A NEW METHOD TO MEASURE REGIONAL MYOCARDIAL TIME-VARYING ELASTANCE USING MINUTE VIBRATION

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 v entricular surface at various frequencies (50-100 Hz). Using the measu red displacement and force between the vibrator head and myocardium, w e 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 x 10(6) dyn/cm) to systole (0.833 +/- 0.391 x 10(6) d yn/cm). The end-systolic elastance (e(es)) linearly correlated with en d-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 corona ry occlusion. Young's modulus, estimated by normalizing e(es) by the w all 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 x 10(6) dyn/cm(2) at the ischemic reg ion after coronary occlusion (P < 0.005). We conclude that this techni que is useful for the quantitative assessment of regional myocardial e lastance.