothoracic Surgery, Columbia University Medical Center, New York, New York. Submitted for consideration October 21, 2013; accepted for publication in revised form February 3, 2014. Ulrich P. Jorde contributed equally as senior author. Disclosure: Dr. Naka is a consultant for Terumo Heart Inc., Thoratec Corp., and Cardio-MEMS. Dr. Jorde has received consulting fees from Thoratec Corp. Dr. Uriel has received consulting fees from Heartware, Inc. The other authors have no conflicts of interest to report. Reprint Requests: Nir Uriel, MD, Mechanical Circulatory Support Program, Division of Cardiology, Columbia University Medical Center–New York-Presbyterian Hospital, 622 West 168th Street, PH-12, Room 134, New York, NY 10032. Email: [email protected], [email protected]. Copyright © 2014 by the American Society for Artificial Internal Organs DOI: 10.1097/MAT.0000000000000061
311
312 GARAN et al. Table 1. Baseline Demographics of Patients Undergoing VTA Patient 1 2 3 4 5 6 7
Age (Years)
Sex
Cardiomyopathy
LVAD Indication
VTA Indication
Days After LVAD Implantation
76 50 52 75 66 62 74
M M M M M M M
Ischemic Nonischemic Nonischemic Ischemic Ischemic Ischemic Ischemic
DT BTT BTT DT BTT BTT DT
Recurrent ICD firing RV failure Recurrent ICD firing Recurrent ICD firing Recurrent ICD firing RV failure RV failure
24 8 55 453 177 133 802
BTT, bridge-to-transplant; DT, destination therapy; LVAD, left ventricular assist device; M, male; RV, right ventricle; VTA, ventricular tachycardia ablation.
Electrophysiology study and VT ablation (VTA) were performed at our institution. The patient’s ICD was reprogramed to deactivate tachycardia therapies at the beginning of each case. However, the level of hemodynamic support was not changed periprocedurally (i.e., no LVAD reprograming was performed and no mechanical right ventricular support was used). For cases in which presenting rhythm was not VT, induction using programmed stimulation with up to triple extrastimuli was performed from the right ventricle; if VT was noninducible, a second site was generally used. Only monomorphic VTs were targeted, including the clinical VT (if clinical morphology was known or was the presenting rhythm); cardioversion was performed for induced sustained polymorphic VT or VF. Left ventricular access was obtained either via retrograde aortic or transseptal approach with femoral vascular access or via sternotomy if epicardial access was required. Mapping was performed during monomorphic VTs with stable hemodynamics in all cases, using CARTO (Biosense Webster, Diamond Bar, CA) or EnSite NavX (St. Jude Medical, St. Paul, MN) electroanatomic mapping systems. An entrainment or activation mapping strategy during VT was preferred.10 A pure substrate-based approach was elected in cases where VT was inducible. An irrigated 3.5 mm radiofrequency (RF) catheter was used for mapping and lesion delivery (Thermocool SF; Biosense Webster) using power delivery of up to 40 Watts. The procedure concluded at the operator’s discretion after 1) acute termination of the clinically observed VT during RF delivery (or RF delivery at a site where mechanical termination occurred), followed by substrate modification at adjacent sites within the scar, 2) targeting of additional induced monomorphic VTs, or 3) noninducibility of sustained monomorphic VTs with the programmed stimulation protocol.
