Role of Cardiac Resynchronization Therapy in Patients with Left Ventricular Assist Support

To the Editors: Both cardiac resynchronization therapy (CRT) and left ventricular assist device (LVAD) therapy, in isolation, improve survival, functional capacity, and promote reverse cardiac remodeling in patients with systolic heart failure (HF). The combined impact of these two devices in HF patients remains unclear. Thus, we read with great interest the study by Tehrani et al.1 on the impact of CRT on LV unloading in patients receiving LVAD support. The investigators observed that CRT does not provide additional LV unloading in the presence of an LVAD. Additionally, they advocate inactivation of CRT in HF patients on LVAD support. To understand the acute effect of CRT on hemodynamics and LV unloading, comparison should be made before and after inactivating CRT in the same patient, thus the patient acts as their own control. In addition, CRT might have impact on right ventricular (RV) reserve beyond resting RV function2 which can only be unmasked during exercise or hemodynamic stress.3 Apart from acute changes, turning CRT off might affect long-term RV function which could be crucial for successful LVAD therapy.3 The data on CRT in LVAD patients in regards to increased ventricular arrhythmias are inconclusive4–6 and warrant further investigation. Long-term CRT facilitates myocardial remodeling independent of electrical and mechanical synchrony by modulating overactive sympathetic tone.7 Whether these CRT benefits hold true in patients with LVAD support and add to myocardial recovery beyond immediate hemodynamic effect remain undetermined and call for further study. In fact, lower myocardial recovery rate while on LVAD support has been attributed to lack of or suboptimal use of HF therapy as well as lack of prespecified myocardial recovery assessment.8 Importantly, CRT management in LVAD patients varies between centers resulting in variable conclusions. Systematic multicenter undertakings are needed to ascertain the additive role of CRT in patients with LVAD support exploring long-term hemodynamic effects, role in myocardial recovery, and risk for ventricular arrhythmias along with impact on functional capacity. Nirav PatelJason GluckAbhishek JaiswalDivision of CardiologyAdvanced Heart Failure and Transplant CenterHartford Hospital/University of ConnecticutHartford, Connecticut