A new method to measure regional myocardial time-varying elastance using minute vibration

Abstract

We developed a new technique to evaluate regional myocardial elastance using minute vibration. In 13 isolated cross-circulated canine hearts, we applied small sinusoidal vibrations of displacement to the left ventricular surface at various frequencies (50–100 Hz). Using the measured displacement and force between the vibrator head and myocardium, we derived myocardial elastance on the basis of the equation of motion for a given moment of the cardiac cycle. Simultaneous solution of the equations of motion at different frequencies yielded a unique value of elastance. Time-varying myocardial elastance increased from diastole (0.028 ± 0.211 × 106 dyn/cm) to systole (0.833 ± 0.391 × 106 dyn/cm). The end-systolic elastance ( e es) linearly correlated with end-systolic left ventricular elastance ( r = 0.717, P < 0.001) and also with the end-systolic Young’s modulus ( r = 0.874, P < 0.0001). We also measured e es at both ischemic and nonischemic regions during coronary occlusion. Young’s modulus, estimated by normalizing e es by the wall thickness and by the estimated mass, did not change significantly at the nonischemic regions, whereas it decreased significantly from 2.303 ± 0.556 to 1.173 ± 0.370 × 106dyn/cm2 at the ischemic region after coronary occlusion ( P < 0.005). We conclude that this technique is useful for the quantitative assessment of regional myocardial elastance.