Evolution of Abnormalities in Left Ventricular Function after Acute Myocardial Infarction

Abstract

Twelve patients with acute myocardial infarction (AMI) were studied by left ventricular (LV) catheterization, echocardiography, and volume manipulation (tourniquets, phlebotomy, and dextran infusion) within 24 hours of infarction (study 1) and 3 weeks later (study 2). Three patients also were studied 6-10 months later (study 3). Cardiac index rose (from 2.50 to 3.15 liters/min/m ² ) and right atrial pressure fell (from 9.4 to 5.3 mm Hg) from study 1 to study 2. LV end-diastolic pressure (LVEDP) remained elevated (21.8 mm Hg at study 1 and 20.9 mm Hg at study 2) and was actually higher at study 2 in six patients who were otherwise improved. At study 1, end-diastolic ventricular diameter was within normal limits in five patients with clinical LV failure, four of whom had grossly elevated LVEDP. At study 2, ventricular diameter remained normal in three patients with elevated LVEDP but no LV failure. At study 3, LVEDP was still elevated in two patients and chamber diameter normal in two and slightly increased in one. Ventricular function curves (LVEDP vs stroke index) constructed from results during volume manipulation showed no consistent improvement during convalescence. These data indicate that clinical improvement after AMI is not usually associated with a fall in LVEDP or a normalization of the impaired LV function curve. Normal ventricular diameter indicates normal ventricular volume which, in the presence of an elevated LVEDP, suggests a persistent decrease in LV compliance.