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Background -Right ventricular outflow tract obstruction(RVOTO) is a common problem after repair of congenital heart disease. Percutaneous pulmonary valve implantation(PPVI) can treat this condition without consequent pulmonary regurgitation or cardiopulmonary bypass. Our aim was to investigate the clinical and physiological response to relieving RVOTO. Methods and Results -We studied 18 patients who underwent PPVI for RVOTO(72%male, median age 20 years) from a total of 93 who had this procedure for various indications. All had a right ventricular outflow tract(RVOT)gradient >50 mm Hg on echocardiography without important pulmonary regurgitation(less than mild or regurgitant fraction< 10%on magnetic resonance imaging[MRI]). Cardiopulmonary exercise testing, tissue Doppler echocardiography, and MRI were performed before and within 50 days of PPVI. PPVI reduced RVOT gradient(51.4 to 21.7 mm Hg, P< 0.001)and right ventricular systolic pressure(72.8 to 47.3 mm Hg, P< 0.001) at catheterization. Symptoms and aerobic(25.7 to 28.9 mL·kg-1.min-1, P=0.002) and anaerobic(14.4 to 16.2 mL·kg-1.min-1, P=0.002) exercise capacity improved. Myocardial systolic velocity improved acutely(tricuspid 4.8 to 5.3 cm/s, P=0.05; mitral 4.7 to 5.5 cm/s, P=0.01), whereas isovolumic acceleration was unchanged. The tricuspid annular velocity was not maintained on intermediate follow-up. Right ventricular end-diastolic volume(99.9 to 89.7 mL/m2, P< 0.001) fell, whereas effective stroke volume(43.7 to 48.3mL/m2, P=0.06) and ejection fraction(48.0%to 56.8%, P=0.01) increased. Left ventricular end-diastolic volume(72.5 to 77.4 mL/m2, P=0.145), stroke volume(45.3 to 50.6 mL/m2, P=0.02), and ejection fraction(62.6%to 65.8%, P=0.03) increased. Conclusions -PPVI relieves RVOTO, which leads to an early improvement in biventricular performance. Furthermore, it reduces symptoms and improves exercise tolerance. These findings have important implications for the management of this increasingly common condition.