Intracoronary Nitrogylcerin and Regional Coronary Blood Flow Responses During Coronary Angioplasty in Patients

To examine the direct effects of nitroglycerin (NTG) on anterior regional coronary blòod flow, electrocardiographic and hemodynamic responses were measured immediately before, during, and after brief coronary occlusion in 17 patients undergoing left anterior descending coronary angioplasty (PTCA). Hemodynamic data and the time from the onset of coronary occlusion to 1.0 mm ST elevation or depression were compared for matched control and NTG occlusion periods. Ten seconds before the “NTG” occlusion, 200 μg of NTG was injected into the left coronary artery. Baseline and occlusion level great cardiac vein flow (thermodilution) was similar for both occlusion periods (93 ± 27 to 59 ± 23 mL/min for control; 95 ± 27 to 56 ± 22 mL/min for NTG occlusion). NTG reduced mean arterial pressure (91 ± 11 to 82 ± 15 mmHg, P < 0.05) during increased basal great vein flow (95 ± 27 to 127 ± 54 mL/min p < 0.01) immediately prior to occlusion. Great vein hyperemic flow after release of occlusion increased 21 ± 30% versus 36 ± 40% (P = ns) after control occlusion. There were no differences in heart rate or systolic‐heart rate pressure products, time to ischemic ST‐T wave changes or the maximal hyperemic responses from the control occlusion. These data suggest that during the initial minutes of coronary occlusion, the marked but transient coronary vasodilation induced by intracoronary NTG does not significantly modulate myocardial ischemia or regional coronary blood flow responses. The clinical benefits of NTG during PTCA most likely occur more through other mechanisms than direct myocardial flow augmentation. (J Interven Cardiol: 1988:1:1)