[Effects of injectable nitroglycerin on atheromatous coronary stenoses]

The beneficial effects of glyceryl trinitrate (GTN) are the result of several mechanisms which reduce venous return, cardiac work and intraparietal tension, and redistribute blood flow to the subendocardial layer and ischaemic zones. A direct action on atheromatous coronary stenosis is disputed. The coronary angiogram of 45 patients with organic stenosis and no clinical or electrocardiographic signs of coronary spasm were studied under basal conditions and after intravenous injection of 1.5 mg of GTN. Eighty stenotic segments and the corresponding 80 prestenotic segments were traced for comparison after enlargement on a Vanguard retroprojector and calibrated with reference to the coronary angiographic catheter. Aortic pressure fell 2 minutes after the injection in all patients to return to initial values at the end of the investigation. The diameter of the stenosed segment increased in 17 cases, remained unchanged in 54 cases and decreased in 9 cases. When expressed as a percentage of stenosis, the narrowing increased in 25 cases, decreased in 16 cases and remained the same in 39 cases. In the cases aggravated by GTN the diameter of the stenosis decreased or remained the same, whilst the diameter of the prestenotic decreased; in the cases improved by GTN, the diameters of both stenotic and prestenotic segments increased and prestenotic segments showed only slight variations. There was no difference in the diameter of the prestenotic segments between the 3 groups, but the diameter of the stenotic segments was larger in the group aggravated by GTN in comparison with the other two groups. Different haemodynamic factors and neurotumoral and local metabolic autoregulatory mechanisms may be activated by GTN.(ABSTRACT TRUNCATED AT 250 WORDS)