The subcuta- neous ICD may not be a good therapy for these patients due to the higher risk of T-wave over- sensing seenin this population; however, data are 3. Idiopathic VF may be initiated by PVCs that arise from the outflow tracts or the His-Purkinje system within either the right ventricle or left Some patients have clusters of VF episodes (electrical storm) that typi- cally present as PVCs initiating polymorphic VT/VF. The PVCs usually have a consistent QRS morphol- ogy and a short coupling interval and can be tar- geted for ablation to control the arrhythmia.S8.4-11 For PVCs from the Purkinje system, the ablation target is a high-frequency Purkinje potential pre- ceding the PVCs. When episodes are induced by short-coupled PVCs arising from the outflow tracts, the ablation target is the site of earliest ventricular activation. Patients with idiopathic VF often have periods of frequent VT/VF interspersed with peri- ods of relative quiescence.S8.4-11,S8.4-14 To maximize the probability of successful ablation, the proce- dure is best performed during periods of frequent PVCs. Less-frequent episodes of VF may be ame- nable to ablation if frequent PVCs with a consis- tent QRS morphology are present. When the PVCs can be identified, ablation is highly successful, but late recurrences are observed in approximately 10% of patients such that implantation of an ICD is prudent even if ablation is acutely successful. The risks of catheter ablation include bleeding at the site of arterial or venous access and a small risk of pericardial tamponade. Therapy with quinidine acutely and chronically can suppress recurrent VF episodes in some patients.S8.4-22 9. PVC-INDUCED CARDIOMYOPATHY Recommendations for PVC-Induced Cardiomyopathy References that support the recommendations are summarized in Online Data Supplement 50. 