When a heart is damaged or weakened, it moves less blood with each heart beat, and fluid backs up in the lungs. Less blood moving through your body also results in less oxygen being delivered to organs like your kidneys, which help your body get rid of excess water. If the kidneys don't receive the oxygen they need to function properly, excess water may collect in different parts of your body, causing them to become congested with fluid. Many conditions can weaken the heart and cause congestive heart failure. Over time, arteries that supply blood to your heart muscle can become narrowed from fatty deposits.
Blood moves more slowly through narrowed arteries.
As a result, some areas of your heart muscle may be chronically deprived of oxygen-rich blood. These areas of your heart may become weak from the lack of oxygen and pump less vigorously. Heart attack . A heart attack occurs when a blood clot forms in a narrowed heart artery, blocking blood flow to a portion of your heart muscle and damaging it. The damaged portion of the heart can no longer pump as well as it should.