Severe PAH Recommendations for Severe PAH Referenced studies that support recommendations are summarized in Online Data Supplement 49. COR LOE Recommendations Diagnostic I B-NR Patients with ACHD with pulmonary vascular resistance 2.5 Wood units or greater ) should be assessed collaboratively by an ACHD cardiologist and an expert in pulmonary hypertension to develop a management plan.S4.4.6.1-1 S4.4.6.1-17 I B-NR Adults with septal or great artery shunts should undergo periodic screening for pulmonary hypertension with I B-NR Cardiac catheterization to assess pulmonary vascular hemodynamics is recommended for adults with septal or great artery shunts and clinical symptoms, signs, or echocardiographic findings suggestive of I B-NR In adults with septal or great artery shunts, cardiac catheterization with hemodynamics (performed before or at time of closure) is beneficial to assess suitability for CLINICAL STATEMENTS AND GUIDELINES Diagnostic (Continued) I C-EO BNP, chest x-ray, 6-minute walk test, and cardiac catheterization are useful for initial and follow-up evaluation of patients with ACHD with PAH. Synopsis Pulmonary hypertension is defined as elevation of mean pulmonary arterial pressure to 25 mm Hg at rest and does not imply a specific underlying pathophysiology. Pulmonary hypertension is further classified on the ba- sis of the presumed mechanism (including elevation of pulmonary venous pressure [denoted as postcapillary pulmonary hypertension ], parenchymal or restrictive lung disease, rheumatologic disease, portal hyperten- sion, toxin exposure, and thromboembolism). It is also classified by developmental or acquired anatomic ab- normalities of decreased pulmonary arterial capacitance, impedance, or stenosis throughout the pulmonary arte- rial vascular bed. PAH as initially described required pul- monary venous pressure 15 mm Hg with concomitant elevation of pulmonary vascular resistance. Although left-to-right shunting was the initial research model of triggered PAH, pulmonary hypertension in patients with ACHD can be caused by, or associated with, any of the factors described above. 