Material and Method: Retrospective design was used. Patients (n = 115) from Siriraj Hospitals with ischemic or non-ischemic cardiomyopathy who underwent ICD implantation for primary prevention were studied. Clinical data and ICD therapy data were obtained from medical records and ICD interrogation reports.

Results: First appropriate ICD therapy for ventricular tachycardia (VT) or ventricular fibrillation (VF) were seen in 22 patients (19%) of whom 11 (9.5%) received ICD shock and 11 patients (9.5%) received anti-tachycardic pacing. Lack of beta-blocker use and lack of aldosterone antagonist use were identified as significant predictors of appropriate therapy. There was no difference in prevalence of appropriate ICD therapy between ischemic and non-ischemic groups. The freedom from first appropriate therapy at 1, 2 and 3 years was 88%, 80% and 78%. The freedom rate was constant after the third year

Conclusion: Nearly one-fifth of chronic LV dysfunction patients with primary prevention ICD implantation experience appropriate ICD therapy. Most first appropriate ICD therapy occurs within 2 years after implantation. Lack of beta-blocker use and lack of aldosterone antagonist use were significant predictors of appropriate therapy.

Keywords: Implantable cardioverter defibrillator, Sudden cardiac death, Primary prevention, Predictors