The immediate effect of nitroglycerin on total body blood volume distribution in patients with congestive heart failure: a non-invasive study.

The effect of sublingually administered nitroglycerin (0.5 mg) on distribution of blood volume in 16 patients with congestive heart failure (NYHA class II and III), randomly assigned to placebo (N = 8) or nitroglycerin (N = 8) was studied 20 minutes after in vivo labelling of red blood cells with 99m-Tc pertechnetate. Count rates over thorax, abdomen and legs were collected with a large field gamma camera and expressed as percentage changes of baseline value. Changes in count rates, averaged for 5, 10 and 15 minutes after drug administration showed a significant decrease in the nitroglycerin group as compared to the placebo group over the thorax (mean 5%, P less than 0.01) and over the liver (mean 5%, P less than 0.05) and a significant increase over the abdomen (mean 4%, P less than 0.01) and the legs (mean 9%, P less than 0.01). After nitroglycerin, the changes in pulmonary activity were variable and did not differ from the placebo group. These results indicate that nitroglycerin causes a redistribution of blood volume in patients with congestive heart failure. An increase in the vascular capacitance in the abdomen and legs may be responsible for a decrease of blood volume of the thorax and the liver in these patients.