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

The aim of the study was to determine if the end-systolic stress-end-systolic volume relation of the left ventricle (i.e., its tension-length relation) could be estimated from the analysis of a single yen- triculogram. 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, six with coronary artery disease and three with congestive cardiomyopathy). In all patients, a linear relation was observed between LV wall stress and volume during approximately the last two-thirds of ejection. Under basal conditions, the duration of this linear rela- tion ranged from 100-260 msec (mean 155 msec; mean r = 0.97) with a positive slope (range 3.0-9.3 kdyn/cm'/m' in controls) and a negative volume intercept. During a positive inotropic intervention (atrial pac- ing 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-end-systolic volume relation. Thus, 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 therefore more specific than ejection phase indexes in detecting alterations in LV inotropic state in the clinical setting.