Long-term prognostic value of heart-rate recovery after treadmill testing in patients with diabetes mellitus

Background: Heart-rate recovery (HRR) is considered to be an independent predictor of cardiac and all-cause mortality. We examined the long-term prognostic value of HRR in patients suffering from diabetes mellitus. Methods: In this study, we included 258 consecutive patients. Patients whose HRR value or myocardial perfusion imaging could have been influenced by factors other than myocardial ischaemia, were excluded. 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. Cardiovascular death and non-fatal myocardial infarction were considered as hard cardiac events, while late revascularization procedures as soft events. Cox proportional-hazard models were applied to evaluate the association between HRR and the investigated outcome. Results: During the follow-up period (30.8 +/- 6.9 months), hard cardiac events occurred in 21 (8%) patients (15 with abnormal HRR value, p<0.001), while 35 (14%) patients underwent revascularization (31 with abnormal HRR value, p<0.001). Considering it as a continuous variable, HRR was a strong predictor for both hard cardiac (coefficient=-0.41, SE=0.052, p<0.001) and soft cardiac events (coefficient=-0.63, SE=0.058, p<0.001). After adjustments were made for potential confounders, including scintigraphic variables, abnormal HRR remained an independent predictor for hard and soft cardiac events (p<0.001). Conclusion: Our results suggest that among patients with diabetes, a decreased HRR is a significant independent predictor of hard and soft cardiac events. (C) 2008 Elsevier Ireland Ltd. All rights reserved.