Nonalternans repolarization variability and arrhythmia - the calcium connection

Repolarization alternans precedes certain types of ventricular arrhythmias and its presence may be prognostically useful, but some ventricular arrhythmias are not preceded by repolarization altemans. Nonaltemans changes of ventricular repolarization occur in patients with coronary artery disease and in subjects with congenital long QT syndrome. In animal experiments, nonaltemans repolarization lability occurs in a canine model of chronic AV block with propensity to polymorphic ventricular tachycardia, in the perfused rabbit heart exposed to IKr block, and in a murine model of catecholaminergic polymorphic ventricular tachycardia. Optical mapping experiments indicate that heterogeneity of intracellular calcium handling underlies nonaltemans repolarization variability. Detection of nonaltemans repolarization lability poses specific challenges, since signal averaging does not increase the signal to noise ratio. Nonalternans repolarization lability may be erroneously reported as repolarization altemans by non-spectral methods applied to short data segments. Additional research will be needed to determine the role of nonaltemans repolarization variability in mechanism of ventricular arrhythmias. (C) 2016 Elsevier Inc. All rights reserved.