Regional Left Ventricular Performance in the Year following Myocardial Infarction

Abstract

The relationship of abnormal regional myocardial performance to left ventricular (LV) function 2-12 months following transmural myocardial infarction was investigated in 25 patients by quantitative biplane angiocardiography. Abnormally contracting segments (ACS) (akinetic or dyskinetic) of the LV were identified in 24 patients. Their sites correlated with the electrocardiographic locations of infarction. ACS were expressed as a percentage (ACS%) of the end-diastolic ventricular circumference, and the percentages obtained correlated with ejection fraction (EF) (r = —0.838, P = 0.0001) using a quadratic regression equation. The group of patients (N = 8) with heart failure (paroxysmal nocturnal dyspnea and/or ventricular gallop sound) demonstrated a significantly lower mean value for EF (P = 0.0003) and a significantly larger mean value for ACS% (P = 0.0041) than the group of patients (N = 16) without heart failure. EF sharply separated the two groups. ACS% was a poor separator because in the majority of patients in both groups it was between 14 and 38%. Since EF sharply separated the heart failure and non-heart failure groups but ACS% did not, a theoretic model was developed to assess the contribution of the remaining myocardium to LV function. The curve described by the model did not differ significantly from the curve derived from the quadratic regression equation. Data from heart failure and non-heart failure patients were generally separated by a point (EF = 0.30, ACS = 23%) on the theoretic curve. Abnormal function of the nonakinetic myocardium was considered to be present when observed EF was lower than predicted EF for the observed ACS%. Thus, within the year following transmural myocardial infarction, the relative size of an abnormally contracting region of the ventricle was quantitatively related to impairment of LV function. The spherical model not only provided a framework for relating the clinical status of a patient to both ventricular function and size of the ACS, but also offered a means of estimating the function of the myocardium that appeared angiographically to be nonakinetic.