Levels of serum calcium, phosphorus, magnesium, SGOT, CPK, and LDH were measured in 61 patients admitted to a coronary care unit. In 34 the ECG and enzymes confirmed an acute myocardial infarction, whereas the remaining 27 did not have an acute myocardial infarction. The serum phosphorus declined significantly in those with the acute infarction compared to the control group. The fall was most marked in the third and fourth postinfarction day, and by the fifth day had returned to baseline values. The serum calcium and magnesium did not change significantly over the 5 days. Thus the fall in the serum phosphorus serves as a sensitive indicator of acute myocardial infarction.

A 44-year-old woman with marked eosinophilia, leukocytosis, congestive heart failure, and the murmur of mitral stenosis had a restrictive type of pulse contour at cardiac catheterization. A right atrial angiogram revealed a huge right atrium, a small right ventricle, and a dilated contractile outflow tract consistent with the diagnosis of Loeffler's endocarditis. A marked conduction delay at the atrial level was demonstrated by His bundle electrogram studies.

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The effects of phentolamine, 0-3 mg/min given intravenously for 15 minutes, on His bundle electrograms were studied in 11 patients with heart disease. Recordings were made at varied heart rates, using atrial pacing. Phentolamine significantly reduced the AH interval in every patient but it had no effect on the HV interval. Functional and effective refractory periods were measured with the use of the atrial extrastimulus technique. The effective refractory period of the atrium and atrioventricular node as well as the functional refractory period of the atrioventricular node all significantly decreased after phentolamine infusion. This improvement in conduction is probably mediated by a release of catecholamines.