Role of implantable cardioverter-defibrillators in patients with continuous flow ventricular assist devices.

T he management of advanced heart failure has been transformed in the past 2 decades by the advent of cardiac implantable electronic devices, such as implantable cardio-verter defibrillators (ICDs) and cardiac resynchronization therapy, and more recently the left ventricular assist device (LVAD). All 3 of these devices have been found to improve survival in patients with advanced heart failure. 1–6 Cardiac resynchronization augments cardiac output by coordinating the timing of intrinsic muscular contraction to enhance its efficiency in patients with preexisting dyssynchrony. After LVAD placement, the contribution of native LV activity may be negligible, so that continued LV pacing likely does not significantly enhance cardiac function. However, LVAD recipients remain at high risk for ventricular arrhythmias (VAs) that may adversely affect right ventricular function, preload, and cardiac output. VAs (including ventricular fibrillation) are often tolerated for prolonged time periods in LVAD recipients , permitting patients to seek medical care when symptoms are present. In this setting, the incremental survival benefit of ICDs and LVADs in combination is not clear and, indeed, controversial. Enriquez et al 7 report important data in this edition of Circulation Arrhythmia and Electrophysiology. This article is the largest study so far to examine this question in patients receiving the most commonly implanted LVAD at this time, and the only device Food and Drug Administration approved for bridge to transplant and destination therapy, the Heartmate II continuous flow device. The investigators report the clinical outcomes and survival of a cohort of 106 patients, the majority of whom received an LVAD as bridge to cardiac transplantation. Patients surviving <30 days after implant were excluded, but are refer-enced separately in the article. After LVAD implantation, 36.7% of patients did not have an active ICD. VA after LVAD implantation was common and occurred in ≈35% of patients. VAs only resulted in syncope or altered mental status in <3% of patients, although 20% had symptoms (light-headedness, palpitations, or dyspnea). These findings are important and additive to previous studies which have demonstrated the absence of a significant decrease in VA burden after LVAD implantation, 8,9 but also enhanced tolerance of VA compared with patients unsupported with a mechanical support device. The reason for tolerance of ventricular fibrillation with LVAD support in these cases likely relates to the marked reduction in pulmonary vascular resistance, which is evident in patient with chronic LVAD support. This allows for the creation of a Fontan-like circulation where …