Heart Rate Turbulence Can Predict Cardiac Mortality Following Myocardial Infarction in Patients With Diabetes Mellitus

BACKGROUND: Previous studies have described the clinical utility of heart rate turbulence (HRT) as an autonomic predictor in risk-stratifying patients after myocardial infarction (MI). Some reports showed that diabetes mellitus (DM) affects the prognostic value of autonomic markers. We assessed the utility of HRT as a risk marker in post-MI patients with DM and without DM. METHODS: We prospectively enrolled 231 consecutive DM patients and 300 non-DM patients after acute MI. HRT was measured using an algorithm based on 24-hour Holter electrocardiograms (ECGs), assessing 2 parameters: turbulence onset (TO) and turbulence slope (TS). HRT was considered positive when both TO ≥0% and TS ≤2.5 ms/R-R interval were met. The endpoint was defined as cardiac mortality. RESULTS: Of patients with DM, 9 patients (4%) were not utilized for HRT assessment because of frequent ventricular contractions or presence of atrial fibrillation. Forty-two of 222 patients (19%) were HRT positive. During follow-up of 876 ± 424 days, 26 patients (22%) reached the endpoint. Several factors including left ventricular ejection fraction (LVEF), renal dysfunction, documentation of nonsustained ventricular tachycardia (VT), and a HRT-positive outcome had significant association with the endpoint. Multivariate analysis determined that renal dysfunction and a positive HRT outcome had significant value with a hazard ratio (HR) of 4.7 (95%CI, 1.9-11.5; P = 0.0008) and 3.5 (95%CI, 1.4-8.8; P = 0.007), respectively. In non-DM patients, only a positive HRT outcome had significant value. CONCLUSIONS: This study reveals that HRT detected by 24-hour Holter ECG can predict cardiac mortality in post-MI patients whether DM is present or not.