Abstract 4137342: Prolonged Bazett’s corrected QT interval is associated with cardiovascular events and sudden death in Japanese patients with cardiovascular risk

Background: QT durations are sex-dependent, with women having longer QT durations than men. In addition to congenital long-QT syndrome, prominent QTc prolongation is a risk for sudden death. There are several correction formulas for the QTc interval, but the association between the QTc interval and cardiovascular events by type of correction in patients at cardiovascular risk remains unclear. Hypothesis: Prolonged QTc duration is associated with cardiovascular events and sudden death in patients at high cardiovascular risk. Methods: We enrolled 4,654 subjects from the Cardiovascular Prognostic Coupling Study in Japan (Coupling Registry), who had one or more cardiovascular risk factors. We used two different definitions of QT prolongation: Bazett’s corrected QT interval (QTcB) and Fridericia’s corrected QT interval (QTcF). QTc was divided into quartiles by gender, and quartile associations with the primary endpoint (composite cardiovascular events: cardiovascular death, nonfatal myocardial infarction/stroke) and secondary endpoint (sudden death) were compared. Results: QTc duration in females (QTcB: median 428 [IQR 414–444] ms, QTcF 422 [IQR 409–436] ms) was slightly longer than that in males (QTcB: median 419 [IQR 405–435] ms and QTcF 415 [IQR 402–430], both p<0.001). The mean follow-up period was 53 ± 17 months, during which 159 primary endpoints and 14 secondary endpoints occurred. The longest QTcB group (Q4: ≥ 435 ms in men, ≥ 444 ms in women) had significantly more cardiovascular events than the other quartiles (vs. Q1: p=0.016, vs. Q2: p=0.037, and vs. Q3 p=0.141), and sudden death was more common than in Q2 and Q3 (vs. Q2 0.003, vs. Q3: p=0.032). On the other hand, the longest QTcF group (Q4) (≥430 ms for men, 436 ms for women) had significantly more cardiovascular events than the Q1 and Q2 groups but not the Q3 group (vs. Q1: p=0.016, vs. Q2: p=0.037, and vs. Q3: p=0.141); sudden death was not significantly different among quartiles (all P>0.05). Conclusions: In Japanese patients at cardiovascular risk, prolonged QTcB was associated with cardiovascular events as well as sudden death.