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. The investigators think that this is because lymphatic vessels are able to grow and remove fluid to prevent congestion. The investigators do not know how lymphatic vessels grow. This study will investigate the blood levels of various proteins to try to figure out how the lymph vessels of people with long-standing heart failure might grow.