QTc interval and resting heart rate as long-term predictors of mortality in type 1 and type 2 diabetes mellitus: a 23-year follow-up.
OBJECTIVE
We evaluated the association of QT interval corrected for heart rate (QT(c)) and resting heart rate (rHR) with mortality (all-causes, cardiovascular, cardiac, and ischaemic heart disease) in subjects with type 1 and type 2 diabetes.


METHODS
We followed 523 diabetic patients (221 with type 1 diabetes, 302 with type 2 diabetes) who were recruited between 1974 and 1977 in Switzerland for the WHO Multinational Study of Vascular Disease in Diabetes. Duration of follow-up was 22.6 +/- 0.6 years. Causes of death were obtained from death certificates, hospital records, post-mortem reports, and additional information given by treating physicians.


RESULTS
In subjects with type 1 diabetes QT(c), but not rHR, was associated with an increased risk of: (1) all-cause mortality (hazard ratio [HR] 1.10 per 10 ms increase in QT(c), 95% CI 1.02-1.20, p = 0.011); (2) mortality due to cardiovascular (HR 1.15, 1.02-1.31, p = 0.024); and (3) mortality due to cardiac disease (HR 1.19, 1.03-1.36, p = 0.016). Findings for subjects with type 2 diabetes were different: rHR, but not QT(c) was associated with mortality due to: (1) all causes (HR 1.31 per 10 beats per min, 95% CI 1.15-1.50, p < 0.001); (2) cardiovascular disease (HR 1.43, 1.18-1.73, p < 0.001); (3) cardiac disease (HR 1.45, 1.19-1.76, p < 0.001); and (4) ischaemic heart disease (HR 1.52, 1.21-1.90, p < 0.001). Effect modification of QT(c) by type 1 and rHR by type 2 diabetes was statistically significant (p < 0.05 for all terms of interaction).


CONCLUSIONS
QT(c) is associated with long-term mortality in subjects with type 1 diabetes, whereas rHR is related to increased mortality risk in subjects with type 2 diabetes.
Stettler
C
C
Division of Endocrinology and Diabetes, University of Bern, Inselspital, CH-3010, Bern, Switzerland.
Bearth
A
A
Allemann
S
S
Zwahlen
M
M
Zanchin
L
L
Deplazes
M
M
Christ
E R
ER
Teuscher
A
A
Diem
P
P
D000328:Adult; D000368:Aged; D002318:Cardiovascular Diseases / Q000209:etiology / Q000503:physiopathology; D003922:Diabetes Mellitus, Type 1 / Q000150:complications / Q000401:mortality* / Q000503:physiopathology*; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000401:mortality* / Q000503:physiopathology*; D018450:Disease Progression; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D053208:Kaplan-Meier Estimate; D008133:Long QT Syndrome / Q000150:complications / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models