Currently, MVP is the first choice of treatment for severe mitral insufficiency caused by PMPL. CR and QR procedures have been proven to have good short- and long-term outcomes17,18.
Postoperative hemolysis is a serious complication of MVP and is dangerous and even life-threatening. It usually occurs during the early stages of MVP19, 20. In this study, we found that in the early stages, the incidence of postoperative hemolysis was significantly higher in the QR group than in the CR group. An important finding of our study was that the median interval between MVP and hemolysis was very short. Therefore, it is reasonable to assume that hemolysis after MVP is surgery related. We found that all patients with postoperative hemolysis had a small eccentric regurgitant blood flow with high shear stress. We analyzed intraoperative TEE to identify patients at risk of such a complication; however, we encountered difficulties in conducting further analysis and research due to the small number of positive cases.
According to our analysis, the cause of postoperative hemolysis is related to the MVP technology. In the QR group, the cutting and sewing technique, with the two cutting margins sutured together after QR of the mitral leaf tissue. When the suture was not tight, or the suture tension was too high, the suture margins were torn, and small gaps occurred, resulting in small eccentric regurgitant blood flow with high shear stress, leading to hemolysis21, 22. Alternatively, there may be small protrusions in the suture margin when the posterior leaf is resected and resutured, which may not fit the anterior valve well when the valve is closed, or there may be small folds after the anastomosis, leading to a small eccentric regurgitant blood flow with high shear stress, leading to hemolysis. However, in the CR group, the procedure did not destroy the original structure of the leaflets, and it was difficult to produce small gaps and eccentric regurgitant blood flow. The fractured original chordae tendineae were replanted and restored to their original physiological state, and the anterior and posterior leaflets were completely combined. Therefore, hemolysis can be avoided to an extent, and when small regurgitation of blood flow appears, they also present with central regurgitation. Therefore, more attention should be paid to the direction and source of regurgitation for some small regurgitation blood flow in the TEE examination before the end of surgery.
Left ventricular enlargement is a common cause of MR, and its pathogenesis is complex. Mitral valve regurgitation increases the volume load of the left ventricle, leading to left ventricular remodeling and resulting in downward and apex displacement of the papillary muscle. Increased mitral valve traction can lead to increased left ventricular papillary muscle tone, lengthening, or even rupture of chordae tendineae, causing acute or chronic heart failure. In addition, myocardial contractility was weakened, and left ventricular dilation and mitral valve annular dilation were observed. This eventually leads to incomplete valve closure and MR23–25. In this study, we found that the left ventricular diameter decreased to varying degrees in all patients after MVP, and the reduction was greater in the CR group. During the CR procedure, artificial chordae tendineae were used to retract the prolapsed leaflets and fixed on the original left ventricular papillary muscles, which maintained the original left ventricular function to the maximum extent, preserved the subvalvular structure, and maintained the continuity of the mitral valve device. This played an important role in maintaining the left ventricular function26. In addition, the artificial chordae tendineae has a traction effect on the papillary muscles; therefore, it has a certain effect on preventing left ventricular dilatation27. Even when recurrent MR occurs at later follow-up, the rate of left ventricular remodeling is limited, preventing left ventricular enlargement within a short period.
The key to the CR procedure is determining the length of the artificial chordae tendineae. Too long or too short chordae tendineae will cause incomplete valve closure and MR28, 29. Our experience was based on the length of the chordae tendineae and the anterior and posterior mitral leaflet closure lines. If necessary, methylene blue was used to identify the height and surface of the anterior and posterior mitral leaflets. After adjusting the length of the artificial chordae tendineae, they were temporarily fixed with titanium clips. A water injection test was performed to observe the closure of the mitral leaflets.
The QR procedure can also reduce MR and left ventricular afterload, such that the left ventricle diameter can be reduced, which will reduce the area of the posterior mitral leaflet tissue, resulting in the reduction of the height and area of anterior and posterior mitral leaflets. Our experience in processing was carefully comparing and measuring the leaflet with an appropriate excision area. The width of the posterior mitral leaflet is generally 10–20 mm. To ensure good valve competency, the heights of the anterior and posterior mitral leaflets should be kept as good as possible (> 12 mm). Finally, both methods use a mitral valvuloplasty ring to restore the normal size and shape of the annulus, prevent further expansion of the mitral annulus, increase the junction surface of the anterior and posterior mitral leaflets, and increase the durability of the mitral valve30. However, in some patients with chronic left ventricular enlargement, the myocardium of the left ventricle undergoes remodeling, leading to failure of the left ventricle to recover its original physiological state. Another problem is that there may be too much resection area in the QR procedure, which may lead to anterior movement of the valvular anastomosis line and systolic anterior motion, leading to left ventricular outflow tract obstruction31. Although this phenomenon was not observed in this study, its occurrence must always be carefully avoided.
Based on our previous analysis, QR techniques reduced the junction surface of the anterior and posterior mitral leaflets; therefore, they were also tested for valve durability, which was also confirmed in our study. Although the incidence of reoperation for recurrent MR was similar between the two groups, the interval between the first operation and reoperation was shorter in the QR group than in the CR group. For MR, the surface of the anterior and posterior mitral leaflets junction is the key factor, and recurrent MR after MVP is mostly caused by the lack of the anterior and posterior mitral leaflets junction. In patients with acute chordae tendineae rupture, the QR method may result in insufficient posterior mitral leaflet area, poor mitral anterior and posterior mitral leaflets fit, or very high tension of the suture line at the edge of the posterior mitral valve. However, artificial chordae tendineae can avoid this defect32. Although the QR techniques had good height and area of the anterior and posterior mitral leaflets junction, the surgical effect was satisfactory. In the long-term follow-up, the left ventricular diameter expanded again, causing a decline in the height and area of the anterior and posterior mitral leaflets junction, resulting in a gradual increase in recurrent MR, which in turn affected the further expansion of the left ventricle diameter. This was also confirmed by the results of LVEDD in both groups during the long-term follow-up in our study.
Limitations
This was a single-center, retrospective study with a small number of patients. Therefore, a multicenter study with larger sample size is needed. Only patients with posterior mitral valve prolapse were included in this study. However, many patients with anterior mitral valve prolapse or bilateral mitral valve prolapse are also involved in practical applications, which require further controlled studies. Simultaneously, our hospital uses not only CR and QR procedures but other techniques such as edge-to-edge, chordae tendineae transfer, and valve leaflet folding. However, these procedures were not included in this study because of the small number of cases, which may have biased the results.