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Systolic counterclockwise rotation of the left ventricular apex with respect to the base has been defined as left ventricular (LV) twist or torsion. If rotation of the base during systole is small, we hypothesized that the dynamics of twist can be well characterized through the measurement of apical rotation alone. A device was designed to measure apical rotation in a simpler, more direct fashion, providing continuous high-fidelity dynamic measurements. The device consists of a light source, a position-sensitive diode, and a small rotating mirror that is coupled to the apex of the heart by a wire. As the wire rotates, apical rotation (measured in degrees) can be calculated from the position of the deflected light beam. The timing of apical rotation was compared with simultaneous recordings of electrocardiogram, LV pressure, and LV diameter measurements. An initial clockwise rotation (untwist) of 4 +/- 2 degrees (SD) occurred during isovolumic contraction followed by counterclockwise rotation (twisting) through ejection, reaching maximum apical rotation of -15 degrees just before the end of systole. Rapid untwisting during isovolumic relaxation was shown with near-complete dissipation of twist by the first one-third of the diastolic filling period. Caval occlusion caused a downward and leftward shift of the pressure-apical rotation loops, and more twist/untwist was seen to occur during the respective isovolumic contraction and relaxation periods. We conclude that this device provides precise timing and definition of rapid changes during isovolumic contraction and relaxation, confirms results obtained by more laborious methods, and provides an easy method to measure the dynamics of apical rotation continuously during interventions such as load changes.
Kroeker et al. (Fri,) studied this question.