Does an aortopulmonary shunt before repair of tetralogy of Fallot limit exercise tolerance in long-term survivors?

The purpose of this study was to evaluate the impact of an aortopulmonary shunt on exercise capacity in long-term survivors after total repair of tetralogy of Fallot (17.6(2.0) years' follow-up). Submaximal exercise tests, pulmonary function tests, lund diffusion tests for carbon monoxide, two-dimensional and Doppler echocardiography were performed in 12 patients with an aortopulmonary shunt (group A) and in 21 patients (group B) without a shunt before repair. There were no significant differences in two-dimensional and Doppler echocardiographic findings nor in pulmonary function. Group A showed a significantly lower diffusion capacity of the lung for carbon monoxide at rest (66.2(13.0)% versus 84.1(9.5)%; P < 0.01) and at the anaerobic threshold (71.8(11.0)% versus 87.2(9.8)%; P < 0.01) as well as a significantly reduced physical working capacity at ventilatory anaerobic threshold (1.6)(0.32) W/kg versus 2.41(0.43) W/kg; P < 0.01). A negative correlation was observed between the duration of palliative shunts and diffusion capacity of the lung for carbon monoxide at rest at ventilatory anaerobic threshold (r = -0.8635 and -0.9108 respectively). A shunt placed before definitive repair impairs the long-term working capacity, probably by diminishing the diffusion capacity of the lung for carbon monoxide, especially if the shunt is in place for more than 20 months.