- Major risk cardioembolic source of embolism such as: a) intracardiac thrombus as evidenced by transthoracic or transesophageal echocardiography, b) paroxysmal, persistent or permanent AF, c) atrial flutter, d) prosthetic cardiac valve (mitral or aortic, bioprosthetic or mechanical), e) atrial myxoma, f) other cardiac tumors, g) moderate or severe mitral stenosis, h) recent (< 4weeks) myocardial infarction, i) valvular vegetations, or j) infective endocarditis.