Assessment of QT intervals and prevalence of short QT syndrome in Japan.
BACKGROUND
Long QT syndrome causes ventricular tachyarrhythmias and sudden death. Recently, a short QT interval has also been shown to be associated with an increased risk of tachyarrhythmia and sudden death. However, the prevalence of short QT syndrome is not well-known.


OBJECTIVE
The aim of this study was to assess the distribution of corrected QT intervals (QTc) and prevalence of short QT syndrome.


METHODS
This study comprised 12,149 consecutive subjects who received a consultation at Kanazawa University Hospital, Kanazawa, Japan, and had an electrocardiogram (ECG) between February 2003 and May 2004. Of these subjects, 1,165 subjects were excluded because of inappropriate ECGs, while the remaining 10,984 subjects had their last-recorded ECGs analyzed.


RESULTS
The QTc values showed a nearly normal distribution (408 +/- 25 msec(1/2)), and were significantly longer in females (412 +/- 24 msec(1/2)) than in males (404 +/- 25 msec(1/2)) (p < 0.05). Among 5,511 males, 69 subjects (1.25%) exhibited QTc < 354 msec(1/2) (2 standard deviations [SDs] below the mean in males), and among 5,473 females, 89 subjects (1.63%) exhibited QTc < 364 msec(1/2) (2 SDs below the mean in females). Only 3 subjects (0.03% in all subjects and 0.05% in males) exhibited QTc < 300 msec(1/2), however, none had clinical symptoms of short QT syndrome.


CONCLUSIONS
Short QT syndrome may be very rare.
Funada
Akira
A
Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan. a-funada@e-mail.jp
Hayashi
Kenshi
K
Ino
Hidekazu
H
Fujino
Noboru
N
Uchiyama
Katsuharu
K
Sakata
Kenji
K
Masuta
Eiichi
E
Sakamoto
Yuichiro
Y
Tsubokawa
Toshinari
T
Yamagishi
Masakazu
M
D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D016757:Death, Sudden, Cardiac / Q000453:epidemiology; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011379:Prognosis; D012189:Retrospective Studies; D013577:Syndrome