Time Dependence of Ventricular Tachyarrhythmias After Myocardial Infarction: A MADIT-CRT Substudy

Objectives The purpose of this study was to assess the relationship between the time since a myocardial infarction (MI) and the risk of ventricular tachyarrhythmic events (VTEs) in patients with left ventricular dysfunction and mild symptoms of heart failure. Background Patients with left ventricular dysfunction after MI are at high risk for VTEs. Methods Ventricular tachycardia (VT), ventricular fibrillation (VF), or death as a function of time since MI was assessed in 693 patients enrolled in the MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy). Patients were categorized as those with a period of <3 years since an MI (lowest quartile, n = 172) versus those with a period of ≥3 years since an MI (n = 521). Risk of VT/VF or death was compared. Results Cumulative probability of VT/VF or death was significantly higher among patients in the highest quartile of time since an MI compared with those in the lowest quartile (41% vs. 22%, p = 0.015). Multivariate analysis showed that in patients with left bundle branch block (LBBB), those with a period of ≥3 years since an MI had a significantly higher risk of VT/VF or death (hazard ratio: 2.33; 95% confidence interval: 1.43 to 3.80; p = 0.001) and a higher risk of VT/VF (hazard ratio: 3.18; 95% confidence interval: 1.71 to 5.90; p < 0.001) compared with patients with a period of <3 years since an MI. These findings were consistent when the time since an MI was analyzed in a continuous fashion. A significant relationship between the time since an MI and outcomes was not observed in patients with non-LBBB. Conclusions Among post-MI patients with left ventricular dysfunction and LBBB, the risk of VTEs is directly related to the time since an MI occurred.