Referenced in: none

Automatically associated channels: Nav1.5 , Slo1

Title: Early repolarization in mice causes overestimation of ventricular activation time by the QRS duration.

Authors: Bas J Boukens, Mark G Hoogendijk, Arie O Verkerk, Andre Linnenbank, Peter van Dam, Carol-Ann Remme, Jan W Fiolet, Tobias Opthof, Vincent M Christoffels, Ruben Coronel

Journal, date & volume: Cardiovasc. Res., 2013 Jan 1 , 97, 182-91

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/22997159

Abstract
Transgenic mice are frequently used to investigate the role of genes involved in cardiac conduction. The QRS duration calculated from the electrocardiogram (ECG) is a commonly used measure for ventricular conduction time. However, the relation between ventricular activation and QRS duration calculated from a mouse surface ECG is not well understood. We aim to relate ventricular activation and repolarization patterns with the mouse ECG.Ventricular activation and repolarization patterns generated by high-density optical mapping and a six-lead pseudo-ECG were compared in isolated mouse hearts. In addition, mouse ECGs were simulated in silico. Right-ventricular activation ends later than left-ventricular activation. Final activation coincided with the end of the QRS complex in leads III and aVF, but not in leads I, II, aVR, and aVL. The pattern of early repolarization (at 20% of repolarization, RT20) but not of RT50 or RT80 followed the activation pattern. After sodium channel blockade by ajmaline, total ventricular activation time increased by 10.0 ms, whereas QRS duration increased by only 2.1 ms. In mice carrying a mutation in Scn5a (1798insD), ventricular activation ended after the end of the QRS complex (12.9 ± 0.1 vs. 10.8 ± 0.3).In the mouse, ventricular myocardium activation and early repolarization waves are simultaneously present. This hampers unequivocal interpretation of the duration of the QRS complex as a measure of ventricular activation duration, especially when conduction is slowed. Under these conditions mapping of local activation and repolarization patterns is required for correct interpretation of the ECG.