Open-label single-center registries and cohort studies of adults with Eisenmenger syndrome, attributable to shunts other than ASD/VSD or with complex congenital heart lesions, suggest benefit in functional capacity or hemodynamics after months of endothelin receptor antagonist Patients with ACHD and Down syndrome have greater likelihood to de- velop pulmonary hypertension, and they have unique comorbidities that influence the nature of their pulmonary hypertension, the metrics used in follow-up, and the potential for benefit from as well as adverse response to therapy. Open-label single-center registries and cohorts of adults with Down syndrome and Eisenmenger syndrome suggest benefit in subjective and/or objective functional capacity after months of endothelin re- ceptor antagonist therapy, generally as contrasted to performance before institution of endothe- lin receptor antagonist therapy.S4.4.6.2-8 S4.4.6.2-10 Accurate diagnosis of PAH and Eisenmenger syn- drome remains essential before initiating such therapy. CLINICAL STATEMENTS AND GUIDELINES regarding PDE-5 inhibitor therapy for adults with Eisenmenger syndrome have limita- tions, but are supported by multiple open-label prospective studies and information from a large single-center retrospective registry.S4.4.6.2-1,S4.4.6.2-11 These studies suggest benefit in functional capacity and hemodynamics after use of either sildenafil or tadalafil at varying doses and for varying periods of follow-up. Benefit was ei- ther in comparison to subjects performance before institution of therapy or to other adults with similar Eisenmenger syndrome anatomy and physiology who were not prescribed PDE-5 inhibitors. 4.4.7. Coronary Anomalies Coronary abnormalities are among the most com- mon congenital cardiovascular anomalies, surpassing in prevalence nearly all others combined. Coronary anomalies include anomalous aortic origin of a coro- nary artery (AAOCA), coronary fistula, and myocardial bridge. Many congenital coronary abnormalities have a benign outcome. 