EFFECTS OF AMINOPHYLLINE ON CARDIAC-FUNCTION AND REGIONAL MYOCARDIAL PERFUSION - IMPLICATIONS REGARDING ITS ANTIISCHEMIC ACTION

Aminophylline improves exercise capacity in patients with angina. Beca use this drug does not dilate epicardial coronary vessels, its benefic ial effect is from either a reduction of myocardial oxygen consumption or an improvement of myocardial blood flow distribution. This study w as performed to assess the effects of aminophylline on cardiac functio n and on regional myocardial perfusion to establish the mechanisms of its antiischemic action. In 10 patients during cardiac catheterization hemodynamic parameters and cardiac volumes were obtained during basel ine and after intravenous infusion of aminophylline. Aminiphylline dec reased left ventricular end-diastolic pressure (from 11 +/- 4 to 4 +/- 2 mm Hg, p < 0.001), mean right atrial pressure (from 5 +/- 2 to 2 +/ - 1 mm Hg, p < 0.01), and left ventricular end-diastolic volume (from 117 +/- 36 to 88 +/- 36 ml, p < 0.01); it increased peak dp/dt (from 1 931 +/- 329 to 2430 +/- 540 mm Hg/sec, p < 0.001) and heart rate (from 69 +/- 9 to 76 +/- 14 beats/min, p < 0.05) and did not modify systoli c aortic pressure (138 +/- 14 vs 137 +/- 16 mm Hg, p = not significant NS). Estimated oxygen consumption during aminophylline (6.7 +/- 1.3 ml/min/gm) was similar to that during baseline (6.7 +/- 1.4 ml/min/gm ). In another study in nine anesthetized dogs with a critical stenosis of the left anterior descending artery, myocardial perfusion was asse ssed by microspheres during control atrial pacing and during atrial pa cing after aminophylline; left atrial pressure was kept constant throu ghout the study. During the second atrial pacing, total blood flow in the myocardium supplied by the left anterior descending coronary arter y was similar to that observed during the control pacing (0.60 +/- 0.1 7 vs 0.60 +/- 0.16 ml/min/gm, p = Ns), but the endo/epi flow ratio was higher (0.59 +/- 0.29 vs 0.39 +/- 0.25, p < 0.05). Left atrial pressu re, mean aortic pressure, and heart rate were similar during both atri al pacings (14 +/- 8 vs 15 +/- 6 mm Hg, p = NS, 85 +/- 9 vs 88 +/- 13, p = NS, 178 +/- 16 vs 178 +/- 16 beats/min, p = NS, respectively). Th us aminophylline does not reduce myocardial oxygen consumption. It can improve myocardial ischemia through (1) left ventricular unloading wh ich is likely to result in a reduction of subendocardial extravascular compression; and (2) constriction of subepicardial vessels with redis tribution of blood flow toward the subendocardium.