[The effect of nitrates on the function of intact and ischemic myocardium (author's transl)].

The effects of Sodium Nitroprusside (NPN), of Isosorbidedinitrate (ISDN), and of a combined therapy with NPN and the intraaortic balloon pump (IABP) on left ventricular function and on local contraction patterns of normal and ischemic myocardial regions were studied. In acute experiments on 16 dogs the anterior descending branch of the left coronary artery was stenosed to produce a hypokinesia or dyskinesia of the anterior wall of the left ventricle. Regional myocardial function was assessed using the ultrasound transit time method. When the LV filling pressure was initially norman (LVedP 5.7 +/- 0.6mmHg) nitrate infusion (120 microgram/minn NPN: 800 microgram/min ISDN) resulted in an aggravation of the ischemic dysfunction. Conversely, with high initial filling pressure (LVedP 15.4 +/- 1.3MMHg) regional myocardial function in the ischemic area returned to normal under therapy. Additional application of the IABP further improved regional myocardial mechanics. It is concluded, that reduction of coronary perfusion pressure due to nitrate therapy becomes critical when coronary reserve is depleted. Compensation is however possible if ventricular wall stress can be reduced and thus the oxygen consumption and the extravascular component of coronary resistance are decreased. Only when the initial filling pressure is high these conditions are met.