Evaluation of abnormal heart-rate recovery after exercise testing in patients with diabetes mellitus: correlation with myocardial SPECT and chronotropic parameters.

OBJECTIVE: Diabetes is associated with abnormal function of the autonomic nervous system, while autonomic dysfunction is related to attenuated heart-rate recovery (HRR) after exercise testing. The purpose of this study was to test whether HRR could be a useful index of myocardial ischaemia in patients suffering from diabetes mellitus.

METHODS: We included 206 consecutive patients in this study and excluded patients whose HRR value or the myocardial perfusion imaging could have been influenced by factors other than myocardial ischaemia. The value of HRR was defined as the decrease in the heart rate from peak exercise to 1 min after the termination of the exercise. All patients underwent SPECT myocardial perfusion imaging, combined with exercise testing and we calculated the summed stress score (SSS), summed rest score (SRS) and summed difference score (SDS) indexes.

RESULTS: Sixty patients had abnormal HRR value. A significant correlation was found between HRR 1 min after exercise and SSS (r=-0.64, P<0.001), SDS (r=0.56, P<0.001) and chronotropic variables. Patients with abnormal HRR value, had a higher frequency of other risk factors (besides diabetes) for CAD, were mostly taking cardioactive medications, had lower efficiency during treadmill testing, and presented more pathologic findings on the scintigram.

CONCLUSIONS: Our results suggest that myocardial ischaemia, as it is mainly assessed by myocardial perfusion imaging, has an important correlation with HRR in diabetic patients. HRR value 1 min after exercise may be considered as a useful index of the severity of myocardial ischaemia, in this cohort of patients.