Objective: The prognostic value of prolonged ventricular repolarization in patients with resistant hypertension is unknown. The aim of this prospective study was to investigate the usefulness of electrocardiographic QT-interval parameters as predictors of cardiovascular morbidity and mortality.
Methods: At baseline, 538 resistant hypertensive patients had five QT-interval components measured in standard 12-lead ECGs: maximum QRS, QTpeak, QTend, JT and Tpeak-to-end-interval durations. Primary endpoints were a composite of fatal and nonfatal cardiovascular events, all-cause and cardiovascular mortalities. Multiple Cox regression assessed the associations between QT-interval parameters and subsequent endpoints.
Results: After a median follow-up of 4.8 years, 69 (12.8%) patients died, 46 from cardiovascular causes, and 107 (19.9%) fatal or nonfatal cardiovascular events occurred. After adjustment for several traditional risk factors, including 24-h ambulatory systolic blood pressure, an increment of 1 SD (35 ms) in QTcend-interval was associated with hazard ratios of 1.38 (1.15–1.67), 1.51 (1.16–1.98) and 1.30 (1.03–1.64), respectively, for the composite endpoint, cardiovascular mortality and all-cause mortality. Further adjustment for left ventricular hypertrophy attenuated the relative risks, but they remained significant for cardiovascular mortality (1.45, 1.07–1.97) and for the composite endpoint (1.35, 1.11–1.66). After full adjustment, a prolonged QTcend-interval (≥460 ms) conferred a 1.7-fold (1.1–2.6) higher risk of having a future fatal or nonfatal cardiovascular event. No other QT-interval component added further prognostic information to QTcend-interval duration.
Conclusions: Prolonged ventricular repolarization is a risk marker for cardiovascular morbidity and mortality in patients with resistant hypertension, over and beyond traditional cardiovascular risk factors, including ambulatory blood pressure and left ventricular hypertrophy.
Department of Internal Medicine, University Hospital Clementino Fraga Filho, Medical School, Federal University of Rio de Janeiro, Brazil
Received 6 September, 2008
Revised 14 November, 2008
Accepted 19 December, 2008
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