Objective: Long-term diabetes is associated with excess morbidity and mortality, and cardiovascular autonomic neuropathy and QTc interval abnormalities are both predictive of early cardiovascular death in diabetes. We aimed to investigate the effect of these risk factors in a large cohort of type 1 diabetic patients followed prospectively for 10 years.
Material and methods: Three-hundred-and-ninety-one type 1 diabetic mellitus patients (240 M and 151 F, age 41.8 years +/- 9.9 (mean +/-SD), duration of DM 27.3 years +/- 8.2) were followed in an outpatient setting.
Results: Patients with decreased heart rate variability had an excess overall mortality that diminished after adjusting for conventional cardiovascular risk factors; hazard ratio 2.5 (0.9-6.8; p = 0.071) compared to patients with normal heart rate variability. Likewise, prolonged QTc interval was associated with premature death with an adjusted hazard ratio of 2.3 (1.3-4.0; p = 0.005). In a combined analysis, patients with abnormal values for heart rate variability and QTc had a poorer prognosis compared to patients with normal test values for both parameters (adjusted hazard ratio 6.7 (1.8-25; p = 0.005)). Of the 34 patients with both test values abnormal, 15 died and 14 of these from cardiovascular causes.
Conclusions: We conclude that combined abnormality in heart rate variability and QTc is a strong predictor of mortality in type 1 diabetes independently of conventional risk factors. These results have implications for future screening and treatment programmes for cardiovascular disease in type 1 diabetes.