FIG 34.40 Resection of a supraannular fibrous ring Results The postoperative evolution following a mitral valve repair is more favorable than after a mitral valve replacement The early mortality rate is low: the largest and most recent series report an in-hospital mortality lower than 5%.20,21,32,34,35 Unlike the mitral valve replacement (see later), the risk of postoperative complete heart block is virtually nil after a mitral valve repair The long-term outcomes are globally excellent The 10-year survival rate is estimated at around 95% in most cohorts.20,34,35,89 At 10 years, the freedom from reoperation rate varies from 75% to 90%,32,34,90 and the freedom from valve replacement is around 85%.34,35 An age younger than 1 year at the time of repair and complex lesions such as the hammock valve and the parachute lesion have been identified as risk factors for reoperation and mortality.21,91,92 Mitral Valve Replacement As previously specified, one or several repairs must be attempted on the mitral valve before any replacement is performed The procedure should be postponed as much as possible if the mitral annulus is smaller than 18 mm (the smallest size for an intraannular insertion of a 15-mm mechanical valve) The usual indication is a persistent severe mitral stenosis with secondary pulmonary hypertension in a patient who has undergone multiple repairs Replacing a valve in a child exposes him or her to the risk of another replacement when the valve is outgrown The usual measures to prevent postoperative endocarditis on the prosthesis should be strictly enforced (see Chapter 56) Substitutes Mechanical Valves Mechanical prostheses are the only choice for mitral valve replacement in children Bioprostheses degenerate at a mid- or even short-term horizon in children and should not be implanted Mechanical valves require long-term anticoagulation with a target international normalized ratio of 3.0 (range, 2.5 to 3.5), as they are designed for a much larger flow than their actual functioning regimen in children Anticoagulation in children has considerably evolved and, with strict but standard surveillance protocols (self-testing at home), have very low complication rates.93 The smallest commercially available mechanical valve (Masters HP 15-mm prosthesis, Abbott Vascular) requires an 18- to 19-mm annulus to be fitted in intraannular position It was released in 2018 A few techniques have been suggested to overcome the incongruence between the mitral valve annulus and available prostheses in neonates and infants, such as the insertion of the prosthesis in supraannular position94,95 or the stretching or enlargement of the native mitral annulus.96 These devices are associated with very poor outcomes.33 Biologic Valves Mitral valve replacement with alternative bioprostheses made of bovine jugular veins have recently been described Further studies are needed to assess their durability, which will be limited These new techniques do allow for a bailout solution in patients with small mitral valve annuli The Melody stented valve (Medtronic) was designed as a right ventricle–to– pulmonary artery (RV-PA) conduit to be implanted percutaneously (see Chapter 18) The Boston group developed the use of the Melody valve for mitral valve replacement The stented valve is inserted surgically and can be further dilated percutaneously as the patient grows.97,98 Its transapical valve-in-valve implantation has also been reported.99 The Contegra valved conduit (Medtronic) was initially designed as an RV-PA conduit to be inserted surgically Our unit described its use for mitral valve replacement in an intraannular position by reversing the conduit for its insertion (Fig 34.41) The smallest available size is 12 mm; therefore it can be used in neonates It also allows for some growth of the annulus and the patient until a mechanical valve of adequate size can be inserted.100 FIG 34.41 Insertion of a Contegra valved conduit in mitral position Two commissures are sutured to the papillary muscles, and the third commissure is attached to the left ventricular posterior wall with artificial cords.100 Pulmonary Autograft: the Ross II Procedure This technique was described by Ross in 1967.101 It consists in replacing the mitral valve by the patient's own pulmonary valve (autograft) The pulmonary valve is replaced during the same procedure with a xenograft or pulmonary