Augmentation of mortality risk discriminating power of left ventricular ejection fraction by measures of nonuniformity in systolic emptying on radionuclide ventriculography

Abstract

Employing equilibrium-gated radionuclide ventriculography in the left anterior oblique view, six geometric models and five mathematic coefficients of nonuniformity in regional left ventricular emptying were tested for their relative mortality risk-stratifying power and capacity to augment the risk-discriminating potency of the continuous and dichotomized global ejection fraction. Radionuclide ventriculography was performed an average of 7.6 days after acute myocardial infarction. All geometric models significantly separated 20 normal subjects from 137 patients with recent infarction (p < 0.001).Cumulative mortality data demonstrated that significant independent univariate dichotomizing potency and augmentation of the mortality risk-discriminating power of the global ejection fraction were provided by models of regional emptying that 1) conformed to coronary artery perfusion areas, 2) encompassed total ventricular counts, 3) expressed variability in regional relative to global ejection fraction, and 4) simulated a pattern of emptying directed toward the center of geometry of the left ventricle.The combination of a four quadrant geometric model with axes drawn 45° above the horizontal and a coefficient of variation calculated as √σ(GEF − REF)2/4 × 100/ GEF (where GEF = global ejection fraction and REF = regional ejection fraction) proved to be optimal. This coefficient averaged 12.2% in normal subjects and 322% in patients with recent acute myocardial infarction (p < 0.001). It dichotomized the initial patient cohort into those with a synergic left ventricle (n = 64) with a 4 year cumulative survival rate of 9.1% and those with an asynergic left ventricle(n = 73) with a cumulative survival rate of 29.3% (p ≤ 0.005). The coefficient augmented the risk-discriminating power of the continuous global ejection fraction (p = 0.020) and the ejection fraction dichotomized at 0.40 (p = 0.009).These data demonstrate that measures of nonuniformity in ventricular emptying add significantly to the mortality risk discrimination provided by the global ejection fraction after acute myocardial infarction.