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Incidence of Ventricular Arrhythmias in Patients on Long-term Support With a Continuous-flow Assist Device (HeartMate II)
CLINICAL DILEMMAS AND INNOVATION
Incidence of Ventricular Arrhythmias in Patients on Long-term Support With a Continuous-flow Assist Device (HeartMate II) Mads Andersen, MD,a Regitze Videbæk, MD,a Søren Boesgaard, MD,a Kåre Sander, MD,b Peter B. Hansen, MD,c and Finn Gustafsson, MDa The incidence of ventricular tachycardia (VT) or ventricular fibrillation (VF) in patients supported with a continuous-flow left ventricular assist device (LVAD) has not been investigated in detail. In 23 consecutive recipients of a HeartMate II, we analyzed the incidence of VT/VF during a total of 266 months of follow-up. Sustained VT or VF occurred in 52% of the patients, with the majority of arrhythmias occurring in the first 4 weeks after LVAD implantation. VT/VF requiring implantable cardioverter-defibrillator (ICD) shock or external defibrillation occurred in 8 patients and significant hemodynamic instability ensued in 3 patients. There were no clear predictors of VT/VF, and it is argued that prophylactic ICD implantation should be considered in patients supported with a continuous-flow LVAD. J Heart Lung Transplant 2009;28:733–5. Copyright © 2009 by the International Society for Heart and Lung Transplantation.
Ventricular arrhythmias are common in patients supported with a left ventricular assist device (LVAD).1,2 The pathogenesis is related to the presence of an arrhythmogenic substrate associated with the underlying cardiomyopathy as well as to scar tissue associated with the left ventricular outflow cannula.1 The vast majority of data on arrhythmic burden in LVAD patients have been generated from studies of patients supported with a pulsatile LVAD and included mainly short-term post-operative follow-up. Recently, continuous-flow assist devices have gained increasing popularity.3,4 It is unknown whether the risk of ventricular arrhythmia with this type of pump is comparable to that seen with pulsatile devices. In theory, continuous-flow devices would be associated with a higher risk of ventricular tachycardia (VT) or ventricular fibrillation (VF) because of the potential for arrhythmia developing during left ventricular suction episodes.5 Furthermore, the clinical consequences of ventricular arrhythmias are unclear in this population. Our purpose was to assess the incidence and clinical consequences of VT and VF during short- and long-term support in patients with a continuous-flow LVAD, specifically the HeartMate II (HMII).
From the Departments of aCardiology, bCardiothoracic Surgery and c Cardiothoracic Anesthesia, The Heart Centre, Rigshospitalet, Copenhagen, Denmark. Submitted December 3, 2008; revised January 31, 2009; accepted March 5, 2009. Reprint requests: Mads Andersen, MD, Department of Cardiology B, Rigshospitalet 2141, 9 Blegdamsvej, 2100 Copenhagen, Denmark. Telephone: ⫹45-24417760. Fax: ⫹45-35452513. E-mail: [email protected] Copyright © 2009 by the International Society for Heart and Lung Transplantation. 1053-2498/09/$–see front matter. doi:10.1016/ j.healun.2009.03.011
METHODS Subjects We reviewed the hospital records of 23 consecutive recipients of a HMII (Thoratec, Pleasanton, CA) who were implanted at Rigshospitalet, Copenhagen, from March 2006 to July 2008. The mean duration of support was 341 days (range 6 to 802 days). Patient charts and implantable cardioverter-defibrillator (ICD) memory interrogation reports were reviewed. Indications for device implantation included bridge to transplantation in 19 patients and destination therapy in 4 patients. Baseline characteristics are presented in Table 1. An implantable defibrillator was in place in 17 (74%) of the patients. Ten of the ICDs were implanted after the LVAD as part of an evolving strategy at our institution to offer all ambulatory patients on HMII support a prophylactic defibrillator. Total follow-up time on HMII support where patients had an ICD in place was 214 months, whereas follow-up time without an ICD was 52 months. The 6 non-ICD patients accounted for 42 of the 52 months and delay from HMII surgery until ICD implantation accounted for the remaining 10 months. No patient received a St. Jude Atlas (V-193) ICD, which has been reported to malfunction in patients with HMIIs.6 One patient, without an ICD, died from multiple-organ failure 30 days after HMII implantation, whereas the remaining 22 (96%) are alive. Ten of the 19 bridge-to-transplant patients have been transplanted and 8 are still awaiting transplantation. Total follow-up time on HMII support was 266 months. Ventricular Arrhythmia Analysis Sustained VT was defined as VT lasting ⬎30 seconds. Arrhythmia was detected by electrocardiographic (ECG) monitoring during the in-hospital period, by ICD inter733
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The Journal of Heart and Lung Transplantation July 2009
remaining 22% did not tolerate -blockade. No patient was treated with clenbuterol.
