Myocardial Blood Flow in Man Measured by a Coincidence Counting System and a Single Bolus of 84 Ribidium Chloride

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Abstract
Using a coincidence counting system and a single bolus injection of 84RbCl, the effect of sublingual nitroglycerin (0.6 mg) on myocardial blood flow (MBF) in normal human subjects was studied. Concomitant pressure time per minute work of the heart was calculated as the product of heart rate, systolic mean pressure, and systolic ejection period. Seventeen subjects were studied. In seven, repeat measurements were made 3 minutes after administration of nitroglycerin and in 10 subjects 10 minutes after the drug was given. There was no predictable direction of change in myocardial blood flow, seven subjects showing an increase and 10 subjects a decrease. There was a highly significant correlation (P<0.001), however, between the changed in myocardial blood flow and concomitant pressure time. It is concluded that sublingual nitroglycerin does not a priori increase myocardial blood flow in normal man at 3 or 10 minutes; rather, the changes may be related to changes in myocardial oxygen requirements. It would appear, thus, that nitroglycerin does not alter the autoregulatory vessels of the heart.