Introduction: Patients with diabetes mellitus (DM) have an unfavorable prognosis after myocardial infarction (MI), partially due to a higher risk of sudden cardiac death (SCD). QT dynamicity is an independent predictor of SCD in post-MI patients. However, the effects of diabetes on QT dynamicity in patients with MI have not been described.
Methods: We studied 468 survivors of MI (67 with DM) from the population-based MONICA registry (KORA Family Heart Study), Augsburg, Germany, by standardized questionnaire, anthropometry, electrocardiogram (ECG), 30-minute-Holter-ECG-recordings and echocardiography. In addition, 422 siblings without prior MI (22 with DM) were studied by the same protocol.
Results: Among post-MI patients, the QT/RR slope was significantly steeper in diabetics than in nondiabetics (0.096 +/- 0.057 vs 0.077 +/- 0.045; P = 0.002). Likewise, among siblings without MI, the QT/RR slope was steeper in diabetics than in nondiabetics (0.104 +/- 0.053 vs 0.080 +/- 0.042; P = 0.008). The association of DM with steeper QT/RR slope remained significant in multivariate models in post-MI patients (beta: -0.14; P = 0.004) as well as in individuals without MI (beta: -0.10; P = 0.047).
Conclusions: In a large population of survivors of MI and unaffected siblings, patients and siblings presenting with DM exhibited an abnormal QT rate-dependence, compared with individuals without DM in both groups. Thus, diabetes itself may be a major determinant of ventricular arrhythmias, independently of a previous MI. These observations might in part explain the higher incidence of sudden cardiac death and ventricular arrhythmias in patients with DM.