The influence of cardiac rehabilitation on heart rate variability indices in men with type 2 diabetes and coronary artery disease

The study evaluated the influence of cardiac rehabilitation (CR) on heart rate variability (HRV) in men with coronary artery disease (CAD) with and without diabetes. Method: The study population included 141 male CAD patients prospectively and consecutively admitted to an outpatient comprehensive CR program. Twenty-seven patients with type-2 diabetes were compared with 114 males without diabetes. The participants performed a 45-min cycle ergometer interval training alternating 4-min workload and a 2-min active restitution three times a week for 8 weeks. The training intensity was adjusted so that the patient's heart rate achieved the training heart rate calculated according to the Karvonen formula. At the baseline and after 8 weeks, all the patients underwent the HRV assessment. Results: HRV indices in the patients with diabetes were significantly lower as compared to the patients without diabetes in SDNN, TP, LF parameters, both at the baseline and after 8 weeks of CR. After 8 weeks of CR, a significant improvement of TP, SDNN, pNN50% and HF occurred in the patients without diabetes, whereas in the patients with diabetes only HF component improved significantly. Conclusions: As regards HRV indices, CR seems to be less effective in patients with CAD and type-2 diabetes.