Mechanisms of Preejection and Postejection Velocity Spikes in Left Ventricular Myocardium

Abstract

Background— Normal left ventricular myocardium demonstrates distinct spikes in the velocity trace before and after left ventricular ejection. We tested the hypothesis that the preejection and postejection velocity spikes reflect early systolic shortening and late systolic lengthening that are interrupted by mitral and aortic valve closure, respectively. Methods and Results— In 11 anesthetized dogs, timing of valve closure was determined by pressure variables; left ventricular dimensions were determined by sonomicrometry. Myocardial shortening started 20±10 ms (mean±SD; P P P =0.036), indicating that preejection shortening was larger with a leaking valve. Similarly, late systolic lengthening was reduced in patients (n=15) with severe aortic regurgitation after prosthetic valve replacement; minimum postejection velocity spike was increased from −32±11 to −17±11 mm/s; P =0.0003). Asynchronous onset of contraction/relaxation and atrioventricular interaction were investigated as alternative mechanisms of the velocity spikes in dogs and patient groups but were found implausible. Conclusions— This study supports the hypothesis that normal left ventricular preejection and postejection velocity spikes are attributed to valve closures that interrupt early systolic shortening and late systolic lengthening, respectively.