Abstract
Aim
The Bremen Diabetes Study is an observation study to characterise type 2 diabetic
patients at high risk for death and cardiovascular complications by routine metabolic
and cardiovascular tests. The aim of the present analysis was to evaluate the prediction
of QTc interval prolongation and/or heart rate for cardiovascular mortality in comparison
to traditional cardiovascular risk factors.
Methods
We followed 475 type 2 diabetic patients (age 55 - 75 years; 304 women, 171 men) from
a defined residential area, seen in our clinic primarily for metabolic control. Patients
with coexisting micro- or macroangiopathic complications were not excluded. Outcome
data were obtained for 423 subjects. QT intervals were measured in a 12 lead ECG and
corrected for heart rate with Fridericia's equation [QTc = QT/RR1/3].
Results
During the 5 year observation period 57 patients (13.5 %) died due to cardiovascular
causes. In multivariate analysis we found that QTc interval prolongation (p = 0.0008),
elevated heart rate (p = 0.0001), serum creatinine (p = 0.0260), smoking (p = 0.0056)
and peripheral arterial disease (p = 0.0127) at baseline were independent predictors
for cardiovascular death. The odds ratio was 2.7 (95 % CI 1.07 - 4.11) for QTc interval
prolongation (> 421 ms) and 3.3 (95 % CI 1.33 - 8.19) for elevated heart rate (> 75/min).
Conclusion
Easily established ECG criteria such as prolonged QTc time and elevated heart rate
obviously are powerful predictors of cardiovascular death in type 2 diabetic patients
and are possibly superior to the traditional cardiovascular risk factors. As heart
rate itself is an independent risk indicator, QTc time should be calculated by a formula
(e.g. Fridericia's equation) that more accurately corrects QT for heart rate than
the widely used Bazett's formula.
Key words
Type 2 diabetes - QTc interval - QTc prolongation - heart rate - cardiovascular death
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Dr. Birgit Linnemann
2nd Medical Clinic, Department of Internal Medicine, Central Hospital of Bremen-Nord
Hammersbecker Straße 228
28755 Bremen
Germany
Phone: + 4942166061301
Fax: + 49 4 21 66 06 16 79
Email: Birgit.Linnemann@zkhnord.de