Table 1. Data for Patients With and Without Ventricular Tachycardia/Ventricular Fibrillation (VT/VF) Characteristics Age/years (SD) Male Dilated cardiomyopathy Ischemic heart disease Patients with ICD implanted prior to VAD Patients with VT/VF prior to VAD HMII support duration/days (range) Time with ICD after HMII implant/days (range) Time without ICD after HMII implant/days (range) RV failurea Beta-blockers Amiodarone BSA/m2 (SD)
No VT/VF (n ⫽ 11) 40 (⫾15) 8 (72%) 8 (72%) 3 (27%)
VT/VF (n ⫽ 12) 45 (⫾14) 9 (75%) 6 (50%) 4 (33%)
3 (27%) 1 (9%)
3 (25%) 4 (33%)
325 (6–620)
351 (30–802)
319 (47–620)
333 (39–802)
88 (0–392) 3 (27%) 8 (72%) 10 (91%) 1.97 (⫾0.16)
49 (0–370) 5 (42%) 10 (83%) 12 (100%) 2.02 (⫾0.19)
ICD, intracoronary device; VAD, ventricular assist device; HMII, HeartMate II; BSA, body surface area. All p ⬎ 0.05. a RV failure is defined as clinical signs of HF requiring furosemide ⬎80 mg/day at ⬎1 month after HMII.
rogation 1 month after implantation, and every 6 months thereafter and by clinical evaluation and ECG or telemetry in case of suspected arrhythmic events. Episodes of sustained VT, VF and treatment (medical, anti-tachycardia pacing [ATP] or shock) were recorded. Twenty-two patients (96%) received amiodarone, which was usually continued after ICD implantation to minimize the risk of shock therapy. Eighteen patients (78%) were treated with a -blocker, but the
Statistical Analysis Proportions were compared using Fisher’s exact test. p ⬍ 0.05 was considered significant. RESULTS Five (22%) patients had sustained VT or VF before HMII implantation. After HMII implantation, 12 of the 23 patients (52%) had sustained ventricular arrhythmias that were treated either by the ICD (n ⫽ 7), required external defibrillation (n ⫽ 4, including 3 non-ICD patients and 1 ICD patient with slow VT) or resolved spontaneously (n ⫽ 1). Of the 12 patients with VT/VF, 4 had documented arrhythmia before HMII surgery and 8 had new-onset arrhythmia. Patients with ischemic heart disease (IHD) did not develop VT/VF more frequently than patients without IHD (p ⬎ 0.05). Patients treated with -blockers or amiodarone did not have a lower incidence of VT/VF (p ⬎ 0.05 for both). Of the patients who experienced ventricular arrhythmia, 9 (75%) did so within 4 weeks of the LVAD implant. Three patients had the first event at ⬎4 weeks after surgery (after 1, 9 and 13 months, respectively; Figure 1). None of the patients with arrhythmia within the first 4 weeks post-operatively died of arrhythmia or had worsening symptoms associated with the event, but in all patients with early VT/VF, the episode predicted recurrent arrhythmic events. In only 1 patient was LVAD suction the suspected origin of the sustained ventricular arrhythmia. Several patients had suctioninduced non-sustained VT during echocardiographyguided adjustment of the HMII rotor speed, but these
Figure 1. Number of patients with appropriate ICD shocks or receiving external defibrillation (gray bars) and number of patients with sustained VT resolving spontaneously or undergoing treatment with anti-tachycardia pacing (black bars) according to time from HMII implantation. Some patients had events on multiple occasions and are therefore depicted in the figure more than once.
