Prognostic impact of prolonged ventricular repolarization in hypertension

Abstract

Background: QT interval prolongation on the surface electrocardiogram (ECG) predicts cardiovascular complications in high-risk subjects, but its prognostic role in uncomplicated hypertension has been understudied.

Methods: For up to 13 years (average, 5.3 years), we followed up 2110 white patients with initially untreated essential hypertension (mean +/- SD age, 49 +/- 12 years; 55% men) without prevalent cardiovascular or renal disease who underwent 12-lead ECG before therapy. We excluded patients with ECG abnormalities including ischemia, necrosis, complete bundle branch block, atrial fibrillation, arrhythmias, and ventricular preexcitation.

Results: Heart rate-corrected QT interval (QTc) showed a weak but significant direct association with systolic blood pressure (r = 0.07; P<.001), diastolic blood pressure (r = 0.11; P<.001), and Cornell voltage (r = 0.06; P = .006). During follow-up, 84 patients developed new-onset ischemic heart disease (0.75 event per 100 patient-years). After adjustment (Cox model) for the effects of age, sex, diabetes mellitus, serum cholesterol level, serum creatinine level, smoking, left ventricular hypertrophy, and 24-hour systolic blood pressure, patients with a prolonged QTc (>or=450 milliseconds in women and >or=440 milliseconds in men) had a nearly 2-fold increase in risks of coronary events (hazard ratio, 1.95; 95% confidence interval, 1.12-3.42; P = .02) and cardiovascular death (hazard ratio, 2.05; 95% confidence interval, 1.03-4.37; P = .04). Coronary heart disease risk was independently higher by 33% (95% confidence interval, +7% to +66%; P = .01) for each 32-millisecond increase in QTc.

Conclusions: Prolonged ventricular repolarization is a risk factor for ischemic heart disease and cardiovascular mortality in subjects with uncomplicated hypertension. Its prognostic significance adds to that of several traditional cardiovascular risk factors, including left ventricular hypertrophy.