OBJECTIVE: To investigate the effect of diabetes mellitus on exercise heart rate and the role of impaired heart rate in excess mortality in diabetes.
PATIENTS AND METHODS: Patients without cardiovascular disease who underwent exercise testing from September 1, 1993, through December 31, 2010, were included. Mortality was determined from Mayo Clinic records and the Minnesota Death Index. Multivariate linear regression was used to compare heart rate responses in patients with vs without diabetes. Cox regression was used to determine the effect of abnormal heart rate recovery and abnormal chronotropic index on survival.
RESULTS: A total of 21,396 patients (65.4% men) with a mean ± SD age of 51±11 years, including 1200 patients with diabetes (5.4%), were included. Patients with diabetes had a higher resting heart rate (81±14 vs 77±13 beats/min), lower peak heart rate (154±20 vs 165±19 beats/min), heart rate reserve (73±19 vs 88±19 beats/min), chronotropic index (0.86±0.22 vs 0.99±0.20), and heart rate recovery (15±8 vs 19±9 beats/min) vs patients without diabetes. There were 1362 deaths (6.4%) during a mean ± SD follow-up of 11.9±4.9 years. Adjusting for age, sex, and heart rate-lowering drug use, a chronotropic index less than 0.8 contributed significantly to risk in patients with diabetes (hazard ratio [HR], 2.21; 95% CI, 1.62-3.00; P<.001) and patients without diabetes (HR, 1.94; 95% CI, 1.71-2.20; P<.001), as did abnormal heart rate recovery (patients with diabetes: HR, 2.21; 95% CI, 1.60-5.05; P<.001; patients without diabetes: HR, 1.75; 95% CI, 1.55-1.97).
CONCLUSIONS: Patients with diabetes exhibit abnormal heart rate responses to exercise, which are independently predictive of reduced long-term survival in patients with diabetes as in patients without diabetes.
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