The Journal of Heart and Lung Transplantation Volume 28, Number 7
arrhythmias did not evolve into sustained VT after the rotor speed was adjusted to relieve suction. These arrhythmias were not recorded as VT/VF in the current study. In 1 patient, who required high doses of diuretics because of RV failure, VT was likely caused by hypokalemia. Eight patients had 23 VT/VF episodes that were terminated by either cardioversion by the ICD unit (n ⫽ 4) or external defibrillation (n ⫽ 4). Inappropriate ICD shock was delivered in 1 patient (6%). Half of the VT/VF patients’ VT episodes were terminated by ATP. In 1 patient, an episode of VT storm required radio-frequency ablation of a tachycardia originating in the LV apex. In 2 of 12 (17%) patients, VT/VF was correctly detected and treated by the ICD without the patients having any symptoms. Most patients tolerated VT/VF well. Only 3 patients had significant hemodynamic compromise during arrhythmia. One of these patients had advanced right ventricular failure prior to the arrhythmic event. Of the 3 symptomatic patients only 1 had RV failure. DISCUSSION The study shows that VT/VF is common in patients supported with a continuous-flow LVAD, especially in the early post-operative period. In fact, half of the patients had ventricular arrhythmias requiring treatment. Although most episodes were symptomatic they were generally well tolerated. We observed no deaths due to ventricular arrhythmia. There is a paucity of data on VT/VF in patients supported with a continuous-flow LVAD. In the HMII bridge-to-transplant approval study, 32 of the 133 patients (24%) required post-operative cardioversion or defibrillation. This incidence is lower than the total VT/VF incidence seen in our cohort, but corresponds reasonably well to the 32% requiring cardioversion or defibrillation in our cohort. The incidence of VT/VF in our population is comparable to the VT/VF incidence in patients with pulsatile VADs reported in some previous studies,1,2 but higher than reported in another recent study.7 A similar incidence of VT/VF in patients on continuous-flow and pulsatile VADs would suggest that suction is not a major cause of VT/VF and that the risk of arrhythmia is more likely related to the underlying cardiac disorder and the presence of an LV inflow cannula. Treatment with amiodarone or -blockers did not prevent VT/VF in our study, but may have reduced the incidence in some patients. Indeed, non-use of -blockers was a significant predictor of VT/VF in a recent study of 42 LVAD patients.8 Despite the absence of a clearly protective effect of -blocker therapy on VT/VF in our cohort, it seems reasonable to attempt aggressive -blocker up-titration in all LVAD patients, not just to
Andersen et al.
