QT interval and long-term mortality risk in the Framingham Heart Study.

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/RR(1/2) interval) was associated with a modest increase in risk of all-cause mortality (HR 1.14, 95% CI 1.10-1.18, P

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.