Discussion
In the present study, a TV with two posterior leaflets was an independent predictor of additional procedures. The TV consists of multiple posterior leaflets in about half of patients, and the morphological diversity of these leaflets has attracted attention among researchers (10,17,18).
We consider that postoperative TR can be divided into two types: TR observed immediately after surgery (residual TR) and TR that worsens during follow-up despite the fact that it was controlled immediately after surgery (recurrent TR). Fukuda et al. (9) reported that residual TR soon after the operation causes volume overloading of the right ventricle and further right ventricular dilatation and dysfunction, resulting in worsening TR. Therefore, we consider that controlling the residual TR grade during the perioperative period is crucial to avoid the development of later TR.
Upon completion of the ring annuloplasty, we routinely checked TV by the saline test. If residual TR was found, we performed additional edge-to-edge repair at the sites of the leakage. Although we could control TR with ring annuloplasty alone in most patients, additional sutures were necessary to control residual TR in some patients. The locations and numbers of edge-to-edge repairs varied among the patients according to the features of the residual TR. Thus, we investigated the crucial causes of complicated TV repair in our study.
The surgical technique to control TR depends upon the mechanism of TR, such as annular dilatation, prolapse or tethering of the leaflets, or right ventricular dilatation. We suspected that morphological differences of the TV may make it difficult to control TR during surgery. Therefore, we focused on TV morphology and the complexity, to control TR. We set the endpoint as whether additional procedures were needed during the operation. According to the univariate and multivariate logistic regression analyses, patients with two posterior valve leaflets required additional procedures for reduction of TR. Moreover, patients with two posterior valve leaflets had higher TR score before operation and one year after operation than those with one posterior valve leaflet. There was no difference in the size of the TV regardless of the number of posterior leaflets. Considering these results, we concluded that the presence of two posterior valve leaflets itself has the potential to increase regurgitation, resulting in the need for complex procedures in TV repair.
When we classify the morphological diversity of the TV leaflets, identification of the commissure between the anterior and posterior leaflets is important. When the TV has two posterior leaflets, the commissural cleft between the anterior and posterior leaflets is sometimes misidentified as a deep cleft of the anterior leaflet. This is because most surgeons do not observe fan-shaped chordae arising from the anterior papillary muscle and do not recognize that half of patients have a TV with two posterior leaflets. When surgeons misinterpret the commissure between the anterior and posterior leaflets, they might choose a smaller annuloplasty ring and adjust the marker on the ring to an inappropriate position, especially in patients with two posterior leaflets. A smaller ring might deform TV annulus and impose more stress on suture lines. We measured both the distance between the commissure of the septal leaflet and the area of the anterior leaflet for proper sizing of annuloplasty ring, resulting in selection of larger ring. To avoid deformation of the TV, we applied the “shoulder point fitting method” of proportional annuloplasty in all patients (18). The shoulder point is defined as the 2-o’clock position of the TV annulus, where the TV annulus is more widely dilated. This technique has a lower risk of TV annulus deformation because annuloplasty is performed toward the shoulder point (18). This method also supports patients with multiple posterior leaflets. We are convinced that proportional annuloplasty was achieved in all patients regardless of the number of posterior leaflets in this study.