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prevent VT/VF but also to increase the likelihood of LV recovery.9 Previous studies have identified IHD as a risk factor for VT/VF in VAD patients.2 We did not observe such an association, but the number of patients with IHD in our cohort was low and, consequently, the study did not have the power to rule out an effect. There is no consensus regarding the indication for ICD implantation in continuous-flow LVAD patients. In patients with an ICD implanted already prior to VAD surgery the device should be activated after LVAD surgery.7 The question remains whether prophylactic ICD should be offered to all ambulatory patients supported with a continuous-flow LVAD. Given the high incidence of symptomatic ventricular arrhythmias seen in our population, together with the fact that some patients do undergo episodes of hemodynamic instability and the lack of clear predictors of freedom from VT/VF, we believe that a prophylactic ICD should be considered in all ambulatory patients expected to be supported by a continuous-flow LVAD for a longer period of time. However, given the nature of the current study our findings do not allow for determination of whether such a strategy is superior. Future studies in larger LVAD populations should attempt to identify new risk markers of VT/VF to optimize the anti-arrhythmic strategy in these patients. REFERENCES 1. Harding JD, Piacentino V III, Rothman S, et al. Prolonged repolarization after ventricular assist device support is associated with arrhythmias in humans with congestive heart failure. J Card Fail 2005;11:227–32. 2. Arai H, Swartz MT, Pennington DG, et al. Importance of ventricular arrhythmias in bridge patients with ventricular assist devices. ASAIO Trans 1991;37:M427– 8. 3. Miller LW, Pagani FD, Russell SD, et al. Use of a continuous-flow device in patients awaiting heart transplantation. N Engl J Med 2007;357:885–96. 4. Struber M, Sander K, Lahpor J, et al. HeartMate II left ventricular assist device; early European experience. Eur J Cardiothorac Surg 2008;34:289 –94. 5. Vollkron M, Voitl P, Ta J, et al. Suction events during left ventricular support and ventricular arrhythmias. J Heart Lung Transplant 2007;26:819 –25. 6. Rohit M, Charles JL, Sai-Sudhakar C, et al. A device– device interaction between a Thoratec HeartMate II left ventricular assist device and a St. Jude Atlas (V-193) implantable cardioverter defibrillator. J Cardiovasc Electrophysiol 2007;18:E27. 7. Bedi M, Kormos R, Winowich S, et al. Ventricular arrhythmias during left ventricular assist device support. Am J Cardiol 2007; 99:1151–3. 8. Refaat M, Chemaly E, Lebeche D, et al. Ventricular arrhythmias after left ventricular assist device implantation. Pacing Clin Electrophysiol 2008;31:1246 –52. 9. Birks EJ, Tansley PD, Hardy J, et al. Left ventricular assist device and drug therapy for the reversal of heart failure. N Engl J Med 2006;355:1873– 84.
Incidence of Ventricular Arrhythmias in Patients on Long-term Support With a Continuous-flow Assist Device (HeartMate II) Mads Andersen, MD,a Regitze Videbæk, MD,a Søren Boesgaard, MD,a Kåre Sander, MD,b Peter B. Hansen, MD,c and Finn Gustafsson, MDa The incidence of ventricular tachycardia (VT) or ventricular fibrillation (VF) in patients supported with a continuous-flow left ventricular assist device (LVAD) has not been investigated in detail. In 23 consecutive recipients of a HeartMate II, we analyzed the incidence of VT/VF during a total of 266 months of follow-up. Sustained VT or VF occurred in 52% of the patients, with the majority of arrhythmias occurring in the first 4 weeks after LVAD implantation. VT/VF requiring implantable cardioverter-defibrillator (ICD) shock or external defibrillation occurred in 8 patients and significant hemodynamic instability ensued in 3 patients. There were no clear predictors of VT/VF, and it is argued that prophylactic ICD implantation should be considered in patients supported with a continuous-flow LVAD. J Heart Lung Transplant 2009;28:733–5. Copyright © 2009 by the International Society for Heart and Lung Transplantation.
Ventricular arrhythmias are common in patients supported with a left ventricular assist device (LVAD).1,2 The pathogenesis is related to the presence of an arrhythmogenic substrate associated with the underlying cardiomyopathy as well as to scar tissue associated with the left ventricular outflow cannula.1 The vast majority of data on arrhythmic burden in LVAD patients have been generated from studies of patients supported with a pulsatile LVAD and included mainly short-term post-operative follow-up. Recently, continuous-flow assist devices have gained increasing popularity.3,4 It is unknown whether the risk of ventricular arrhythmia with this type of pump is comparable to that seen with pulsatile devices. In theory, continuous-flow devices would be associated with a higher risk of ventricular tachycardia (VT) or ventricular fibrillation (VF) because of the potential for arrhythmia developing during left ventricular suction episodes.5 Furthermore, the clinical consequences of ventricular arrhythmias are unclear in this population. Our purpose was to assess the incidence and clinical consequences of VT and VF during short- and long-term support in patients with a continuous-flow LVAD, specifically the HeartMate II (HMII).
