Corrected QT variability in serial electrocardiograms in long QT syndrome: the importance of the maximum corrected QT for risk stratification.
OBJECTIVE
We evaluated the incremental prognostic information provided by multiple corrected QT (QTc) measurements on serial electrocardiograms (ECGs) in patients with the inherited long QT syndrome (LQTS).


BACKGROUND
A baseline QTc of > or =500 ms has been shown to be associated with increased risk of cardiac events among LQTS patients. However, the value of QTc measurements on follow-up ECGs in risk assessment has not been determined.


METHODS
The risk of a first LQTS-related cardiac event during adolescence was assessed in 375 patients enrolled in the International LQTS Registry for whom serial follow-up ECGs were recorded before age 10.


RESULTS
The mean +/- SD difference between the minimum and maximum QTc values on serial ECGs recorded in study patients was 47 +/- 40 ms. The maximum QTc interval recorded before age 10 was the strongest predictor of cardiac events during adolescence (adjusted hazard ratio [HR] = 2.74; p < 0.001). Other follow-up QTc measures, including the baseline, the mean, and the most recent QTc interval recorded before age 10, were less significant risk factors. After adjusting for the maximum QTc value during follow-up, no significant association remained between the baseline QTc value and the risk of subsequent cardiac events (HR = 1.04; p = 0.91).


CONCLUSIONS
In LQTS patients, there is a considerable variability in QTc measures in serial follow-up ECGs. The maximum QTc interval provides incremental prognostic information beyond the baseline measurement. We suggest that risk stratification in LQTS patients should include follow-up ECG data.
Goldenberg
Ilan
I
Cardiology Division, Department of Medicine, University of Rochester Medical Center, Rochester, New York 14642, USA. ilan.goldenberg@heart.rochester.edu
Mathew
Jehu
J
Moss
Arthur J
AJ
McNitt
Scott
S
Peterson
Derick R
DR
Zareba
Wojciech
W
Benhorin
Jesaia
J
Zhang
Li
L
Vincent
G Michael
GM
Andrews
Mark L
ML
Robinson
Jennifer L
JL
Morray
Brian
B
D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006323:Heart Arrest / Q000209:etiology; D006801:Humans; D008133:Long QT Syndrome / Q000145:classification* / Q000150:complications* / Q000151:congenital / Q000473:pathology; D008297:Male; D011379:Prognosis; D018570:Risk Assessment; D013575:Syncope / Q000209:etiology