EFFECTS OF ACUTE MYOCARDIAL-INFARCTION ON THEOPHYLLINE ELIMINATION INRATS

We investigated the effect of acute myocardial infarction (MI) on the hepatic clearance of theophylline in rats using the coronary artery li gation model, After 48 hr of ligation, there were significant changes in left ventricular performance in the MI rats, compared with controls , as indicated by elevated left ventricular end-diastolic pressure, re duced mean arterial pressure, and reduced left ventricular systolic pr essure (20 +/- 2 vs, 12 +/- 3 mm Hg, p < 0.01; 90 +/- 6 vs. 101 +/- 6 mm Hg, p < 0.01; and 100 +/- 8 vs. 114 +/- 8 mm Hg, p < 0.01, respecti vely), Despite these changes, MI rats were able to maintain their card iac output at rest (77.9 +/- 6.8 vs. 77.2 +/- 9.2 ml/min), and there w as no change in mean central venous pressure (3 +/- 1 vs, 2 +/- 1 mm H g), Although hepatic perfusion and oxygenation were preserved (17.3 +/ - 2.2 vs, 18.7 +/- 3.3 ml/min and 127 +/- 27 vs, 125 +/- 19 mu mol/min respectively), clearance of theophylline was reduced by 23% in the MI rats, compared with controls (0.86 +/- 0.20 vs. 1.12 +/- 0.17 ml/min, p = 0.01). There was no significant correlation between theophylline clearance and the infarct size (r = -0.038, p > 0.05), These findings demonstrate that the elimination of theophylline is impaired after acu te MI, independent of any changes in hepatic perfusion or oxygenation.