CLINICAL STATEMENTS AND GUIDELINES 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; Table 29 for routine testing and follow-up intervals; and Online Data Supplement 25 for referenced studies. Recommendation-Specific Supportive Text 1. There is a progressive loss of sinus rhythm in patients who have undergone the Senning or Mustard procedure for d-TGA, and the develop- ment of significant sinus bradycardia, while often asymptomatic, is important to identify, because it will influence and limit treatment with antiar- rhythmic medications. 2. Patients with d-TGA with atrial switch have ab- normal cardiac anatomy, with common long-term complications including systemic RV dysfunc- tion, TR, subpulmonic obstruction, obstruction of systemic or pulmonary venous return, and baffle leaks. Imaging should be goal-directed with an understanding of potential long-term sequelae, and nuanced for the patient s particular CMR offers quantification of systemic RV function and should be used rou- tinely unless there are contraindications. Late gad- olinium enhancement is an important tool that can identify areas of myocardial scar that are associ- ated with adverse clinical markers including atrial The importance of change in late gadolinium enhancement over time in direct- ing care is less clear, so repetitive use of gadolinium contrast for this purpose is of less value. 3. Recognizing both the abnormal venous path- ways after atrial switch palliation and the risk of thromboembolic complications from transvenous pacing leads in those with intracardiac shunts, thorough assessment of the venous pathways for either obstruction or baffle leak is a prudent step before lead placement or revision. Baffle leaks should be sought because they are common and may alter treatment considerations such as thromboembolic concerns or options for closure. 