Impact of Cardiac Resynchronization Therapy on Right Ventricular Function in Left Ventricular Assist Device Patients

Left Ventricular Assist Devices (LVAD) are mechanical heart pumps that are increasingly being implanted in patients with severe heart failure which have failed medical therapy. In patients with LVADs, right ventricular failure, which is not supported by the LVAD pump, is a major problem that affects quality-of-life and survival. Cardiac Resynchronization Therapy (CRT) aims to restore the synchronized contraction of the heart and has proven to be beneficial for improving ejection fraction of both right and left ventricle as well as quality of life in selected heart failure patients. The role of CRT in patients with LVADs is unknown. We hypothesize that CRT can exert a beneficial impact on right ventricular function in LVAD patients and improve their quality-of-life. The specific questions that this study aims to answer are: 1. What are the effects of CRT on the function of the non-supported right ventricle in patients with an implanted LVAD? 2. Can the effects of CRT on cardiac function positively impact quality-of-life and exercise capacity in LVAD recipients? In this study patients with a previously implanted CRT device, who later receives an LVAD, will be randomly assigned to have the CRT turned off (CRT-off) or on (CRT-on). The patients will be followed for an 8-week period, and then switched over to the opposite CRT status. The total participation in this study will last for 16 ± 1 weeks, and will involve 3 clinic visits of approximately 3 hour duration (initial visit, 8 week visit, and 16 week final visit), plus 2 quick checks of the pacemaker/defibrillator in-between the visits. Heart function will be assessed with comprehensive echocardiographic studies during the CRT "on" and CRT "off" periods. Quality-of-life and exercise capacity will be assessed with a standardized questionnaire and a 6-Minute Walk Test.