title: Frequency and Implications of Ischemia Prior to Ventricular Tachyarrhythmia in Patients Treated With a Wearable Cardioverter Defibrillator Following Myocardial Infarction.
abstract: BACKGROUND
  Autopsy studies imply that recurrent myocardial infarction (MI) accounts for the majority of sudden death early after acute MI, rather than primary arrhythmia. However, diagnosis of recurrent MI by autopsy is challenging and excludes electrocardiographic data to adjudicate arrhythmic causes. We examined the frequency of ischemia prior to treated ventricular tachycardia/fibrillation (VT/VF) and outcomes in patients using the wearable cardioverter defibrillator (WCD) following acute MI.
  
  
  OBJECTIVE
  Primary arrhythmia, rather than ischemia, is a frequent contributor to sudden death following MI.
  
  
  METHODS
  All patients treated for VT/VF over a 6-year period while wearing a WCD following acute MI with advanced left ventricular dysfunction (ejection fraction ≤35%) were included. Patients with ST-segment changes ≥0.1 mV before VT/VF were classified ischemic. Demographics and clinical outcomes were compared between those with ischemia-mediated vs primary arrhythmia.
  
  
  RESULTS
  Among 273 patients fulfilling study criteria, 15.4% had ischemia prior to VT/VF. Clinical and WCD use characteristics did not significantly differ between ischemic and primary VT/VF groups. Termination of VT/VF by WCD treatment approximated 96% in both groups. Survival 24 hours post-treatment was 88% and 84% (P = 0.54) for patients with and without ischemic VT/VF, respectively. Furthermore, 30-day cumulative survival for those with and without ischemic VT/VF was 77% and 70%, respectively (P = 0.57).
  
  
  CONCLUSIONS
  Ischemia is an infrequent cause of VT/VF following MI, contradicting previous study conclusions that recurrent MI is responsible for most post-MI sudden death. Etiology of VT/VF, however, did not influence defibrillation success or survival, which was high for both groups.
authors.affiliation: Interventional Cardiology Research, Piedmont Heart Institute, Atlanta, Georgia.
authors.forename: David E
authors.initials: DE
authors.lastname: Kandzari
authors.affiliation: Medical Affairs, ZOLL Medical Corporation, Pittsburgh, Pennsylvania.
authors.forename: Ramu
authors.initials: R
authors.lastname: Perumal
authors.affiliation: Heart and Vascular Center, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Deepak L
authors.initials: DL
authors.lastname: Bhatt
mesh_terms: D000368:Aged; D047548:Defibrillators; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications* / Q000175:diagnosis; D012189:Retrospective Studies; D012307:Risk Factors; D017180:Tachycardia, Ventricular / Q000453:epidemiology* / Q000209:etiology / Q000628:therapy; D014481:United States / Q000453:epidemiology