Aim: To analyse the characteristics and outcome of patients with idiopathic dilated cardiomyopathy (DC) considered at high risk of sudden death (SD) and treated with implantable cardioverter defibrillators (ICD) for primary prevention (Group A) in comparison with patients treated with ICDs because of previous sustained ventricular tachyarrhythmias or syncope (Group B).

Methods: Group A consisted of 27 patients with at least two of the following criteria: left ventricular end-diastolic diameter (LVEDD) > or =70 mm (74%), LV ejection fraction (LVEF) < or =30% (78%), non-sustained ventricular tachycardia (VT) (56%), long history of disease (> or =48 months since diagnosis, 85%) and family history of SD (11%). Group B consisted of 27 patients treated with ICDs because of sustained VT/fibrillation (n=18) or syncope (n=9).

Results: NYHA class, LVEF, LVEDD and amiodarone treatment were similar in the two groups. Patients in group A were younger (46+/-15 vs 59+/-17 years, P=0.0008), were more often treated with beta-blockers (89% vs 62%; P=0.02) and had a longer interval since diagnosis (86+/-60 vs 40+/-50 months; P=0.004). Twelve month rates of appropriate intervention (AI) were 41% in Group A and 57% in group B (P NS). In group A, after a mean follow-up of 21+/-14 months, patients showing the combination of LVEF < or =30% and LVEDD > or =70 mm had the highest frequency of AI (76% vs 10%, P=0.005). In group B, after a mean follow-up of 33+/-23 months, 78% of patients with syncope had AI. Total and sudden deaths were 11% and 4% in group A and 19% and 4% in group B (P NS).

Conclusions: Patients with idiopathic DC treated with ICD for primary prevention because they were considered at high risk of SD according to clinical criteria showed a high rate of AI, similar to that of patients treated for secondary prevention. The highest rate of AI was seen in patients with both severe dysfunction and dilatation and in those with previous syncope.