Results Patient Characteristics Of 224 patients who underwent implantation of a long-term CF-LVAD between January 1, 2008 and December 31, 2012, we identified seven patients (3.1%) who had undergone electrophysiology study and VTA while on CF-LVAD support. Currently at our institution, 23% of CF-LVAD recipients experience at least one VA postoperatively and 4% experience five or more. Patients underwent VTA on average 236 ± 292 days after CF-LVAD implantation. The average age of the patients was 65.0 ± 10.8 years and all (100%) were men (Table 1). Five (71.4%) of the seven patients had an ischemic cardiomyopathy and four (57.1%) had undergone CF-LVAD implantation as a bridge-to-transplant (BTT). The average left ventricular end-diastolic dimension (LVEDd) was 6.6 ± 0.7 cm. All patients (100%) had experienced at least one VA preoperatively, although only one patient (14.3%) had undergone VTA. Five patients (71.4%) had experienced VT storm before CF-LVAD implantation and four of these patients experienced VT storm within 1 week before surgery. At the time of VTA, all patients (100%) were being treated with beta-blockers and six (85.7%) were being treated with amiodarone. In addition, five (71.4%) were receiving either mexilitene or lidocaine and two (28.6%) were receiving other antiarrhythmic medications (quinidine for one patient and propafenone for another patient; Table 2). The indication for VTA was recurrent ICD firings in four patients (57.1%) and right heart failure caused by refractory arrhythmia in three patients (42.9%). All three patients whose indication for VTA was RV failure had perioperative RV failure and two of the four patients whose indication was recurrent ICD firing had perioperative RV failure. Of those with right
Table 2. Electrophysiologic History of Patients Undergoing VTA Patient 1 2 3 4 5 6 7
Beta-Blocker
Amiodarone
Mexilitene, Lidocaine
Other AAD
VA Pre-LVAD
VT Storm Pre-LVAD
VTA Pre-LVAD
CRT-D
Yes Yes Yes Yes Yes Yes Yes
Yes Yes Yes Yes Yes Yes No
No Yes Yes Yes Yes No Yes
No Propafenone Quinidine No No No No
Yes Yes Yes Yes Yes Yes Yes
Yes Yes Yes No Yes Yes No
No Yes No No No No No
Yes Yes Yes Yes Yes Yes Yes
AAD, antiarrhythmic drug; CRT-D, cardiac resynchronization therapy-defibrillator; LVAD, left ventricular assist device; VA, ventricular arrhythmia; VT, ventricular tachycardia; VTA, ventricular tachycardia ablation.
313
15.5 Acute termination with RFA During VT Inferior/apical 7
1, 1
Lateral/apical Inferior/basal 5 6
LVAD, left ventricular assist device; OHT, orthotopic heart transplant; RFA, radiofrequency ablation; SR, sinus rhythm; VA, ventricular arrhythmia; V pacing, ventricular pacing; VT, ventricular tachycardia.
Alive on LVAD support Less frequent No
No Yes
None Groin hematoma, difficult defibrillation None Not obtained Not obtained Acute termination with RFA Acute termination with RFA During VT During VT
Inferior/mid 4
1, 1 1, 1
During VT
Lateral/basal 3
4, 4
During VT
Lateral/apical 2
5, 1
Inferior/basal 1
6, 4
Less frequent Less frequent
Expired on LVAD support Bridged to OHT Bridged to OHT Less frequent Yes None 25
No change Yes None 36
No change Yes None 13
RFA at site of mechanical termination RFA at site of mechanical termination Acute termination with RFA
Less frequent Yes None 38 Clinical VA not inducible
During SR/ V pacing During VT
Recurrent VA Complications Fluoro Time (min) Mode of Termination Mapping Performed VA Induced, Ablated
The average time on CF-LVAD support after VTA was 149 ± 108 days. Five patients (71.4%) had reduction in the burden of VA after the VTA. Of these patients, one (14.3%) was without VA entirely until orthotopic heart transplant (OHT), whereas four (57.1%) had at least one recurrent VA. Two patients (28.6%) who had ablation of the clinical arrhythmia continued to have VA after the procedure without reduction in the VA burden despite acute success of the VTA. Three patients (42.9%) expired on LVAD support; of these, one had undergone LVAD implantation as BTT and the other two patients as destination therapy (DT). The causes of death included right ventricular failure leading to multi-organ failure in two patients and device-related death in another. One patient (14.3%) remains on LVAD support as DT. Three patients (42.9%) were successfully bridged to OHT.
Location of Clinical VA
Outcomes
Table 3. Procedural Characteristics and Clinical Outcomes
Five (71.4%) of the procedures were performed via retrograde aortic approach, whereas one (14.3%) was performed via transseptal approach and one (14.3%) via an epicardial approach requiring re-operative median sternotomy 8 days after LVAD implantation. An epicardial approach was used in this case because the patient had undergone VTA before LVAD implantation and was felt to have a substantial burden of epicardial VT substrate. Six patients (85.7%) underwent entrainment or activation mapping during VT, whereas a pure substrate-based strategy was used in one (14.3%) case (Table 3). Intravenous heparin was the procedural anticoagulation strategy in all patients (100%); in addition, five patients (71.4%) were also within the therapeutic range of warfarin. The procedure was performed with general anesthesia in two patients (28.6%) and moderate sedation in five patients (71.4%). A total of 19 VTs were induced and 13 were ablated. In six (85.7%) of the procedures, the clinical VT was inducible or present at the time of ablation. Examples of clinical tachycardias are presented in figure 1. The foci of the clinical tachycardias were left ventricular: lateral/apical in two patients (28.6%), inferior/basal in two (28.6%), inferior/apical in one (14.3%), lateral/basal in one (14.3%), and inferior/mid-ventricular in one (14.3%). Two of three patients with VT localized to the apical region and two of four patients with VT localized to other areas of the myocardium had evidence of migration of the inflow cannula position on chest X-ray between the time of implant and the time of VTA. In four instances, the procedure was terminated after acute termination of the clinical arrhythmia occurred during RF delivery; in two instances, the procedure concluded after termination of the clinical arrhythmia and targeting of multiple other inducible monomorphic tachycardias; and in one instance, the procedure was terminated after the clinical arrhythmia could no longer be induced after RF delivery.
