Optimal QT Correction Formula in Sinus Tachycardia for Identifying Cardiovascular and Mortality Risk: Findings from the Penn Atrial Fibrillation Free Study.

QT interval measures cardiac repolarization, and prolongation is associated with adverse cardiovascular outcomes and death. The exponential Bazett correction formula overestimates QT interval during tachycardia.We evaluated four methods of QT correction in individuals with sinus tachycardia for the development of coronary artery disease, heart failure and mortality.The Penn Atrial Fibrillation Free Study (PAFF) is a large cohort of patients without AF. This study examined 6,723 PAFF patients without a history of HF and with baseline sinus rate ≥100 beats per minute. Medical records were queried for index clinical parameters, incident cardiovascular events, and all-cause mortality. QT was corrected by Bazett (QT/RR(0.5)); Fridericia (QT/RR(0.33)); Framingham (QT + 0.154*(1000-RR)); and Hodges (QT+105*(1/RR-1)).Among 6,723 patients with median follow-up of 4.5 [1.9, 6.4] years, annualized cardiovascular event rate was 2.3% and annualized mortality rate was 2.2%. QT prolongation was diagnosed in 39% of the cohort by Bazett, 6.2% by Fridericia, 3.7% by Framingham, and 8.7% by Hodges. Only Hodges' formula was an independent risk marker for death across the range of QT values [HR highest tertile: 1.26, 95% CI (1.03-1.55)].Although all correction formulas demonstrated an association between QTc values and cardiovascular events, only the Hodges formula identified one-third of individuals with tachycardia that are at higher risk for all-cause mortality. Further, Bazett's correction overestimates the number of patients with a prolonged QT and was not associated with mortality. Future work may validate these findings and result in changes to automated algorithms for QT interval assessment.