William S. Wilson

The effects of sublingual nitroglycerin on myocardial blood flow in patients with coronary artery disease or myocardial hypertrophy.

Abstract Using selective intracoronary injections of xenon-133 in saline, the effect of sublingual nitroglycerin on myocardial blood flow was studied in nine patients undergoing cardiac catheterization. One normal patient showed a 14 per cent increase in flow, 1 1 2 minutes after drug administration, with a subsequent decline to 8 per cent below control at 6 minutes. Four of five patients with coronary artery disease showed increased flows of 3 to 13 per cent at 1 1 2 to 2 minutes after taking the drug. In two of these subjects, flow decreased to 10 to 23 per cent below control at 5 1 2 minutes. In the remaining three subjects with cardiomegaly and left ventricular hypertrophy, nitroglycerin produced a decrease of 7 to 12 per cent in myocardial blood flow at 1 1 2 minutes and a further reduction to 15 to 17 per cent below control in two of the subjects at 5 minutes. These results are felt to substantiate the theory that in some patients with coronary artery disease, nitroglycerin exerts a biphasic action with an initial increase in myocardial blood flow followed by a decrease in flow as the systemic effects of the drug become manifest. This biphasic action was not seen in patients with cardiac enlargement and hypertrophy.

An Appraisal of the Double Indicator-Dilution Method for the Estimation of Mitral Regurgitation in Human Subjects

The amount of mitral regurgitation was estimated in 50 patients by an indicator-dilution technic and by the usual clinical, catheterization, operative, and autopsy criteria. There was a good correlation between the two estimates. Patients with significant mitral regurgitation (grade 2 or grade 3) had, with one exception, QR/QF ratios above 0.41. There were at least two instances where the calculated QR/QF was almost certainly falsely high. It seems likely that these discrepancies are related to the presence of an unusually large volume between the pulmonary artery and the femoral artery.

Effects of Total Cardiopulmonary Bypass on Pulmonary Vascular Resistance in the Calf

MANY congenital cardiac anomalies are associated with a high mortality rate among infants. Some of these defects would be amenable to surgical correction if these small patients, who are usually desperately ill, could withstand the necessary open-heart operations. Although it has seemed wise to avoid such operations in children less than two years old, we have always considered operating on the infant with a correctable cardiac lesion when it was believed that otherwise he would not survive. With equipment specially designed for the infants size, with precise control of blood volume, and with meticulous postoperative care, many of these infants have undergone open-heart operations with success.1-3 Nevertheless, the mortality rate for openheart operations in infancy continues to be higher than that in childhood, especially in the first six months of life. This is due partly to the nature of the congenital anomaly, but in addition, there are also more unexplained deaths among these patients after apparently successful operations. The studies reported here were undertaken to clarify the pathogenic mechanisms in such cases by observing the effects of total cardiopulmonary bypass in young calves. Our experimental subjects were calves two to three weeks old, and in these animals it was found that total cardiopulmonary bypass significantly increased the pulmonary vascular resistance. The mecha-