Effect on VA Frequency
Procedural Characteristics
1, 1
Long-Term Outcome
heart failure as the indication, one patient required right ventricular assist device placement and two were treated with pulmonary vasodilators for a prolonged period of time. The right ventricular assist device was placed 5 days after VTA which, despite achieving acute success, did not resolve the right ventricular failure. The patient remained on biventricular support until the time of transplant.
Expired on LVAD support Expired on LVAD support Bridged to OHT
CATHETER ABLATION FOR VT
Patient
314 GARAN et al.
Figure 1. Examples of clinical ventricular tachycardia for patients referred for catheter ablation. A and B: These 12 lead ECGs were obtained from patients who underwent successful ablation of the arrhythmias while on continuous-flow left ventricular assist device support. The ECG in (B) represents a tachycardia which was localized to the apical region of the left ventricle.
Safety There were no intraprocedural complications during VTA. In one instance (14.3%), there was difficulty in defibrillating the patient resulting in prolonged periods of VF. Defibrillation required two sets of defibrillator pads. This patient ultimately tolerated the procedure and the prolonged period of VF well. No patients sustained damage to the ventricular assist device or its connection to the myocardium even when the procedure was performed as few as 8 days after CF-LVAD implantation. One patient (14.3%) developed a groin hematoma which required transfusion of 2 units of packed red blood cells. No patients had worsening renal function after the procedure. Finally, no patients died during or within the 30 days after the procedure. Discussion Herein, we present a series of seven patients supported with long-term CF-LVAD with recurrent VA affecting the quality of life and morbidity of the patients. Indications for VTA were recurrent, appropriate ICD firing despite medical therapy and right heart failure as a result of intractable VA. Our data indicate that catheter ablation of VT may be performed safely via retrograde or epicardial approach with modest efficacy in reducing the burden of VA while on CF-LVAD support.
Although VAs after CF-LVAD implantation are common,4,11–18 only 3.1% of CF-LVAD recipients at our center had such significant burden of VA that VTA was undertaken. These results are similar to those reported by multiple centers,5,6 although our data include exclusively patients with continuous-flow pumps. Whether different pumps (i.e., pulsatile vs. different continuous-flow designs) have different effects on the inci dence and significance of VA is unknown. All of the patients who underwent VTA while on long-term CF-LVAD support had at least one VA before surgery, but only one had undergone VTA preoperatively. Interestingly, a history of VT storm was common among our cohort, a finding also noted by Herweg et al.5 Furthermore, the majority of our patients had experienced VT storm in the week before surgery. This suggests that patients whose need for mechanical circulatory support is largely due to electrical instability remain at risk for significant arrhythmias that require further advanced treatment strategies postoperatively. Our data are novel in that they highlight one of the morbidities associated with intractable VA: right ventricular failure. Almost half of our patients were referred for VTA because of right ventricular failure which can occur even with slower VAs when they become intractable. Whether patients with right ventricular failure attributable to intractable arrhythmias fare as well as patients without this complication after has not been
315
CATHETER ABLATION FOR VT
previously studied. In our series, all patients with right ventricular failure had recurrence of VA after the procedure and one continued to have VA at the same frequency as had been experienced preprocedurally. Importantly, two complications were noted: both postprocedural bleeding and difficulty with defibrillation during the procedure occurred in our series. However, neither complication resulted in permanent morbidity or mortality. Bleeding complications in this patient population remain a concern given the need for anticoagulation and the acquired von-Willebrand syndrome observed after device implantation.19 One patient could not easily be defibrillated after the initiation of ventricular fibrillation with programmed stimulation. Multiple shocks were unsuccessful at restoring sinus rhythm, and it was only when two sets of pads were used that VF was terminated. It is worthwhile to note that this prolonged arrhythmia did not result in hemodynamic collapse, highlighting one potential advantage to undertaking VTA in patients with a CF-LVAD. Indeed, percutaneous temporary mechanical support has been used more frequently to facilitate VTA.20,21 Although this difficulty is not limited to patients with CF-LVAD, this observation raises a question about the effects of CF-LVAD implantation on the defibrillation threshold (DFT). Although multiple centers have reported increases in sensing and stimulation threshold after LVAD implantation, currently no data exist regarding the effects on DFT.22,23 Overall, VTA was acutely successful in the majority of cases. Most patients