In patients with advanced heart failure, left ventricular assist devices (LVADs) have demonstrated significant benefits with 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
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.
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.
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 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.
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.
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.
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.
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 incidence 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 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.
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.
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.
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