Publisher Summary This chapter describes various aspects of the heart in stroke. There are various relationships between heart disease and stroke. Heart disease is implicated as a cause of brain infarction in 17% of cases. Embolic infarcts typically present with focal neurologic signs, maximum at onset and only 5% have a progressive or stuttering course. Rheumatic heart disease with atrial fibrillation is associated with a 17-fold increased risk of thromboembolism, with an annual stroke rate of 4%. Mitral stenosis places patients at higher risk. Patients undergoing coronary artery bypass graft surgery have approximately a 1–5% rate of stroke. The most common mechanism remains cardioembolic, although strokes due to carotid artery disease, air emboli, prolonged hypotension, and aortic plaques occur. Stroke can also adversely affect the heart. Electrocardiogram (EKG) changes are seen after subarachnoid hemorrhage, intracerebral hemorrhage, and less commonly after ischemic stroke. Common EKG changes include abnormal QT intervals, peaked T waves or T wave inversions, U waves, and arrhythmias that resolve in days to months. Morbidity and mortality based on these EKG changes are difficult to assess, but these patients may be at increased risk of sudden death immediately and in the months following stroke.