had ablation of the clinical VT, and the majority had a reduction in the frequency of their VA after the procedure. However, that this subset of patients was particularly prone to VA after CF-LVAD implantation is underscored by the fact that even after successful ablation, VAs still recurred in the majority of patients. Although the rate of acute ablative success in our series is similar to those in other published reports, the rate of recurrence appears higher.5,6 There may be multiple reasons for this. One possible reason is that time on support after VTA was longer in our series than that in other published reports. Second, it is also possible that closer surveillance allowed us to detect arrhythmias that would have otherwise gone undetected, such as successful ATP events. Some of the patients in our study were enrolled in a prospective study quantifying VA in patients with LVAD and frequent surveillance was performed even in the absence of clinically recognized arrhythmias. Finally, it is possible that our patients had a greater burden of arrhythmias with more arrhythmia substrate or more triggers such as right heart failure. Whether recurrent VAs included those that were induced but not ablated during the procedure is unknown. It is also of interest that the origin of the clinical VA was apical—possibly related to the inflow cannula—in about one half of patients, a finding that differs from previously published reports which included earlier generation pumps.11 Last, the time course of the clinically significant arrhythmias post-LVAD is of interest. Although the presence of preoperative VA is known to be the strongest predictor of postoperative VA,4 the timing of these events is less predictable. Although some patients had a heavy burden of VA in the immediate postoperative period requiring VTA, others developed a significant burden of VA requiring the procedure more than 2 years after surgery.
Limitations The retrospective nature of our study limited our ability to detect all VAs for each patient, making it difficult to quantify the magnitude of the effect of the procedure on VAs. Furthermore, device settings were not standardized so that patients with more aggressive settings might have inflation of the number of VAs experienced if their ICD device was delivering tachytherapies for slower or shorter VA. Last, these data represent a single-center experience in small cohort of patients; whether our findings can be applied to the general population of patients with CF-LVAD is unknown. Conclusions Although VAs are common after CF-LVAD implantation, a small subset of patients has refractory VA requiring more advanced antiarrhythmic therapies. Although these arrhythmias are well tolerated acutely, they are not without morbidity which includes right ventricular failure. For such patients, endo- or epicardial ablation of the VA may be safely performed when medical therapy is insufficient to control the arrhythmia burden. However, despite acute success of this procedure, VA frequently recurs. References 1. Rose EA, Gelijns AC, Moskowitz AJ, et al; Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure (REMATCH) Study Group: Long-term use of a left ventricular assist device for end-stage heart failure. N Engl J Med 345: 1435–1443, 2001. 2. Slaughter MS, Rogers JG, Milano CA, et al; HeartMate II Investigators: Advanced heart failure treated with c ontinuous-flow left ventricular assist device. N Engl J Med 361: 2241–2251, 2009. 3. Garatti A, Bruschi G, Colombo T, et al: Clinical outcome and bridge to transplant rate of left ventricular assist device recipient patients: Comparison between continuous-flow and pulsatileflow devices. Eur J Cardiothorac Surg 34: 275–280, 2008. 4. Garan AR, Yuzefpolskaya M, Colombo PC, et al: Ventricular arrhythmias and implantable cardioverter-defibrillator therapy in patients with continuous-flow left ventricular assist devices: Need for primary prevention? J Am Coll Cardiol 61: 2542–2550, 2013. 5. Herweg B, Ilercil A, Kristof-Kuteyeva O, et al: Clinical observations and outcome of ventricular tachycardia ablation in patients with left ventricular assist devices. Pacing Clin Electrophysiol 35: 1377–1383, 2012. 6. Cantillon DJ, Bianco C, Wazni OM, et al: Electrophysiologic characteristics and catheter ablation of ventricular tachyarrhythmias among patients with heart failure on ventricular assist device support. Heart Rhythm 9: 859–864, 2012. 7. Osaki S, Alberte C, Murray MA, et al: Successful radiofrequency ablation therapy for intractable ventricular tachycardia with a ventricular assist device. J Heart Lung Transplant 27: 353–356, 2008. 8. Dandamudi G, Ghumman WS, Das MK, Miller JM: Endocardial catheter ablation of ventricular tachycardia in patients with ventricular assist devices. Heart Rhythm 4: 1165–1169, 2007. 9. Emaminia A, Nagji AS, Ailawadi G, Bergin JD, Kern JA: Concomitant left ventricular assist device placement and cryoablation for treatment of ventricular tachyarrhythmias associated with heart failure. Ann Thorac Surg 92: 334–336, 2011. 10. Stevenson WG, Khan H, Sager P, et al: Identification of reentry circuit sites during catheter mapping and radiofrequency ablation of ventricular tachycardia late after myocardial infarction. Circulation 88(4 Pt 1): 1647–1670, 1993.