From the Departments of aCardiology, bCardiothoracic Surgery and c Cardiothoracic Anesthesia, The Heart Centre, Rigshospitalet, Copenhagen, Denmark. Submitted December 3, 2008; revised January 31, 2009; accepted March 5, 2009. Reprint requests: Mads Andersen, MD, Department of Cardiology B, Rigshospitalet 2141, 9 Blegdamsvej, 2100 Copenhagen, Denmark. Telephone: ⫹45-24417760. Fax: ⫹45-35452513. E-mail: [email protected] Copyright © 2009 by the International Society for Heart and Lung Transplantation. 1053-2498/09/$–see front matter. doi:10.1016/ j.healun.2009.03.011
METHODS Subjects We reviewed the hospital records of 23 consecutive recipients of a HMII (Thoratec, Pleasanton, CA) who were implanted at Rigshospitalet, Copenhagen, from March 2006 to July 2008. The mean duration of support was 341 days (range 6 to 802 days). Patient charts and implantable cardioverter-defibrillator (ICD) memory interrogation reports were reviewed. Indications for device implantation included bridge to transplantation in 19 patients and destination therapy in 4 patients. Baseline characteristics are presented in Table 1. An implantable defibrillator was in place in 17 (74%) of the patients. Ten of the ICDs were implanted after the LVAD as part of an evolving strategy at our institution to offer all ambulatory patients on HMII support a prophylactic defibrillator. Total follow-up time on HMII support where patients had an ICD in place was 214 months, whereas follow-up time without an ICD was 52 months. The 6 non-ICD patients accounted for 42 of the 52 months and delay from HMII surgery until ICD implantation accounted for the remaining 10 months. No patient received a St. Jude Atlas (V-193) ICD, which has been reported to malfunction in patients with HMIIs.6 One patient, without an ICD, died from multiple-organ failure 30 days after HMII implantation, whereas the remaining 22 (96%) are alive. Ten of the 19 bridge-to-transplant patients have been transplanted and 8 are still awaiting transplantation. Total follow-up time on HMII support was 266 months. Ventricular Arrhythmia Analysis Sustained VT was defined as VT lasting ⬎30 seconds. Arrhythmia was detected by electrocardiographic (ECG) monitoring during the in-hospital period, by ICD inter733
734
Andersen et al.
The Journal of Heart and Lung Transplantation July 2009
remaining 22% did not tolerate -blockade. No patient was treated with clenbuterol.
Table 1. Data for Patients With and Without Ventricular Tachycardia/Ventricular Fibrillation (VT/VF) Characteristics Age/years (SD) Male Dilated cardiomyopathy Ischemic heart disease Patients with ICD implanted prior to VAD Patients with VT/VF prior to VAD HMII support duration/days (range) Time with ICD after HMII implant/days (range) Time without ICD after HMII implant/days (range) RV failurea Beta-blockers Amiodarone BSA/m2 (SD)
No VT/VF (n ⫽ 11) 40 (⫾15) 8 (72%) 8 (72%) 3 (27%)
VT/VF (n ⫽ 12) 45 (⫾14) 9 (75%) 6 (50%) 4 (33%)
3 (27%) 1 (9%)
3 (25%) 4 (33%)
325 (6–620)
351 (30–802)
319 (47–620)
333 (39–802)
88 (0–392) 3 (27%) 8 (72%) 10 (91%) 1.97 (⫾0.16)
49 (0–370) 5 (42%) 10 (83%) 12 (100%) 2.02 (⫾0.19)
ICD, intracoronary device; VAD, ventricular assist device; HMII, HeartMate II; BSA, body surface area. All p ⬎ 0.05. a RV failure is defined as clinical signs of HF requiring furosemide ⬎80 mg/day at ⬎1 month after HMII.
