Effects of intravenous nitroglycerin on hemodynamics and ischemic injury in patients with acute myocardial infarction.

In 24 patients with acute myocardial infarction intravenous nitroglycerin in 2 different dosages was administered and the effect on hemodynamics and extent of myocardial ischemia was investigated. According to the initial left ventricular filling pressure (LVFP) the patients were divided in Group I: LVFP below 20 mm Hg (13 patients) and in Group II: LVFP above 20 mm Hg (11 patients). Following an infusion of 3 mg of nitroglycerin in the first and 6 mg in the second hour, a significant decrease (P less than 0.0001) in the filling pressure (in Group I from 15 +/- 4 to 9 +/- 3 (+/-1 SD) and in Group II from 28 +/- 11 to 16 +/- 7 mm Hg) was observed. The mean arterial pressure decreased in both groups by an average of 9 mm Hg. The changes in the heart rate were minimal. The cardiac output decreased in Group I from 4.4 +/- 1.0 to 3.9 +/- 0.8 1/min (P less than 0.005) whereas in the group with left ventricular failure it increased significantly from a lowered initial value (3.4 +/- 1.0 to 4.0 +/- 1.1 1/min) (P less than 0.001). By using precordial mapping for estimation of ischemic injury in 12 patient sigma ST elevation decreased from 14.6 +/- 11.9 to 12.2 +/- 9.8 mV at a dose of 3 mg/h (P less than 0.03). The dose of 6 mg/h, however, was less effective on the extent of myocardial ischemia than 3 mg/h. Thus, the dosage of nitroglycerin may be critical in respect to infarct size, despite the beneficial hemodynamic effects of the drug.