316 GARAN et al. 11. Ziv O, Dizon J, Thosani A, Naka Y, Magnano AR, Garan H: Effects of left ventricular assist device therapy on ventricular arrhythmias. J Am Coll Cardiol 45: 1428–1434, 2005. 12. Refaat M, Chemaly E, Lebeche D, Gwathmey JK, Hajjar RJ: Ventricular arrhythmias after left ventricular assist device implantation. Pacing Clin Electrophysiol 31: 1246–1252, 2008. 13. Cantillon DJ, Tarakji KG, Kumbhani DJ, Smedira NG, Starling RC, Wilkoff BL: Improved survival among ventricular assist device recipients with a concomitant implantable cardioverter-defibrillator. Heart Rhythm 7: 466–471, 2010. 14. Refaat MM, Tanaka T, Kormos RL, et al: Survival benefit of implantable cardioverter-defibrillators in left ventricular assist device-supported heart failure patients. J Card Fail 18: 140– 145, 2012. 15. Oswald H, Schultz-Wildelau C, Gardiwal A, et al: Implantable defibrillator therapy for ventricular tachyarrhythmia in left ventricular assist device patients. Eur J Heart Fail 12: 593–599, 2010. 16. Bedi M, Kormos R, Winowich S, McNamara DM, Mathier MA, Murali S: Ventricular arrhythmias during left ventricular assist device support. Am J Cardiol 99: 1151–1153, 2007. 17. Andersen M, Videbaek R, Boesgaard S, Sander K, Hansen PB, Gustafsson F: Incidence of ventricular arrhythmias in patients on long-term support with a continuous-flow assist device (HeartMate II). J Heart Lung Transplant 28: 733–735, 2009.
18. Ambardekar AV, Allen LA, Lindenfeld J, et al: Implantable cardioverter-defibrillator shocks in patients with a left ventricular assist device. J Heart Lung Transplant 29: 771–776, 2010. 19. Uriel N, Pak SW, Jorde UP, et al: Acquired von Willebrand syndrome after continuous-flow mechanical device support contributes to a high prevalence of bleeding during long-term support and at the time of transplantation. J Am Coll Cardiol 56: 1207–1213, 2010. 20. Abuissa H, Roshan J, Lim B, Asirvatham SJ: Use of the Impella microaxial blood pump for ablation of hemodynamically unstable ventricular tachycardia. J Cardiovasc Electrophysiol 21: 458–461, 2010. 21. Friedman PA, Munger TM, Torres N, Rihal C: Percutaneous endocardial and epicardial ablation of hypotensive ventricular tachycardia with percutaneous left ventricular assist in the electrophysiology laboratory. J Cardiovasc Electrophysiol 18: 106–109, 2007. 22. Foo D, Walker BD, Kuchar DL, et al: Left ventricular mechanical assist devices and cardiac device interactions: An observational case series. Pacing Clin Electrophysiol 32: 879–887, 2009. 23. Ambardekar AV, Lowery CM, Allen LA, et al: Effect of left ventricular assist device placement on preexisting implantable cardioverter-defibrillator leads. J Card Fail 16: 327–331, 2010.