rogation 1 month after implantation, and every 6 months thereafter and by clinical evaluation and ECG or telemetry in case of suspected arrhythmic events. Episodes of sustained VT, VF and treatment (medical, anti-tachycardia pacing [ATP] or shock) were recorded. Twenty-two patients (96%) received amiodarone, which was usually continued after ICD implantation to minimize the risk of shock therapy. Eighteen patients (78%) were treated with a -blocker, but the
Statistical Analysis Proportions were compared using Fisher’s exact test. p ⬍ 0.05 was considered significant. RESULTS Five (22%) patients had sustained VT or VF before HMII implantation. After HMII implantation, 12 of the 23 patients (52%) had sustained ventricular arrhythmias that were treated either by the ICD (n ⫽ 7), required external defibrillation (n ⫽ 4, including 3 non-ICD patients and 1 ICD patient with slow VT) or resolved spontaneously (n ⫽ 1). Of the 12 patients with VT/VF, 4 had documented arrhythmia before HMII surgery and 8 had new-onset arrhythmia. Patients with ischemic heart disease (IHD) did not develop VT/VF more frequently than patients without IHD (p ⬎ 0.05). Patients treated with -blockers or amiodarone did not have a lower incidence of VT/VF (p ⬎ 0.05 for both). Of the patients who experienced ventricular arrhythmia, 9 (75%) did so within 4 weeks of the LVAD implant. Three patients had the first event at ⬎4 weeks after surgery (after 1, 9 and 13 months, respectively; Figure 1). None of the patients with arrhythmia within the first 4 weeks post-operatively died of arrhythmia or had worsening symptoms associated with the event, but in all patients with early VT/VF, the episode predicted recurrent arrhythmic events. In only 1 patient was LVAD suction the suspected origin of the sustained ventricular arrhythmia. Several patients had suctioninduced non-sustained VT during echocardiographyguided adjustment of the HMII rotor speed, but these
Figure 1. Number of patients with appropriate ICD shocks or receiving external defibrillation (gray bars) and number of patients with sustained VT resolving spontaneously or undergoing treatment with anti-tachycardia pacing (black bars) according to time from HMII implantation. Some patients had events on multiple occasions and are therefore depicted in the figure more than once.
The Journal of Heart and Lung Transplantation Volume 28, Number 7
arrhythmias did not evolve into sustained VT after the rotor speed was adjusted to relieve suction. These arrhythmias were not recorded as VT/VF in the current study. In 1 patient, who required high doses of diuretics because of RV failure, VT was likely caused by hypokalemia. Eight patients had 23 VT/VF episodes that were terminated by either cardioversion by the ICD unit (n ⫽ 4) or external defibrillation (n ⫽ 4). Inappropriate ICD shock was delivered in 1 patient (6%). Half of the VT/VF patients’ VT episodes were terminated by ATP. In 1 patient, an episode of VT storm required radio-frequency ablation of a tachycardia originating in the LV apex. In 2 of 12 (17%) patients, VT/VF was correctly detected and treated by the ICD without the patients having any symptoms. Most patients tolerated VT/VF well. Only 3 patients had significant hemodynamic compromise during arrhythmia. One of these patients had advanced right ventricular failure prior to the arrhythmic event. Of the 3 symptomatic patients only 1 had RV failure. DISCUSSION The study shows that VT/VF is common in patients supported with a continuous-flow LVAD, especially in the early post-operative period. In fact, half of the patients had ventricular arrhythmias requiring treatment. Although most episodes were symptomatic they were generally well tolerated. We observed no deaths due to ventricular arrhythmia. There is a paucity of data on VT/VF in patients supported with a continuous-flow LVAD. In the HMII bridge-to-transplant approval study, 32 of the 133 patients (24%) required post-operative cardioversion or defibrillation. This incidence is lower than the total VT/VF incidence seen in our cohort, but corresponds reasonably well to the 32% requiring cardioversion or defibrillation in our cohort. The incidence of VT/VF in our population is comparable to the VT/VF incidence in patients with pulsatile VADs reported in some previous studies,1,2 but higher than reported in another recent study.7 A similar incidence of VT/VF in patients on continuous-flow and pulsatile VADs would suggest that suction is not a major cause of VT/VF and that the risk of arrhythmia is more likely related to the underlying cardiac disorder and the presence of an LV inflow cannula. Treatment with amiodarone or -blockers did not prevent VT/VF in our study, but may have reduced the incidence in some patients. Indeed, non-use of -blockers was a significant predictor of VT/VF in a recent study of 42 LVAD patients.8 Despite the absence of a clearly protective effect of -blocker therapy on VT/VF in our cohort, it seems reasonable to attempt aggressive -blocker up-titration in all LVAD patients, not just to
Andersen et al.
