The most common etiology of atrial mass, a rare disorder, is thrombosis. However, tumors, vegetations and fibrosis may also be responsible. Today, 2-dimensional echocardiography is the primary imaging technique for screening patients with a suspected cardiac mass. We describe a 66-year-old woman with chronic atrial fibrillation who was being treated with an anticoagulant for a year. A left atrial thrombus, which produced signs simulating those of mitral stenosis became dislodged and obstructed the abdominal aorta and superior mesenteric artery. She did not survive operation.

Human myocardial tissue obtained at autopsy from ten patients was examined for content of the MB isoenzyme of creatine kinase (CK-MB). We wished to determine whether this isoenzyme is distributed homogeneously throughout the heart. In eight cases, there was no history or pathological evidence of heart disease. Two had a history of previous myocardial infarction; in these, tissue was obtained from sites distant from the scar. Difference was found between the CK-MB content of the right atrium and the left atrium, and between the right ventricle and left ventricle. In all cases, the CK-MB content of the right side of the heart significantly exceeded that of the left side of the heart. Statistically significant differences were also found between the CK-MB content of the anterior interventricular septum and that of the posterior septum. These topographical variations in CK-MB content may be related to differences in the density of contractile elements in various parts of the heart and, moreover, are not taken into account in the enzymatic estimation of infarct size.

After undergoing a stress test that showed abnormal findings, a patient with severe coronary arterial disease had an elevated concentration of the MB isoenzyme of creatine phosphokinase, in the presence of normal levels of creatine phosphokinase and myoglobin in the serum.

An elevated level of the MB fraction of creatine phosphokinase (CPK) with normal serum myoglobin and normal CPK values was found in a case of acute idiopathic pericarditis. The elevated serum CPK-MB isozyme is suggested to be an indicator of myocardial involvement accompanying acute pericarditis. The normal CPK and serum myoglobin values and the pattern of rapid decrease of CPK-MB level ruled out the possibility of acute myocardial infarction.