Circ Rep. 2026 Jun 23;8(8):1220-1227. doi: 10.1253/circrep.CR-26-0138. eCollection 2026 Aug 10.
ABSTRACT
BACKGROUND: The corrected QT interval (QTc) is essential for long QT syndrome (LQTS) screening. QTc values change with growth, and sex differences emerge at puberty. However, few longitudinal studies have assessed QTc changes across childhood and adolescence, and age- and sex-specific QTc cut-offs using Bazett's and Fridericia's formulas (QTcB and QTcF, respectively) near the onset of puberty have not been established.
METHODS AND RESULTS: We retrospectively analyzed electrocardiograms from school-based screening. QT and RR intervals were measured manually, and QTcB and QTcF were calculated in 4th graders (n=2,753); subsets were additionally assessed in 1st graders (n=1,289) and 7th graders (n=1,351). Longitudinal changes in QTc were evaluated. QTc cut-offs for LQTS screening were determined using both the 99.5th percentile and histogram assessment. No significant sex difference in mean QTcB and QTcF values was found in 1st graders. These values in 4th graders were significantly shorter in males than in females (QTcB: 374±20 vs. 378±21 ms; QTcF: 389±23 vs. 395±24 ms; P<0.001). QTcB cut-offs (males/females) for 1st, 4th, and 7th graders were 453/448, 449/462, and 463/462 ms, respectively. The QTcF cut-off values (males/females) for 1st, 4th, and 7th graders were 425/436, 438/438, and 440/443 ms, respectively.
CONCLUSIONS: Sex differences in QTc emerge in the 4th grade. Age- and sex-specific QTc cut-offs are required for screening in children and adolescents.
PMID:42577475 | PMC:PMC13454668 | DOI:10.1253/circrep.CR-26-0138