735
prevent VT/VF but also to increase the likelihood of LV recovery.9 Previous studies have identified IHD as a risk factor for VT/VF in VAD patients.2 We did not observe such an association, but the number of patients with IHD in our cohort was low and, consequently, the study did not have the power to rule out an effect. There is no consensus regarding the indication for ICD implantation in continuous-flow LVAD patients. In patients with an ICD implanted already prior to VAD surgery the device should be activated after LVAD surgery.7 The question remains whether prophylactic ICD should be offered to all ambulatory patients supported with a continuous-flow LVAD. Given the high incidence of symptomatic ventricular arrhythmias seen in our population, together with the fact that some patients do undergo episodes of hemodynamic instability and the lack of clear predictors of freedom from VT/VF, we believe that a prophylactic ICD should be considered in all ambulatory patients expected to be supported by a continuous-flow LVAD for a longer period of time. However, given the nature of the current study our findings do not allow for determination of whether such a strategy is superior. Future studies in larger LVAD populations should attempt to identify new risk markers of VT/VF to optimize the anti-arrhythmic strategy in these patients. REFERENCES 1. Harding JD, Piacentino V III, Rothman S, et al. Prolonged repolarization after ventricular assist device support is associated with arrhythmias in humans with congestive heart failure. J Card Fail 2005;11:227–32. 2. Arai H, Swartz MT, Pennington DG, et al. Importance of ventricular arrhythmias in bridge patients with ventricular assist devices. ASAIO Trans 1991;37:M427– 8. 3. Miller LW, Pagani FD, Russell SD, et al. Use of a continuous-flow device in patients awaiting heart transplantation. N Engl J Med 2007;357:885–96. 4. Struber M, Sander K, Lahpor J, et al. HeartMate II left ventricular assist device; early European experience. Eur J Cardiothorac Surg 2008;34:289 –94. 5. Vollkron M, Voitl P, Ta J, et al. Suction events during left ventricular support and ventricular arrhythmias. J Heart Lung Transplant 2007;26:819 –25. 6. Rohit M, Charles JL, Sai-Sudhakar C, et al. A device– device interaction between a Thoratec HeartMate II left ventricular assist device and a St. Jude Atlas (V-193) implantable cardioverter defibrillator. J Cardiovasc Electrophysiol 2007;18:E27. 7. Bedi M, Kormos R, Winowich S, et al. Ventricular arrhythmias during left ventricular assist device support. Am J Cardiol 2007; 99:1151–3. 8. Refaat M, Chemaly E, Lebeche D, et al. Ventricular arrhythmias after left ventricular assist device implantation. Pacing Clin Electrophysiol 2008;31:1246 –52. 9. Birks EJ, Tansley PD, Hardy J, et al. Left ventricular assist device and drug therapy for the reversal of heart failure. N Engl J Med 2006;355:1873– 84.