Effects of Radial Left Ventricular Dyssynchrony on Cardiac Performance Using Quantitative Tissue Doppler Radial Strain Imaging

Our objective was to test the hypothesis that novel angle-corrected radial strain imaging can quantify left ventricular dyssynchrony associated with contractile impairment and improved with biventricular pacing. Eight open-chest dogs were studied by novel angle-corrected color-coded radial strain imaging and high-fidelity pressure-conductance catheters recording pressure-volume loops. Heart rate was controlled by right atrial pacing and all timing intervals were corrected by R-R interval (corrected interval = measured interval/(R-R interval)1/2). Left bundle branch block, simulated by right ventricular free wall pacing, resulted in marked radial dyssynchrony, which we defined as maximal time difference between peak segmental strain, from 39 ± 17 to 354 ± 49 milliseconds and stroke work decreased from 157 ± 40 to 60 ± 37 mJ, (P < .005 vs baseline). Depression of contractility by high-dose esmolol (end-systolic pressure-volume relationship from 5.7 ± 2.4 to 3.6 ± 1.0 mm Hg/mL) was associated with augmented dyssynchrony to 388 ± 53 milliseconds (P < .05 vs baseline right ventricular pacing). Biventricular pacing improved dyssynchrony to 55 ± 19 milliseconds and stroke work to 143 ± 33 mJ (P < .05 vs right ventricular pacing). Changes in radial dyssynchrony correlated significantly with 6-site average regional strain (r = −0.93 ± 0.05 individually, r = 0.80 overall) and stroke work (r = −0.88 ± 0.12 individually, r = −0.82 overall). Angle-corrected radial strain imaging has clinical potential to quantify mechanical dyssynchrony and effects of biventricular pacing.