In NICM, the reentrant circuits are more variable in loca- tion, often involve the epicardial surface of either ven- tricle and frequently extending into the midmyocar- dium where ablation may be difficult to achieve from either surface. In tetralogy of Fallot specific reentry paths have been defined.S5.4.3-1 Electroanatomical map- ping that helps clarify the relation of electrophysiologi- cal abnormalities to cardiac anatomy is commonly em- ployed. Areas of scar can be appreciated as regions of relatively low electrogram voltage. For scar-related VTs, hemodynamic intolerance often limits mapping during VT. Ablation is then often guided by substrate mapping, in which areas of scar and potential reentry circuit sub- strate are delineated in electroanatomic maps based on electrocardiographic and pacing characteristics as- sessed during hemodynamically stable sinus or paced rhythm. Catheter ablation of scar-related VT requires an advanced level of experience by the operator, electro- physiological laboratory staff, and anesthesiologists as well as availability of surgical back-up and specialized mapping, imaging, and ablation equipment.S5.4.3-2,S5.4.3-3 5.5. Surgery and Revascularization Procedures in Patients With Ischemic Heart Disease Recommendations for Surgery and Revascularization Procedures in Patients With Ischemic Heart Disease References that support the recommendations are summarized in Online Data Supplement 11. COR LOE Recommendations I B-NR Patients with sustained VA and survivors of SCA should be evaluated for ischemic heart disease, and should be revascularized as I C-EO In patients with anomalous origin of a coronary artery suspected to be the cause of SCA, repair or revascularization is recommended. Recommendation-Specific Supportive Text 1. Myocardial ischemia is a cause of sustained poly- morphic VT/VF, and revascularization is an effec- tive treatment to prevent myocardial ischemia. 