Abstract 18099: Heart Rate and AV Delay Modify Left Ventricular Filling Vortex Properties

Abstract

Background: Intraventricular flow generates vortex structures during rapid filling which grow during diastole and vanish during ejection. Vorticity has been proposed to increase global chamber efficiency by optimizing filling flow transportation and coupling kinetic energy to ejection. It also improves blood mixing avoiding stasis. Vorticity has been related to chamber geometrical properties, but the effects of electrical events have never been characterized. We have recently developed and validated a new method that allows measuring vortex properties by processing conventional transthoracic color-Doppler sequences.

Methods: 27 patients carrying an implantable CRT device were studied after AV optimization (AVOPT - iterative method), longest AV (AVLONG), shortest AV (AVSHORT), CRT off (CRToff), and DDD AVOPT at 100 beats per minute (100BPM). Two-dimensional B-mode and conventional color-Doppler sequences of the full LV were obtained from an apical long-axis (Lax) view during each phase. Time-resolved maps of the 2D velocity fields were generated at high temporal resolution (> 100 Hz) using custom software by computing the optimal solution to the continuity equation that minimizes numerical errors. Circulation, energy, position, and radius of the main (antero-septal) and secondary (infero-lateral) vortices were estimated along the cardiac cycle.

Results: Compared to AVOPT, the main vortex component remained closer to the base during 100BPM (difference = -20% of Lax length, p< .05) and closer to the apex during AVMIN (diff= +11% of Lax, p< .05). Radius of the main and secondary vortices was larger during AVMAX (p< .05). Also circulation and energy of the secondary vortex were higher during AVMAX.

Conclusions: Heart rate and AV synchronicity influence vortex dynamics. These novel aspects of diastolic function can be studied by fluid dynamic quantitative analysis of color-Doppler echocardiograms.