Cur- rent evidence confirms that adults with repaired TOF are at risk of severe PR, RV dilation and dysfunction, LV dysfunction and electromechanical dyssynchrony, all of which contribute to adverse clinical outcomes late after TOF repair.S4.3.5-1,S4.3.5-20 S4.3.5-24 Despite intense in- terest and numerous publications on pulmonary valve replacement in adults with repaired TOF, optimal tim- ing for this intervention remains uncertain, and most studies have focused on preoperative RV volumes that would result in normalization of postoperative RV In adults with repaired Recommendations for TOF (Continued) COR LOE Recommendations CLINICAL STATEMENTS AND GUIDELINES TOF, prevalence rates for atrial and ventricular arrhyth- mias have been estimated to be 20% and 15%, respec- tively, with steep increases after 45 years of age.S4.3.5-28 The incidence of SCD after surgical repair of TOF is Currently, factors associated with SCD in patients with TOF have largely been identified from observa- tional, predominantly retrospective studies. Despite nu- merous studies that identified factors associated with malignant ventricular arrhythmias and SCD, risk stratifi- cation remains imperfect. Primary prevention ICDs should generally be consid- ered in patients who otherwise meet standard qualify- ing criteria (ie, LV ejection fraction 35% with NYHA class II or III symptoms).S4.3.5-31 S4.3.5-33 There may be a role for primary prevention ICDs in selected adults with TOF who have additional risk factors for SCD but would not meet standard criteria otherwise. See Section 3.3 for recommendations on who should perform surgeries, cardiac catheterization, and other procedures in these patients; Section 3.4 for rec- ommendations on diagnostic evaluation; Figure 4 for Figure 4. Pulmonary valve replacement in patients with TOF repair and PR. *Symptoms may include dyspnea, chest pain, and/or exercise intolerance referable to PR or otherwise unexplained. See recommendation 6 supporting text. 