The 12-lead electrocardiogram in exercise testing. A misleading baseline?

Mason and Likar reported a modified ECG lead system that largely eliminates intraexercise artifact without reportedly altering the configuration of the recorded leads. This system allows continuous monitoring of all 12 leads during and after exercise and has become the standard by which other systems are compared. We have found, however, that important changes may be seen between the baseline exercise ECG using the Mason-Likar modification and a simultaneous standard ECG. While these differences do not apparently affect the interpretation of the test, they may produce or obscure evidence of antecedent infarction on the baseline exercise ECG and thus preclude it from being considered interchangeable with a standard ECG.

Bilateral atrial myxomas. Preoperative diagnosis and successful removal.

A case of bilateral atrial myxomas is presented. The diagnosis was made preoperatively with the aid of echocardiography and cineangiography. The use of the echocardiogram in the diagnosis of this lesion is emphasized.

Congenital aneurysm of the sinus of Valsalva protruding into the left ventricle. Review of diagnosis and treatment of the unruptured aneurysm.

During a routine physical examination, a 34-year-old man, in apparent good health, had an electrocardiogram which revealed left axis deviation. Cardiac evaluation disclosed mild aortic regurgitation and left anterior fascicular block. Nine months later, the patient was admitted to the critical care unit after he had experienced cardiac arrest while jogging. Angiograms demonstrated a large unruptured aneurysm in the right coronary sinus of Valsalva protuding into the left ventricle. Echocardiographic manifestations also suggested also suggested a sinus of Valsalva aneurysm. The defect was repaired through an aortic approach. The aneurysmal sac was emptied and the neck sutured securely. Twenty-two months postoperatively, the patient continues to be asymptomatic. We anticipate that this will decrease the threat of recurrent arrhythmias..

Vena caval interruption in pulmonary hypertensive canines.

Massive pulmonary embolism regularly causes a reduction in systemic arterial pressure. This is accompanied by an increase in pulmonary arterial pressure. If right heart strain is sufficient, peripheral venous pressures also rise. Initial cardiac output and heart rate responses are variable, but with the progression of time, cardiac output almost uniformly falls. When either vena caval clipping or vena caval ligation are performed in the face ot these altered hemodynamics, there is a further reduction of systemic arterial pressure and cardiac output. After a period of 90 to 120 minutes, the effects of the two procedures appear to be equivalent. This is thought to be on the basis of opening of venous collateral pathways in the case of vena caval ligation. Therefore, when sufficient venous collaterals are present, the major determinant of the ultimate outcome is the impact of the embolus itself rather than the type of procedure used to interrupt the inferior vena cava.

Increase in P50 with the use of bicarbonate hemodialysis.

We studied the effect of bicarbonate and acetate on oxygenation during dialysis in ten male chronic dialysis patients. The dialysis delivery system and dialysate constituents were identical except for the use of either bicarbonate or acetate. We found no hemodynamic differences between the two kinds of dialysis. Blood PO2 fell by a similar amount, but blood PCO2 was higher during bicarbonate dialysis. The blood pH became alkalotic by the second hour of bicarbonate dialysis and remained so throughout the dialysis, whereas blood pH became alkalotic only at the end of acetate dialysis. The P50 increased significantly only during bicarbonate dialysis, but 2.3 DPG concentration did not change. Red cell volume, assessed by the mean corpuscular hemoglobin concentration, was unchanged. Without changes in the red cell volume we cannot explain the observed changes in P50 in the absence of concomitant changes in 2.3 DPG concentration.