What causes a blood clot in heart. How long will it take for heparin to break up the blood clot?

Variable. Acute heart attack and surface clot quite quickly! atrial fibrillation/ mitral vale may develop more slowly. Heart failure and enlarged chambers. Heparin reduces progression, but natural clot lysis occurs over time naturally or with lyric agents.
Variety of causes. A variety of disorders can result in a blood clot within the heart. These range from genetic disorders to trauma to cancer syndromes. Most clots dissolve after a few months with heparin, but others need to be surgically removed. Blood thinners are usually continued at least 6 months, but sometimes indefinitely for the rest of the patient's life, depending on the cause of the clot.