Impact of left ventricular hypertrophy on QT prolongation and associated mortality

Abstract

Background: QT prolongation on electrocardiogram (ECG) is a risk marker of ventricular arrhythmias and all-cause mortality. Left ventricular hypertrophy (LVH) on ECG is also associated with poor outcome. Patients satisfying ECG voltage criteria for LVH frequently show concomitant QT prolongation.

Objective: This study aimed to explore the impact of marked QT prolongation on all-cause mortality in patients copresenting with LVH voltage criteria and prolonged QT on ECG.

Methods: We evaluated 3364 ECGs with corrected QT (QTc) interval ≥460 ms detected by Mayo Clinic's QT alert system from November 2010 through June 2011. Every ECG with QTc interval ≥460 ms was evaluated for the presence of LVH voltage criteria by using Sokolow-Lyon voltage, Cornell voltage, and Cornell product.

Results: Concomitant LVH voltage criteria were present in 181 of 3364 ECGs (5.3%) with QTc interval ≥460 ms. Mortality during a follow-up period of 217 ± 184 days was 13% (23 of 181). Independent of age and hypertension, the QTc interval predicted mortality in patients with LVH voltage criteria (hazard ratio 1.31 per 10-ms increase; 95% confidence interval 1.09-1.58; P < .01). Patients with LVH voltage criteria and QTc interval ≥500 ms had highest mortality (log rank, P < .001).

Conclusion: The QTc interval was an independent predictor of mortality in patients with concomitant LVH voltage and prolonged QTc interval on ECG. Mortality was highest in those with QTc interval ≥500 ms. QT prolongation on ECGs with concomitant LVH voltage criteria should not be regarded as a harmless byproduct of LVH, but should be used as a significant marker of increased mortality risk similar to that in patients without LVH voltage criteria.

Keywords: Electrocardiogram; Left ventricular hypertrophy; Mortality; QTc.