Copyright © American Society of Artificial Internal Organs. Unauthorized reproduction of this article is prohibited. e42 ASAIO Journal 2019 Letter to the Editor To the Editors: Both cardiac resynchronization therapy (CRT) and left ven- tricular 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 Teh- rani 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 function 2 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 inconclusive 4–6 and warrant further investigation. Long-term CRT facilitates myo- cardial 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 Patel Jason Gluck Abhishek Jaiswal Division of Cardiology Advanced Heart Failure and Transplant Center Hartford Hospital/University of Connecticut Hartford, Connecticut References 1. Tehrani DM, Adatya S, Grinstein J, et al. Impact of cardiac resyn- chronization therapy on left ventricular unloading in patients with implanted left ventricular assist devices. ASAIO Journal. 65(2):117–122, 2019. 2. Rajagopalan N, Suffoletto MS, Tanabe M, et al: Right ventricular function following cardiac resynchronization therapy. Am J Cardiol 100: 1434–1436, 2007. 3. Valzania, C., Biffi, M., Bonfiglioli, R. et al. J. Nucl. Cardiol. (2017). https://doi.org/10.1007/s12350-017-0971-3. [Epub ahead of print]. 4. Schleifer JW, Mookadam F, Kransdorf EP, et al: Effect of continued cardiac resynchronization therapy on ventricular arrhythmias after left ventricular assist device implantation. Am J Cardiol 118: 556–559, 2016. 5. Gopinathannair R, Birks EJ, Trivedi JR, et al: Impact of cardiac resynchronization therapy on clinical outcomes in patients with continuous-flow left ventricular assist devices. J Card Fail 21: 226–232, 2015. 6. Richardson TD, Hale L, Arteaga C, et al. Prospective randomized evaluation of implantable cardioverter-defibrillator program- ming in patients with a left ventricular assist device. J Am Heart Assoc 7(5): e007748, 2018. 7. Grassi G, Vincenti A, Brambilla R, et al: Sustained sympathoinhibi- tory effects of cardiac resynchronization therapy in severe heart failure. Hypertension 44: 727–731, 2004. 8. Birks EJ: Molecular changes after left ventricular assist device sup- port for heart failure. Circ Res 113: 777–791, 2013. Role of Cardiac Resynchronization Therapy in Patients with Left Ventricular Assist Support Copyright © 2018 by the ASAIO DOI: 10.1097/MAT.0000000000000854 Disclosure: The authors have no conflict of interest to report.