A minority of conduits may show early dysfunction because of kinking or aneurysmal di- lation. The remainder will become dysfunctional over time and usually require replacement or intervention because of progressive stenosis within the conduit or at the valve, and/or valvular regurgitation, at a mean inter- val of 10 to 15 years from placement, although some conduits may last much longer than that.S4.3.6-15,S4.3.6-16 See Section 3.3 for recommendations on who should perform surgeries, cardiac catheterization, and other procedures in these patients; Section 3.4 for rec- ommendations on diagnostic evaluation; and Table 28 for routine testing and follow-up intervals. Recommendation-Specific Supportive Text 1. Coronary compression testing generally involves simultaneous selective coronary angiography or aortography and balloon dilation in the RVOT, to ascertain whether a balloon expanded stent will compress the coronary artery. Coronary artery compression with conduit balloon angioplasty or stenting occurs in approximately 5% to 6% of patients with right ventricle to-PA conduits and usually involves the left main/left anterior descending in those with conventional coronary anatomy. Patients with anomalous right or left coronary arteries are at risk of coronary com- pression as are those with reimplanted coronary arteries. 2. Right ventricle to-PA conduit stent fracture is common and occurred in approximately 26% of patients in the Melody Valve Investigational Device Exemption trial,S4.3.6-7 especially in patients who did not undergo conduit prestenting. Stent fracture typically presents with progressive ste- nosis and in those with transcatheter valves may also present with worsening PR. Patients with an increase in PR or PS should have fluoroscopic or x-ray assessment to rule out stent fracture. 