Background: To reverse preexisting coronary graft spasm, we investigated the vasodilative effect of the average therapeutic plasma concentration of nitroglycerin (NTG) alone and various calcium antagonists in combination with NTG in human arterial and venous conduits.
Methods: Vasodilative effects of 2 x 10(-8) mol/L NTG alone and 10(-8) mol/L NTG in combination with 2.2 x 10(-7) mol/L diltiazem, 2.8 x 10(-7) mol/L nifedipine, 10(-7) mol/L verapamil, or 5.6 x 10(-8) mol/L nicardipine were assessed in human radial artery, internal thoracic artery, and saphenous vein segments precontracted with a mixture of ten times the maximum plasma concentrations of endothelin-1 (8.6 x 10(-13) mol/L), angiotensin II (36 x 10(-11) mol/L), 5-hydroxytryptamine (3.4 x 10(-7) mol/L), and norepinephrine (1.7 x 10(-8) mol/L). The studies were done in organ baths.
Results: The therapeutic concentration of NTG alone or nifedipine, verapamil, diltiazem, or nicardipine in combination with NTG caused equal relaxation in a particular group of vascular segments (average vasodilation: radial artery, 83% to 95% [p = 0.7608 by analysis of variancel; saphenous vein, 47% to 70% [p = 0.3142]; internal thoracic artery, 54% to 79% [p = 0.27831). These combinations were not equally effective when compared between different groups of vascular segments (vasodilation; radial artery > internal thoracic artery > saphenous vein [p < 0.0001 by analysis of variance]). Although not significant, in comparison with NTG alone, NTG in combination with a calcium antagonist caused less vasodilation in any group of vascular segments.
Conclusions: Nitroglycerin alone or in combination with nifedipine, verapamil, diltiazem, or nicardipine effectively reverses preexisting vasospasm in coronary artery conduits.