Heart Rate and AV delay modify left ventricular filling vortex properties

Intraventricular flow generates a vortex ring during rapid filling that optimizes filling, couples inflow kinetic energy to ejection, improves blood mixing and avoids stasis. LV vorticity has been related to chamber geometrical properties, but the effects of electrical events have never been characterized, partly due to the difficulty of performing MRI in patients with implanted devices. We have recently developed a new method that allows measuring vortex properties by processing conventional transthoracic color-Doppler sequences. Using this modality, 27 patients carrying an implantable cardiac resynchronization device were studied after AV optimization at 100 beats per minute. Our results reveal that, compared to optimal AV, the main vortex component remained closer to the base during 100BPM (difference = -20{\%} of Lax length, p$<$ .05) and closer to the apex when AV is minimized (diff= +11{\%} of Lax, p$<$ .05). Radius, circulation and energy of the vortices were larger when AV is maximized (p$<$ .05). In conclusion, the duration of diastole, as modulated by heart rate and AV-delay, significantly modifies intraventricular vortex dynamics.