For some patients with heart failure, we know that using a special pacemaker configuration called cardiac resynchronization therapy (CRT) can help them feel better and live longer. In fact, in these patients, we can see improvements in cardiac function with CRT as early as a few beats after we turn it on. However, some patients continue to be sick after CRT and ultimately require more help. Some of these patients will get a surgically implanted pump (called a left ventricular assist device, or LVAD) that does the work of their heart. We do not know if CRT continues to help (or may hurt) these patients. In this study, we will assess the effects of CRT in LVAD patients in the short term.

Heart failure often causes fluid to accumulate in the body, leading to congestion and swelling. However, some people who have had heart failure for a long time seem to have very little congestion or swelling, even when the heart failure is poorly treated. We think that this is because lymphatic vessels are able to grow and remove fluid to prevent congestion. We do not know how lymphatic vessels grow. This study will investigate the blood levels of various proteins to see if we can figure out how the lymph vessels of people with long-standing heart failure might grow.