AN OPTICAL-DEVICE TO MEASURE THE DYNAMICS OF APEX ROTATION OF THE LEFT-VENTRICLE

Systolic counterclockwise rotation of the left ventricular apex with r espect to the base has been defined as left ventricular (LV) twist or torsion. If rotation of the base during systole is small, we hypothesi zed that the dynamics of twist can be well characterized through the m easurement of apical rotation alone. A device was designed to measure apical rotation in a simpler, more direct fashion, providing continuou s high-fidelity dynamic measurements. The device consists of a light s ource, 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, apic al rotation (measured in degrees) can be calculated from the position of the deflected light beam. The timing of apical rotation was compare d 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 maxim um apical rotation of -15-degrees just before the end of systole. Rapi d 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 pr essure-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 metho d to measure the dynamics of apical rotation continuously during inter ventions such as load changes.