Assessment of QT interval and QT dispersion for prediction of all-cause and cardiovascular mortality in American Indians: The Strong Heart Study.
BACKGROUND
Both a prolonged QT interval and increased QT interval dispersion (QTD) have been proposed as surface ECG markers of vulnerability to ventricular arrhythmias and potential predictors of mortality.


RESULTS
The predictive values of QT prolongation and QTD were assessed in 1839 participants in the Strong Heart Study, a prospective study of cardiovascular disease in American Indians. ECGs were acquired at 250 Hz; QT intervals were measured by computer in all 12 leads and corrected for heart rate (QTc) by use of Bazett's formula. QTD was calculated as the difference between the maximum and minimum QTc. After a mean follow-up of 3.7+/-0.9 years, there were 188 deaths from all causes, including 55 cardiovascular deaths. In univariate Cox analyses, prolonged QTc and increased QTD were significant predictors of all-cause mortality (chi(2)=53.0, P<0.0001; chi(2)=11.3, P=0.0008) and cardiovascular mortality (chi(2)=14.7, P=0.0001; chi(2)=26.5, P<0.0001). In multivariate Cox regression analyses controlling for risk factors, QTc remained a strong predictor of all-cause mortality (chi(2)=16.5, P<0.0001) and a weaker predictor of cardiovascular mortality (chi(2)=5.8, P=0.016); QTD remained a significant predictor of cardiovascular mortality only (chi(2)=12.5, P=0.0004).


CONCLUSIONS
These findings support the value of computerized measurements of QTc and QTD in noninvasive risk stratification and suggest that these surface ECG variables may reflect different underlying abnormalities of ventricular repolarization.
Okin
P M
PM
Division of Cardiology, Department of Medicine, Cornell Medical Center, New York, NY 10021, USA. pokin@mail.med.cornell.edu
Devereux
R B
RB
Howard
B V
BV
Fabsitz
R R
RR
Lee
E T
ET
Welty
T K
TK
D000368:Aged; D000704:Analysis of Variance; D001145:Arrhythmias, Cardiac / Q000401:mortality / Q000503:physiopathology; D002318:Cardiovascular Diseases / Q000401:mortality*; D002423:Cause of Death; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate; D006801:Humans; D007198:Indians, North American; D008133:Long QT Syndrome / Q000401:mortality* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009825:Oklahoma; D011237:Predictive Value of Tests; D012044:Regression Analysis; D012307:Risk Factors; D016019:Survival Analysis