Discussion

Congenital malformations of the mitral valve were identified in approximately 0.5% of the 13,400 subjects in an echocardiographic study. ^{Reference Moore, Adatia and Spevak1,Reference Maskatia2} Isolated congenital mitral stenosis is a quite rare entity. Congenital mitral stenosis is usually associated with other cardiac anomalies such as Shone’s complex, subvalvular aortic stenosis, and aortic coarctation. ^{Reference Remenyi and Gentles3,Reference Séguéla, Houyel and Acar4} Typical congenital mitral stenosis is characterised by thickened and folded leaflets, chordae tendineae that are shortened and lacking interchordal spaces, and papillary muscles that are underdeveloped and closely spaced. Thus, basic classifications like subvalvar, valvar, or supravalvar stenosis represent more benchmarks along a continuous spectrum as opposed to completely separated groups. The preoperative evaluation of the anatomical substrate is crucial for the successful management of congenital mitral stenosis. Echocardiographic studies of congenital mitral valve disorders are now typically performed level by level. Thus, the mitral valve, including the valvar leaflets, tensor apparatus, and papillary muscles, should be evaluated as an entire complex. ^{Reference Moore, Adatia and Spevak1–Reference Banerjee, Kohl and Silverman5} This approach leads to a final diagnosis from the morphologic and physiologic perspectives. Varying effects of these lesions may be observed on valve function. The severity of the disease is influenced by various factors, including the degree of obstruction, the presence of regurgitation, the existence and severity of associated pulmonary hypertension, and the existence of associated heart and non-cardiac malformations. When indicated, surgical repair provides good long-term results.

Kabuki syndrome is a genetically heterogeneous disorder distinguished by skeletal anomalies, congenital heart defects, developmental delay, anorectal anomalies, persistence of fetal fingertip pads, developmental delay, growth defect with feeding difficulties, anorectal anomalies, renal malformations, anorectal anomalies, and the presence of distinct facial features such as sparse eyebrows and long palpebral fissures, large everted ears, eversion of the lateral third of the lower eyelids, and a pillowed lower lip. ^{Reference Digilio, Gnazzo and Lepri6} CHDs are quite common in Kabuki syndrome with almost all being left-sided cardiac anomalies like aortic coarctation, hypoplastic left heart syndrome, Shone syndrome, aortic valve stenosis, and mitral valve stenosis. Isolated congenital mitral stenosis in Kabuki syndrome is also rare, with being reported only in two cases before. ^{Reference Digilio, Gnazzo and Lepri6,Reference Yoon, Ahn and Kwon7}

In our patient when the mitral valve was examined intraoperatively, it was found to be not appropriate for satisfactory repair as the valve was showing severe stenotic features in multilevel fashion. First, the annulus was hypoplastic with no supravalvar involvement. Secondly, both leaflets were severely dysplastic, thickened, and rolled. Valvar orifice was so small even 4 mm dilator was barely passing through. Third, there were two asymmetric papillary muscles, one being severely hypoplastic, and they were closely spaced. The dominant one was elongated, displaced toward the annulus, connected to the free edge of the mitral leaflet by a bridge of fibrous tissue, and highly positioned within the left ventricle. It had a wide base and was attached to the lateral side of the left ventricle. Subvalvar area was crowded with chordae tendinae were shortened and thickened with the absence of interchordal spaces and predominantly connected to the dominant papillary muscle.

With these morphologic features, we opted for valve replacement as repair was not feasible. The surgical outcomes for congenital mitral stenosis exhibit considerable variability, with a strong dependence on factors such as the experience of the institution, the age and weight of the patient, the extent of annular hypoplasia, the presence of associated left-sided obstructive lesions, and the severity of pulmonary hypertension. In paediatric patients, the preference lies with valve repair over valve replacement. Mitral valve replacement is associated with significant risk, as evidenced by operative mortality rates ranging from 0 to 36%, despite the notable progress made in surgical methods and the availability of several valve options. However, when repair is not anatomically feasible, valve replacement is performed as the last recourse due to the fact that suboptimal primary repair is a significant predictor of reoperation and further morbidity and mortality risks. ^{Reference Henaine, Roubertie, Vergnat and Ninet8,Reference Alghamdi, Yadava and Van Arsdell9}

Several techniques are described for mitral valve replacement in small children with small annulus. Unlike aortic valve replacement, options for annular enlargement are limited. Subaortic obstruction may result from an attempt to enlarge the prosthesis during MVR; this course of action should be avoided. Supra-annular replacement of the valve in children with a small annulus has favourable operative survival and low heart block rate. ^{Reference Henaine, Roubertie, Vergnat and Ninet8–Reference Overman, Moga, Stephens, Dearani and MacIver10} Considering the small annulus of our patient, we also decided to implant the mechanical valve in supra-annular fashion. Post-operative course was uneventful without any rhythm problems and he has been doing well clinically during the 10-months follow-up with regular INR checks.

Although it is widely recognised that syndromic patients often have a poorer prognosis compared to those without syndromes, we maintain the belief that attaining a competent valve with replacement would be beneficial in long-term without any additional procedures while being closely monitored.