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. Any of the 3 RV papillary muscles may be the site of origin and catheter ablation is usually effective.S8.2-2 In 1 study, successful ablation was achieved in all 8 patients with a reduction in PVC burden from 17 20% to In the left ventricle, the site of origin may be either the posteromedial or the anterolat- eral papillary muscles.S8.2-1,S8.2-4,S8.2-5 Multiple VA QRS morphologies were observed in 47% of patients, and ablation on both sides of the papillary muscle is required in some patients.S8.2-4 Achieving adequate catheter stability can be challenging. Acute abla- tion success is high, but recurrences are more fre- quent than for idiopathic outflow tract VA. Serious complications, including valve injury, appear to be infrequent. The risks of catheter ablation include bleeding related to arterial and venous access and a low risk of pericardial tamponade. 8.3. Interfascicular Reentrant VT (Belhassen Tachycardia) Recommendations for Interfascicular Reentrant VT (Belhassen Tachycardia) References that support the recommendations are summarized in Online Data Supplement 48. COR LOE Recommendations I B-NR In patients with verapamil-sensitive, idiopathic LVT related to interfascicular reentry for whom antiarrhythmic medications are ineffective, not tolerated, or not the patient s preference, catheter ablation is I B-NR In patients with sustained hemodynamically tolerated verapamil-sensitive, idiopathic LVT related to interfascicular reentry, intravenous verapamil is recommended for IIa C-LD In patients with recurrent verapamil-sensitive idiopathic LVT, chronic therapy with oral verapamil can be useful.S8.3-7 S8.3-10 Recommendation-Specific Supportive Text 1. 