Some can be ablated from the great cardiac vein or the epicardial surface, but others arise from an inaccessible region in close proximity to the left coronary artery precluding effective ablation.S8.1-14 Intramural sites of origin are infrequent but may require ablation on both the endocardial and epi- cardial surfaces of the LV ostium.S8.1-3 Complications from ablation of outflow tract VA are infrequent, but bleeding complications related to arterial and venous access, pericardial tamponade, and dam- age to the coronary arteries can occur. 2. In a prospective randomized comparison of anti- arrhythmic medications versus catheter ablation, metoprolol or propafenone was shown to have modest effectiveness when used to suppress RVOT PVCs, though with a far higher rate of recurrence than catheter ablation.S8.1-4 Non-dihydropyradine calcium channel blockers suppress arrhythmia in 8.2. Papillary Muscle VA Recommendation for Papillary Muscle VA (PVCs and VT) References that support the recommendation are summarized in Online Data Supplement 47. COR LOE Recommendation I B-NR In patients with symptomatic VA arising from the papillary muscles for whom antiarrhythmic medications are ineffective, not tolerated, or not the patient s preference, catheter ablation is useful.S8.2-1 S8.2-5 Recommendation-Specific Supportive Text 1. The papillary muscles of the LV or RV can be the site of origin of VA in the presence or absence of struc- tural heart disease.S8.2-1 S8.2-5 Idiopathic left and right ventricular papillary muscle VA are most commonly PVCs and NSVT, and are usually exercise-related and may be induced by intravenous epinephrine or These arrhythmias have a focal, nonreentrant mechanism. 