The effect of inotropics on
myocardial ischemia is difficult to predict, since inotropics may influence the determinants of myocardial O2-demand and O2-supply differently. Several
phosphodiesterase-inhibitors have been reported to possess antiischemic properties related in vivo to their hemodynamic and O2-sparing effects. The effects of
amrinone (CAS 60719-84-8) (10(-6) mol/l or 5 x 10(-5) mol/l) or
milrinone (CAS 78415-72-2) 10(-5) mol/l) on
myocardial ischemia extent and
infarct size were compared in isolated electrically paced rabbit hearts (Langendorff, constant pressure: 70 cm H2O, Tyrode
solution, Ca2+ 1.8 mmol/l).
Myocardial ischemia was induced by left coronary artery branch occlusion and quantitated from epicardial
NADH-fluorescence photography.
Infarct size was determined by
Evan's blue dye and
nitroblue-tetrazolium staining and planimetry. At low concentration (10(-6) mol/l),
amrinone had no significant influence on left ventricular pressure or coronary flow (p < 0.05) and epicardial
NADH-fluorescence area or
infarct size were not significantly affected compared to controls (p > 0.05).
Amrinone (5 x 10(-5) mol/l) or
milrinone (10(-5) mol/l) significantly increased left ventricular pressure (+10%, p < 0.05) and coronary flow (+30, 40%, p < 0.05) to a similar extent. Concomitantly, both agents similarly reduced epicardial
NADH-fluorescence area (-25%, p < 0.05) and
infarct size relative to the area at risk or ventricle size compared to controls (p < 0.05).
CONCLUSION: