The results of this study showed that surgical management of congenital mitral valve regurgitation according to Carpentier’s classification produces good mid- and long-term outcomes.
In our study, the mortality rate was 0%, the overall 5-year rate of freedom from mitral valve replacement was 92%, and the 5-year rate of freedom from reoperation was 67 − 80% among the four Carpentier’s types. Chauvaud et al. reported a 10-year mortality rate of 88% and a rate of freedom from reoperation of 68% . This demonstrates that the mid-term outcomes of children who underwent mitral valve repair at our institution are acceptable.
In patients with Carpentier’s type 1 mitral valve malformation, the lesions were localized and surgical outcomes were satisfactory when using Kay − Reed’s annuloplasty for annular dilation, and cleft suture for cleft leaflet. Previous studies have reported similar results [4, 12, 13]. However, in patients with a large cleft reaching the annular ring (such as our Case 2), performing only cleft suture could influence the valve leaflet dimensions and worsen the mitral regurgitation. Therefore, patch augmentation seems to be a better choice for these patients .
For Carpentier’s type 2 mitral valve malformation, previous studies have reported that artificial chordae placement is an effective treatment [15–17]. However, Minami et al. reported a 5-year rate of freedom from reoperation of 89% and emphasized that it is difficult to decide on the size of the artificial chordae, due to considerations concerning the patients’ growth . For the same reason, we opted for Kay − Reed’s annuloplasty as the initial treatment in these patients. If the mitral regurgitation could not be controlled, artificial chordae placement was also performed, particularly in cases of leaflet prolapse caused by a defect of the strut chordae, such as in Case 3.
For Carpentier’s type 3 mitral valve malformation, we initially performed Kay − Reed’s annuloplasty, which was then supplemented by edge-to-edge paracommisural repair in cases of insufficient mitral regurgitation control, such as Cases 4 and 5 .
In cases of Carpentier’s type 4 mitral valve malformation, Chauvaud et al. reported that mitral valve repair is extremely difficult and surgical outcomes tend to be unsatisfactory . Type 4 lesions are usually not isolated and are often characterized by a constellation of other pathological changes of the mitral valve leaflets, annulus, and ring. Therefore, the majority of patients require one or more surgical techniques. Among the techniques performed in these patients at our institution, cusp elongation seemed to be the most effective. However, this technique has been reported to have some limitations. Namely, in some cases, papillary muscle splitting is required in addition to cusp elongation, and good effects can only be obtained with sufficient mitral valve diameter . In cases where cusp elongation was ineffective, we had no choice other than mitral valve replacement. This is because we generally opted for minimally invasive methods, such as edge-to-edge repair and Kay − Reed’s annuloplasty, and if these were found to be insufficient to control the mitral regurgitation, we performed cusp elongation. In Case 6, at primary repair, we evaluated the mechanism of mitral regurgitation as idiopathic rupture of the chordae tendineae and performed artificial chordae placement. However, the true mechanism underlying mitral regurgitation was a hammock mitral valve, which was only perceived at the time of reoperation. This case highlights the importance of accurate assessment of the pathophysiology of mitral regurgitation based on preoperative echocardiography and intraoperative findings.
The study had some limitations. First, this was a single-center, retrospective study that only included a small number of patients. Second, the effect of improvements in surgical technique with increasing surgical experience was not measured.
In conclusion, surgical management of congenital mitral valve regurgitation according to Carpentier’s classification provided good mid- and long-term outcomes in our patients, with a surgical mortality rate of 0% and a 5-year rate of freedom from mitral valve replacement of 92%. The surgical outcomes of Carpentier’s type 1, 2, and 3 mitral lesions were good, while the more complicated type 4 lesions required a combination of surgical techniques, including annuloplasty, artificial chordae placement, edge-to-edge repair, and cusp elongation.