Comparison of Inducible and Spontaneous Ventricular Tachycardia in Defibrillator Recipients Following Myocardial Infarction

Abstract

Background: We assessed the cycle length (CL) of ventricular tachycardia (VT) induced at electrophysiology study (EPS) early post-MI with spontaneous VT at follow up in implantable-cardioverter defibrillator (ICD) recipients. Methods: Consecutive STEMI patients with left ventricular ejection fraction (LVEF) ≤40% underwent EPS as part of a study protocol targeting early (within 40 days) prevention of sudden cardiac death (SCD). The CL of induced VT at EPS was compared with first spontaneous VT and subsequent VT in ICD recipients at follow up. Secondary endpoints included mortality, sudden cardiac death (SCD) and cardiac arrest. Results: EPS performed early post-MI in 403 patients was negative in 68.5% (n = 276) and positive in 31.5% (n = 127). In patients with a positive EPS, induced monomorphic VT had mean CL 229 ± 29 milliseconds. Primary prevention ICD was implanted in 120/127 patients with a positive EPS. In EPS positive patients with an ICD, 33% had an appropriate activation due to either VF (n = 5) or VT (n = 35) mean CL 308 ± 47 milliseconds at mean 3.4 ± 2.7 years post-STEMI. In individual patients the induced VT CL at EPS did not correlate with first spontaneous VT CL (r = 0.09, p = 0.60) but instead the VT CL lengthened with time post-MI (r = 0.481, p < 0.001). Total mortality occurred in 15.7% and 5.1% of EPS positive and negative patients, respectively (p = 0.001). Conclusions: In patients post-MI with LVEF ≤40% and inducible VT at early EPS, the first episode of spontaneous VT at follow up in ICD recipients was significantly slower to what was induced. This is potentially related to the myocardial remodelling process post-MI.