Assessment of left ventricular contractility from late systolic stress-volume relations.

Abstract

Whether the end-systolic stress.sbd.end-systolic volume relation of the left ventricle (i.e., its tension-length relation) could be estimated from the analysis of a single ventriculogram was determined. For that purpose, the left ventricular (LV) wall stress and volume were computed frame by frame in 35 patients (15 controls, 11 patients with valvular disease, 6 with coronary artery disease and 3 with congestive cardiomyopathy). In all patients, a linear relation was observed between LV wall stress and volume during approximately the last 2/3 of ejection. Under basal conditions, the duration of this linear relation ranged from 100-260 ms (mean 155 ms; mean r = 0.97) with a positive slope (range 3.0-9.3 kdyn/cm5 per m2 in controls) and a negative volume intercept. During a positive inotropic intervention (atrial pacing at 120 beats/min) that increased peak positive dP/dt by 24% (P < 0.0002), the slope of this linear relation also increased by 24% (P < 0.0025), but ejection fraction was unchanged. Further studies in animals indicated that this slope was insignificantly affected by changes in LV afterload within a range of 70-200% of the control values. Within the range of LV afterload encountered in the studied patients, this slope remained directly proportional to the slope of the end-systolic stress.sbd.end-systolic volume relation. During LV ejection, there is a linear stress-volume relation, which can be determined easily from a standard ventriculogram. The slope of this relation, which depends directly on the tension-length relation of the ventricle, is more specific than ejection phase indexes in detecting alterations in LV inotropic state in the clinical setting.