Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we will assume that you are happy to receive all cookies and you will not see this message again. Click 'Find out more' for information on how to change your cookie settings.

BACKGROUND: Molecular remodeling in heart failure includes slowing of repolarization, leading to proarrhythmia. OBJECTIVE: To evaluate the effects of Na(+)/Ca(2+) exchanger (NCX) inhibition on repolarization as a novel antiarrhythmic concept in chronic heart failure (CHF). METHODS AND RESULTS: CHF was induced by rapid ventricular pacing in rabbits. Left ventricular function was assessed by echocardiography. Monophasic action potentials (MAPs) showed a prolongation of repolarization in CHF after atrioventricular block and stimulation at different cycle lengths. Sotalol (100 μM, n = 13) or veratridine (0.5 μM; n = 15) resulted in a further significant increase in the MAP duration. CHF was associated with an increased dispersion of repolarization, as compared with sotalol-treated (+22 ± 7 ms; P < .05) and veratridine-treated (+20 ± 6 ms; P < .05) sham hearts. In the presence of a low potassium concentration, sotalol and veratridine reproducibly induced early afterdepolarizations (EADs) and polymorphic ventricular tachyarrhythmias (VTs). SEA0400 (1 μM), a pharmacological inhibitor of NCX, significantly shortened the MAP duration (P < .01) and reduced dispersion (P < .05). It suppressed EAD in 6 of 13 sotalol-treated failing hearts and in 9 of 10 veratridine-treated failing hearts, leading to a reduction in VT (60% in sotalol-treated failing hearts and 83% in veratridine-treated failing hearts). Simulations using a mathematical model showed a reduction in the action potential duration and the number of EADs by the NCX block in all subgroups. CONCLUSIONS: In an experimental model of CHF, the acute inhibition of NCX (1) reduces the MAP duration, (2) decreases dispersion of repolarization, and (3) suppresses EAD and VT. Our observations indicate for the first time that pharmacological NCX inhibition increases repolarization reserve and protects against VTs in heart failure.

Original publication

DOI

10.1016/j.hrthm.2011.11.004

Type

Journal article

Journal

Heart Rhythm

Publication Date

04/2012

Volume

9

Pages

570 - 578

Keywords

Action Potentials, Amiodarone, Animals, Anti-Arrhythmia Agents, Disease Models, Animal, Heart, Heart Failure, Heart Ventricles, Humans, Long QT Syndrome, Rabbits, Sodium-Calcium Exchanger, Sotalol, Tachycardia, Ventricular, Torsades de Pointes, Veratridine