New age- and sex-specific criteria for QT prolongation based on rate correction formulas that minimize bias at the upper normal limits.
BACKGROUND
Existing formulas for rate-corrected QT (QTc) commonly fail to properly adjust the upper normal limits which are more critical than the mean QTc for evaluation of prolonged QT. Age- and sex-related differences in QTc are also often overlooked. Our goal was to establish criteria for prolonged QTc using formulas that minimize QTc bias at the upper normal limits.


RESULTS
Strict criteria were used in selecting a study group of 57,595 persons aged 5 to 89 years (54% women) and to exclude electrocardiograms (ECG) with possible disease-associated changes. Two QT rate adjustment formulas were identified which both minimized rate-dependency in the 98 th percentile limits: QTcmod, based on an electrophysiological model (QTcMod = QTx(120 + HR)/180)), and QTcLogLin, a power function of the RR interval with exponents 0.37 for men and 0.38 for women. QTc shortened in men during adolescence and QTcMod became 13 ms shorter than in women at age 20-29 years. The sex difference was maintained through adulthood although decreasing with age. The criteria established for prolonged QTc were: Age < 40 years, men 430 ms, women 440 ms; Age 40 to 69, men 440 ms, women 450 ms; Age ≥ 70 years, men 455 ms, and women 460 ms.


CONCLUSIONS
Sex difference in QTc originates from shortened QT in adolescent males. Upper normal limits for QTc vary substantially by age and sex, and it is essential to use age- and sex-specific criteria for evaluation of QT prolongation.
Division of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem, NC, USA. Electronic address: pentti.rautaharju@gmail.com.
Pentti M
PM
Rautaharju
Cardiology Division, University of Utah, Salt Lake City, UT, USA.
Jay W
JW
Mason
Cardiology Division, University of Rochester, NY, USA.
Toshio
T
Akiyama
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology* / Q000502:physiology*; D015982:Bias; D002648:Child; D002675:Child, Preschool; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000453:epidemiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012727:Sex Characteristics; D055815:Young Adult
Aging; Normal standards; QT prolongation; Sex differences