Objectives: The purpose of this study was to enhance understanding of the working mechanism of cardiac resynchronization therapy by comparing animal experimental, clinical, and computational data on the hemodynamic and electromechanical consequences of left ventricular pacing (LVP) and biventricular pacing (BiVP).
Background: It is unclear why LVP and BiVP have comparative positive effects on hemodynamic function of patients with dyssynchronous heart failure.
Methods: Hemodynamic response to LVP and BiVP (% change in maximal rate of left ventricular pressure rise [LVdP/dtmax]) was measured in 6 dogs and 24 patients with heart failure and left bundle branch block followed by computer simulations of local myofiber mechanics during LVP and BiVP in the failing heart with left bundle branch block. Pacing-induced changes of electrical activation were measured in dogs using contact mapping and in patients using a noninvasive multielectrode electrocardiographic mapping technique.
Results: LVP and BiVP similarly increased LVdP/dtmax in dogs and in patients, but only BiVP significantly decreased electrical dyssynchrony. In the simulations, LVP and BiVP increased total ventricular myofiber work to the same extent. While the LVP-induced increase was entirely due to enhanced right ventricular (RV) myofiber work, the BiVP-induced increase was due to enhanced myofiber work of both the left ventricle (LV) and RV. Overall, LVdP/dtmax correlated better with total ventricular myofiber work than with LV or RV myofiber work alone.
Conclusions: Animal experimental, clinical, and computational data support the similarity of hemodynamic response to LVP and BiVP, despite differences in electrical dyssynchrony. The simulations provide the novel insight that, through ventricular interaction, the RV myocardium importantly contributes to the improvement in LV pump function induced by cardiac resynchronization therapy.
Keywords: % change in maximal rate of left ventricular pressure rise; % change in maximal rate of right ventricular pressure rise; ANOVA; AT(TOT); AV; BiVP; CRT; ECM; HF; LBBB; LV; LVP; LVdP/dt(max); RV; RVdP/dt(max); analysis of variance; atrioventricular; biventricular pacing; cardiac resynchronization therapy; dyssynchrony; electrocardiographic mapping; electrophysiology mapping; heart failure; left bundle branch block; left ventricle/ventricular; left ventricular pacing; myocardial work; right ventricle/ventricular; total ventricular activation time; ventricular interaction.
Copyright © 2013 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.