Persistent reduction in left ventricular asynergy in patients with acute myocardial infarction by intravenous infusion of nitroglycerin.

Abstract

I.v. nitroglycerin (NG) infusion in patients with acute myocardial infarction (AMI) has been shown to improve left ventricular function and myocardial perfusion and to decrease ischemic injury and creatine kinase (CK) indexes of infarct size. To determine whether early NG infusions in patients with AMI decreases the extent of left ventricular asynergy, 2-dimensional echocardiography was used to measure asynergic segments (akinesis and/or dyskinesia) at 4 serial short-axis levels from base to apex (mitral, M; chordal, C; midpapillary, MP; low papillary, LP) in 22 patients with a 1st anterior AMI. Patients were randomized between infusions of NG (n = 11) or 5% dextrose in water (controls, n = 11) within 5.6 h after the onset of pain. NG infusion rates were titrated to lower mean arterial pressure to an average level of 7% below control (but not below 80 mm Hg) and were maintained at this level for the duration of the infusions (39 h). After NG, left ventricular function improved as left ventricular filling pressure decreased (P < 0.005), and .SIGMA.ST on precordial ST segment mapping decreased (P < 0.001). These parameters did not change in control subjects. Computed CK infarct size was smaller in the NG group than in the control group (P < 0.05). Before the infusions, the mean extent of left ventricular asynergy (% left ventricular circumference) were similar in both groups: M, 18 vs. 21%; C, 22 vs. 23%; MP, 26 vs. 24%; LP, 32 vs. 29%. In addition, the computed total left ventricular asynergy (% surface area) was also similar for these 2 groups before therapy (25 vs. 25%). There was no change in left ventricular asynergy from pretreatment values by 1 h and 10 days among control subjects: M, 18 vs. 18 vs. 17%; C, 22 vs. 23 vs. 22%; MP, 26 vs. 26 vs. 22%; LP, 32 vs. 33 vs. 33%; total 25 vs. 25 vs. 24% (multiple measures analysis of variance). In contrast, there was a significant decrease (P < 0.001) in left ventricular asynergy from pretreatment values by 1 h and 10 days with NG: M, 21 vs. 10 vs. 8%; C, 23 vs. 12 vs. 10%; MP, 24 vs. 13 vs. 9%; LP, 29 vs. 14 vs. 10%; total, 25 vs. 12 vs. 9%. Thus the prompt decrease in left ventricular asynergy in the NG group persisted for at least 10 days or 7 to 9 days after NG infusions were stopped. These effects on hemodynamics, .SIGMA.ST, CK infarct size, and asynergy suggest that careful early and prolonged low-dose NG infusion might reduce the extent of infarction.