Surgical valvotomy is usually sufficient, particularly when the pulmonary annulus is not hypoplastic. Pulmonary valve replacement may be necessary Table 22. Severity of RVOT Obstruction Mild Peak gradient <36 mm Hg (peak velocity <3 m/s) Moderate Peak gradient 36 64 mm Hg (peak velocity 3 4 m/s) Severe Peak gradient 64 mm Hg (peak velocity >4 m/s); mean gradient >35 mm Hg Estimations of RV systolic pressure by TR velocity is part of the echocardiographic assessment of RV obstruction, as Doppler measurements across the RV obstruction itself may be unreliable. RV indicates right ventricular; RVOT, right ventricular outflow tract; and TR, tricuspid regurgitation. CLINICAL STATEMENTS AND GUIDELINES Table 23. Valvular PS: Routine Follow-Up and Testing Intervals Frequency of Routine Follow-Up and Testing Physiological Stage A* (mo) Physiological Stage B* (mo) Physiological Stage C* (mo) Physiological Stage D* (mo) *See Tables 3 and 4 for details on the ACHD AP classification system. 6-minute walk test or CPET, depending on clinical indication. ACHD indicates adult congenital heart disease; CPET, cardiopulmonary exercise test; ECG, electrocardiogram; PS, pulmonary stenosis; and TTE, transthoracic echocardiogram. Figure 3. Isolated PR after repair of PS. *Significant PR causes RV dilation. If a patient has moderate or greater PR and normal RV size, most likely the estimation of PR severity is inaccurate or there may be restrictive RV physiology, which would warrant further investigation. Symptoms may include dyspnea, chest pain, and/or exercise intolerance referable to PR or otherwise unexplained. ACHD indicates adult congenital heart disease; CPET, cardiopulmonary exercise test; PR, pulmonary regurgitation; PS, pulmonary stenosis; and RV, right ventricular. CLINICAL STATEMENTS AND GUIDELINES when there is marked dysplasia of the pulmonary valve or significant hypoplasia of the annulus. 3. 