RV ischemia and infarction occur, with perfusion defects identi- fied by myocardial perfusion studies in >40% of patients in this population.S10.8-49,S10.8-50 Risk factors for cardiac arrest in patients with transposition and atrial baffle repairs include prior ventricu- lar septal defect closure, symptoms of HF, atrial arrhythmia, RVEF <30% to 35%, and QRS dura- In the single multicenter study assessing outcomes after implantation of an ICD in patients with prior atrial baffle repair of transposition of the great arteries, the lack of beta blockers was associated with a high risk of appro- priate ICD therapy.S10.8-26 Atrial arrhythmias fre- quently precede VT in transposition patients, and treatments for atrial tachycardia including cath- eter ablation, antitachycardia pacing algorithms, and beta blockers are important to reduce ICD 9. The risk of SCD is increased among patients with adult congenital heart disease compared with the general population, with the median age at death ranging from 30 to 49 years of The risk of SCD is highest among patients with moderate or severe complexity congenital heart disease, and accounts for approximately 25% of cardiac causes Patients with septal defects and a positive fam- ily history of septal defects, cardiomyopathy, or bundle-branch block/conduction defects may have the gene mutation NKX2.5, which portends an increased risk of early SCD; genetic testing and early consideration of ICD implantation if positive Patients with repaired complex forms of congenital heart disease have undergone multiple intracardiac surgeries in the first few decades of life with resultant hypertro- phy and risk for subendocardial ischemia as well as scar formation contributing to VT/VF. 