[Changes in diameters of small pulmonary venous and arterial vessels after nitroglycerin (author's transl)]

Diameters of the small arterial and venous pulmonary vessels were studied in 17 patients, using selective pulmonary angiography. The majority had coronary heart disease. Pulmonary and systemic hemodynamics were also evaluated. In 11 patients, these procedures were repeated 3 minutes after the sublingual administration of 1.6 mg of nitroglycerin (Group I). The remaining 6 patients served as controls (Group II). In Group I, pulmonary circulatory pressures, left ventricular filling pressure, and pulmonary vascular resistance declined significantly compared with Group II. The diameters of the small pulmonary veins declined by more than 10 percent in Group I while remaining constant in Group II. Differences between the two groups in terms of the response of the small arterial vessels was less evident. Increases in vessel cross-sectional area were observed despite considerably reduced intravascular pressure. The increase in elasticity and capacitance of the pulmonary vessels following nitroglycerin is more pronounced on the venous than on the arterial side. These findings suggest that the pulmonary vascular bed contributes significantly to the therapeutically important pooling effect caused by nitroglycerin in the treatment of angina pectoris and pulmonary edema.