Impact of left ventricular hypertrophy on QT prolongation and associated mortality

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 OT (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 SokolowLyon 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 CITc 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.