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Background: Optimal atrioventricular delay (AVD) achieves maximum cardiac output in patients undergoing cardiac resynchronization therapy (CRT). Nonoptimal AVD decreases left ventricular (LV) end-diastolic volume and causes loss of flow momentum prior to LV ejection., Objective: We investigated the potential role of energy dissipation (ED) in these changes in cardiac output through the study of intraventricular flow. We hypothesized that short and long AVD increases ED when compared with optimal AVD by altering the physiologic flow mechanics that preserve kinetic energy in the LV., Methods: Forty-four patients under CRT underwent echocardiographic LV flow analysis under optimal, short, and long AVD. LV ED and vortical flow in the inflow-outflow tract were studied during the end-diastolic and early systolic period, and paired comparisons were obtained between optimal and nonoptimal values., Results: ED in the left ventricle was minimal in optimal AVD and significantly increased with nonoptimal values (79.1 ± 27.5 J/m·sec in optimal AVD vs 96.5 ± 34.7 J/m·sec in short AVD; n = 18, P = .006; 123.3 ± 67.6 J/m·sec in optimal AVD vs 292.4 ± 202.5 J/m·sec in long AVD; P < .001). Increase in ED occurred due to inadequate flow redirection toward the outflow tract in short AVD and due to both turbulence and prolonged ineffective flow rotation in long AVD., Conclusions: Optimal AVD in resynchronization therapy favors physiological vortex flow patterns in the left ventricle during the end-diastolic and early systolic period. These patterns are altered when nonoptimal values are programmed, increasing ED., (Copyright © 2019 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.)

Background: Swirling flow, organized in vortices, contributes to adequate left ventricular function. In this study, we apply a novel echocardiographic flow-mapping technique, vector flow mapping (VFM), to evaluate the main characteristics of left ventricular vortices and its relation to filling parameters., Methods: Forty-eight subjects underwent conventional transthoracic echocardiographic examination with additional intracardiac flow assessment with VFM using a Aloka Alpha-10 system and experimental VFM analysis software. To analyze vortex behavior, its rotation direction, duration, location inside the left ventricle, size, and intensity were assessed in apical long-axis view. Its relation to conventional left ventricular filling parameters was then analyzed., Results: Two vortex components were consistently identified following each transmitral filling wave. The anterior component of these visualized vortices was analyzed, due to its higher significance in the cardiac cycle, following early filling (V1) and atrial contraction (V2). Differences were observed in several aspects of vortex behavior between V1 and V2, particularly in patients with normal left ventricular filling parameters. These differences may be related to varying roles of vortices in different periods of the cardiac cycle., Conclusions: Vector flow mapping allowed visualization and measurement of several parameters defining vortex behavior inside the cardiac cycle. The differences observed in these parameters between vortices in different phases of the cardiac cycle may be related to their role in optimizing cardiac function., (© 2014, Wiley Periodicals, Inc.)