How is QRS duration related to CV morbidity and mortality in asymptomatic patients with mild-to-moderate aortic stenosis (AS)? Anders M. Greve, MD, and colleagues sought to answer that question using data from the SEAS (Simvastatin Ezetimibe in Aortic Stenosis) study.

Researchers used pre-specified analyses of prospectively collected SEAS and SEAS electrocardiographic substudy data to examine whether QRS duration is an independent risk factor for sudden cardiac death (SCD), overall CV death, CV morbidity, aortic valve replacement (AVR), or all-cause mortality in asymptomatic patients with AS.

Baseline electrocardiograms and QRS were assessed in 1,542 patients (942 men and 600 women), who were followed for approximately 4 years. Investigators found patients with QRS duration <85 msec had an SCD rate of approximately 0.2% and an overall CV death rate of 0.8%.

For those with QRS duration of 85-99 msec, the SCD rate was 0.5% and the CV death rate was 1.2%; for patients with QRS duration of ≥100 msec, SCD rate was 1.3% and CV death rate was 2.3% compared with 0.6% for SCD and 1.1% for CV death in those with left bundle branch block (LBBB). (See accompanying figure for SCD rates.)

“First, longer QRS duration is associated with risks of SCD and overall CV death, independent of clinical- and echocardiographic covariates. Second, among patients with QRS duration ≥120 msec, only those with LBBB or combined RBBB and left anterior fascicular block carry an increased risk of CV events (Click on figure to the right),” Dr. Greve and co-authors write. Although the exact mechanisms aren’t clear, the investigators hypothesize that correlation “may reflect associations of increased QRS duration with: 1) adverse LV response to increased afterload above the changes in LV mass per se; 2) myocardial scarring due to chronic subendocardial ischemia and fibrosis, further supported by the association with incident MI; and 3) a higher threshold for termination of spontaneously occurring ventricular tachycardia in the presence of longer QRS duration.”

The authors suggest that physicians consider QRS duration and morphology when weighing “watchful waiting” versus intervention in patients with asymptomatic AS.

Reference

1. Greve AM, et al. J Am Coll Cardiol. 2012;59:1142-9.

Keywords: Tachycardia, Ventricular, Bundle-Branch Block, Risk Factors, Electrocardiography, Death, Sudden, Cardiac, Echocardiography

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