Contractile State of the Left Ventricle in Man

Abstract

The contractile state of the left ventricle in man was analyzed by correlating left ventricular (LV) dimensional changes during contraction determined from cineangiograms, with simultaneous measurements of LV pressure. The mechanical characteristics of ventricular contraction were expressed quantitatively by deriving the extent and velocity of circumferential fiber shortening at the midwall and the time course of LV wall tension (stress); the instantaneous relations between tension, velocity, and length were then examined. In 6 patients without LV disease, wall tension became maximal soon after the onset of ejection, then declined rapidly; in 9 patients with LV disease, tension fell only slightly with continued ejection. The extent of shortening of the minor LV circumference was consistently less in patients with LV disease than in those without such disease. Velocity of circumferential fiber shortening throughout contraction ranged from 0.22 to 1.11 circumferences/sec in patients with LV disease and from 1.66 to 2.71 circumferences/sec in patients without LV disease, at comparable levels of wall tension (137 to 467 g/cm², and 175 to 409 g/cm², respectively). The initial rate of change of velocity of the circumferential fibers at the onset of ejection also was less than in the group without LV disease. The velocity of shortening of the contractile elements at maximum wall tension was 0.11 to 0.87 circumferences/sec in patients with LV disease and 1.46 to 2.04 circumferences/sec in patients without LV disease.