Short QT in a cohort of 1.7 million persons: prevalence, correlates, and prognosis.
BACKGROUND
Short QT syndrome (QTc ≤ 300 ms) is a novel hereditary channelopathy linked to syncope, paroxysmal atrial fibrillation, and sudden cardiac death. However, its epidemiological features remain unsettled.


OBJECTIVE
(1) To assess the prevalence of short QT in a large population-based sample; (2) to evaluate its demographic and clinical correlates and; (3) to determine its prognosis.


METHODS
A database of 6.4 million electrocardiograms (ECGs) obtained between 1995 and 2008 among 1.7 million persons was used. An internal, population-based method for heart rate correction (QTcreg ) was used and all ECGs with QTcreg ≤300 ms were manually validated. Linked health plan databases were used for covariate and survival ascertainment.


RESULTS
Of 6,387,070 ECGs, 1086 had an ECG with machine-read QTcreg ≤300 ms. Only 4% (45/1086) were validated yielding a prevalence of 0.7 per 100,000 or 1 of 141,935 ECGs. At the person level, the overall prevalence of QTcreg ≤300 ms was 2.7 per 100,000 or 1 of 37,335. The factors independently and significantly associated with validated QTcreg ≤300 ms were age over 65 years, Black race, prior history of ventricular dysrhythmias, chronic obstructive pulmonary disease, ST-T abnormalities, ischemia, bigeminy pattern, and digitalis effect. After 8.3 years of median follow-up and relative to normal QTcreg , validated QTcreg ≤300 ms was associated after multivariate adjustment with a 2.6-fold (95% confidence interval [CI] = 1.9-3.7) increased risk of death.


CONCLUSIONS
QTcreg ≤300 ms was extraordinarily rare and was associated with significant ECG abnormalities and reduced survival.
Division of Research, Kaiser Permanente, Oakland, CA.
Carlos
C
Iribarren
Alfred D
AD
Round
Jonathan A
JA
Peng
Meng
M
Lu
Arthur L
AL
Klatsky
Jonathan G
JG
Zaroff
Taylor J
TJ
Holve
Amit
A
Prasad
Paul
P
Stang
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000453:epidemiology* / Q000503:physiopathology*; D002140:California / Q000453:epidemiology; D002648:Child; D015331:Cohort Studies; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011379:Prognosis; D012307:Risk Factors
QT interval; epidemiology; prognosis; short QT syndrome