Effects of load manipulations, heart rate, and contractility on left ventricular apical rotation: An experimental study in anesthetized dogs

Background: Left ventricular twist or torsion has been de fined as the counterclockwise rotation of the ventricular apex with respect to the base during systole. We have recently shown that since base relation is minimal, measurement of apex rotation reflects the dynamics of left ventricular (LV) twist. Since the mechanisms by which load and contractility affect twist are controversial, we aimed to determine the relation between apex rotation and volume, contractility, and heart rate under conditions in which dimensions and pressures were accurately measured. Methods and Results: Using our optical device coupled to the LV apex, apex rotation was recorded simultaneously with LV pressure. ECG, LV segment length, and minor-axis diameters (sonomicrometry) in 12 open-chest dogs. Using vena caval occlusion and volume leading, a linear end-diastolic (ED) relation between apex rotation and LV area index was obtained (slope, 0.61±0.06°/percent change; intercept, -60.1±6.2°; n=10) that differed from the end-systolic (ES) relation (slope, 1.36±0.27°/percent change; intercept, 132.5±24.9°; P