Introduction

Numerous studies have validated the role of cardiac implantable electronic devices (CIEDs), particularly implantable cardioverter-defibrillators (ICD) and cardiac resynchronization therapy (CRT) devices, in selected heart failure (HF) patients. In the last decade, left ventricular assist devices (LVAD) have emerged as the fastest growing form of therapy for stage D HF patients. LVADs decompress the failing left ventricle (LV), by suctioning blood throw on inflow cannula located at the LV apex, and pushing it to the ascending aorta via an outflow graft. To date, there are few studies available to help guide clinical management of ICDs and CRT devices among patients who receive LVAD therapy.

Implantable Cardioverter-Defibrillators

Ventricular arrhythmias, which are often lethal in patients with advanced HF, are often well tolerated in patients with LVADs, due to a Fontan-like circulation created by the LVAD.^1-3 However, prolonged ventricular arrhythmias are deleterious to the right ventricle (RV), which is not supported by the LVAD and may be associated with near-syncope, syncope, right ventricle thrombus and progressive HF. The presence of preoperative ventricular arrhythmias is the major predictor for postoperative arrhythmia, and is associated with a 19.1 fold increased rate of postoperative ventricular arrhythmias (p<0.001) with a positive predictive value of 45.5%. The absence of preoperative ventricular arrhythmias has a negative predictive value of 96%. The first postoperative month holds a particularly high risk of ventricular arrhythmias.⁴ Ventricular arrhythmia burden is quite high following LVAD implantation, with rates of appropriate ICD tachytherapy ranging from 22 to 52%.^4-6 Retrospective observational studies, largely among those with pulsatile LVADs, have suggested a survival benefit among LVAD patients with ICDs, as well as increased rates of survival to transplantation.^7-8 In contrast, prospective studies have found that ventricular arrhythmias are rarely life threatening, and that the addition of ICD therapy does not confer a survival benefit in patients with LVADs.^9-10 Our ICD implantation practice is as describe in Figure 1.

There is a relative paucity of data regarding optimal ICD programming to treat ventricular arrhythmia in LVAD patients. The recently released 2015 HRS/EHRA/APHRS/SOLAECE Expert Consensus Statement on Optimal Implantable Cardioverter-Defibrillator Programming and Testing emphasizes relatively high rate cut-offs and extended duration of detection prior to device antitachycardia pacing (ATP) or shocks.¹¹ Notably, patients with LVADs were not included in the studies leading to those guidelines change. Traditional practice has been to intervene for secondary prevention patients with a treatment zone at approximately 10 BPM below their first VT zone. In conventional heart failure patients, there is little data to support more than two to three rounds of ATP prior to ICD shock. LVAD patients, on the other hand, can often tolerate greater rounds of ATP prior to ICD shock.¹² In the author of this article’s practice, ICDs are routinely programmed with at least two zones. A lower VT treatment zone is programmed just below the patient’s known historical VT, if known, and long duration and multiple rounds of ATP (often up to 10 rounds) prior to pursuing escalation and ICD shock. The VF zone is also programmed with a high rate cutoff (i.e., 240-250 BPM), with extended duration of detection and ATP during charging prior to ICD discharge. ICDs are usually programmed to maximum device output for first shock. Energy for successful defibrillation often increases post LVAD, and utilization of a subcutaneous array may be required, should ineffective ICD shocks be noted. The role of proactive repeat DFT testing after LVAD is an area of ongoing research.

Permanent Pacemakers

Maintenance of an adequate heart rate is necessary to preserve right-sided cardiac output and left-sided filling in patients supported with LVADs. Conduction system disease is frequently encountered in patients with stage D HF. Atrial fibrillation is often poorly tolerated following LVAD implantation, as the loss of atrial contraction and rapid ventricular rates often stress the right ventricle. Early post-operative pacing via temporary epicardial pacing wires has the added advantage of minimizing atrial fibrillation rates.¹³ In patients with complete heart block or junctional escape rhythms following LVAD implantation, increasing the pacing rate via a permanent pacemaker has been shown to improve hemodynamics and LVAD flow.^14-15 Chronotropic incompetence is extremely common among patients with advanced HF, with rates approaching 50%,¹⁶ and is even more prevalent among patients supported with LVADs with rates as high as 86% reported.¹⁷ Furthermore, the severity of chronotropic incompetence has been shown to correlate with peak VO2 performance, and the addition of rate responsive pacing can improve peak VO2.¹⁷

