Background: The association between QT interval and mortality has been demonstrated in large, prospective population‐based studies, but the strength of the association varies considerably based on the method of heart rate correction. We examined the QT‐mortality relationship in the Framingham Heart Study (FHS).
Methods: Participants in the first (original cohort, n = 2,365) and second generation (offspring cohort, n = 4,530) cohorts were included in this study with a mean follow up of 27.5 years. QT interval measurements were obtained manually using a reproducible digital caliper technique.
Results: Using Cox proportional hazards regression adjusting for age and sex, a 20 millisecond increase in QTc (using Bazett's correction; QT/RR1/2 interval) was associated with a modest increase in risk of all‐cause mortality (HR 1.14, 95% CI 1.10–1.18, P < 0.0001), coronary heart disease (CHD) mortality (HR 1.15, 95% CI 1.05–1.26, P = 0.003), and sudden cardiac death (SCD, HR 1.19, 95% CI 1.03–1.37, P = 0.02). However, adjustment for heart rate using RR interval in linear regression attenuated this association. The association of QT interval with all‐cause mortality persisted after adjustment for cardiovascular risk factors, but associations with CHD mortality and SCD were no longer significant.
Conclusion: In FHS, there is evidence of a graded relation between QTc and all‐cause mortality, CHD death, and SCD; however, this association is attenuated by adjustment for RR interval. These data confirm that using Bazett's heart rate correction, QTc, overestimates the association with mortality. An association with all‐cause mortality persists despite a more complete adjustment for heart rate and known cardiovascular risk factors.