Prognostic Significance of QTcInterval for Predicting Total, Cardiac, and Ischemic Heart Disease Mortality in Community-Based Cohort from Warsaw Pol-MONICA Population

Abstract

Background: QT interval in resting electrocardiogram (ECC) is a sum of ventricular depolarization and repolarization time. Its prolongation is associated with a worse prognosis for survival due to a high incidence of severe ventricular arrhythmias. Methods: The random sample of the Warsaw Pol-MONICA population consisting of 2646 men and women, aged 35–64, screened in 1984, was followed-up until 1996. All deaths and their causes were registered based on death certificate diagnosis. QT interval was measured manually in three consecutive QRST complexes in each ECG and corrected using Bazett's formula (QT corrected: QTc). For statistical analyses the mean value of 3 QTc measurements were used. To assess the relationship between QTc and mortality, the Cox proportional hazards model with stepwise selection of variables was used. Results: Out of the screened sample, 459 persons died (309 men, 150 women), 226 due to cardiovascular diseases (CVD) (162 men, 64 women), and 81 due to ischemic heart disease (IHD) (59 men, 22 women). Both men and women who died were significantly older at baseline and had significantly longer mean QTc as compared to survivors (men: 457 ms vs 446 ms, P = 0.0001; women: 469 ms vs 459 ms, P = 0.001). Among men, after adjustment for confounding variables, mean QTc was significantly associated with total and CVD mortality, and in women, with CVD and IHD mortality. The risk of death rose with an increase in QTc duration. In men, with every increase in QTc by 20 ms, the risk of all causes of death rose by 11% (95% CI: 1.04–1.18), CVD death by 9% (95% Cl: 1.01–1.19), and IHD death by 11 % (95%: 0.97–1.28). In women, the risk of all-cause death increased by 9% (95% CI: 0.98–1.21), CVD death by 21% (95% Cl: 1.02–1.43), and IHD death by 41% (95% Cl: 1.08–1.85). Conclusion: QTc interval was significantly related to all cause, cardiovascular and ischemic heart disease. The risk of death increased with longer QTc duration. A.N.E. 2000;5(4):322–329