In the author of this article’s practice, patients receive temporary epicardial pacing leads at the time of LVAD implantation and are frequently A-V sequentially paced at a rate of 100 beats per minute immediately post-operatively to help support right ventricular cardiac output. As inotropic support is weaned, epicardial temporary pacing wires are removed, allowing for native conduction. In patients with chronotropic incompetence or high-degree atrioventricular block with bradycardia, the patients pre-existing pacemaker, or more rarely—a new pacemaker—is programmed at a rate of 80-100 beats per minute with rate responsive pacing enabled when available to maximize functional status.

Cardiac Resynchronization Therapy

Both CRT and LVAD therapy, in isolation, improve survival, functional capacity, and promote reverse remodeling of the left ventricle.^18-19 Few studies have investigated the combined impact of these two devices in the same patients; however, early case series suggest that the simultaneous use of the two technologies is not additive, and may in fact be detrimental in some patients. The addition of biventricular pacing to ICD therapy does not appear to have a mortality benefit (25.8% vs. 16.7%, p = 0.35), reduce hospitalizations (96.8% vs. 93.3%, p = 0.63), or promote further reverse remodeling (LVEDD 6.4 vs. 6.2 cm, p = 0.47) compared to ICD therapy alone.²⁰ Biventricular pacing may also increase the rates of early post-operative ventricular arrhythmias (64% vs. 4.3%, p = 0.04), and ICD shocks compared to ICD therapy alone.²¹ Perhaps counterintuitively, ventricular dysynchrony may have a theoretical advantage in patients supported with LVADs. Dysynchronous motion of the septum away from the LVAD inflow cannula may prevent dynamic obstruction of LVAD flow, analogous to techniques utilized in patients with hypertrophic obstructive cardiomyopathy.²²

In the author of this article’s practice, biventricular pacing, if previously present, is often maintained following LVAD implantation. If the ventricular arrhythmia burden is high or functional status is less than expected, a trial of right-ventricular only pacing or back up only pacing is sometimes employed. Occasionally, the authors have used real time hemodynamics during a right-heart catheterization, or real-time three-dimensional echocardiography to guide the optimal pacing mode for a given patient.

Summary and Recommendations (Figure 1)

CIED therapy in patients with LVADs requires management decisions that are tailored to the unique hemodynamics present in a continuous flow system. In the absence of profound right ventricular failure, which does poorly with sustained ventricular arrhythmia, the authors recommend a conservative tachytherapy strategy for patients with pre-existing ICDs which employs a long detection and several rounds of anti-tachycardic therapy before shock therapy. For patients without ventricular arrhythmias, the authors do not place empiric ICDs for primary prevention in anticipation of LVAD surgery. Given the poor hemodynamics with bradyarrhythmias—especially in patients with right sided dysfunction—the authors often pace patients with bradyarrhythmias or chronotropic incompetence at a moderate rate of 80 to 100 bpm with atrioventricular sequential pacing, and rate responsiveness when available. Finally, for patients with high degrees of ventricular arrhythmias, the authors will often deactivate left ventricular pacing, if CRT therapy is already in place. Although counterintuitive in the traditional HF patient, RV-LV dysynchrony may improve LVAD performance, although “tuning” of CRT systems for optimal LVAD function remains an ongoing area of research.

Figure 1: Management Tree of IED Therapy for Patients with LVAD

References

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Keywords: Aorta, Arrhythmias, Cardiac, Atrial Fibrillation, Atrioventricular Block, Bradycardia, Cardiac Catheterization, Cardiac Output, Cardiac Resynchronization Therapy, Cardiac Resynchronization Therapy, Cardiomyopathy, Hypertrophic, Familial, Defibrillators, Implantable, Echocardiography, Three-Dimensional, Heart Failure, Heart Ventricles, Heart-Assist Devices, Primary Prevention, Secondary Prevention, Thrombosis

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