The RR is intended to remodel MA deformity, stabilize repair by reducing the tension on reconstructed valvular portions, to enhance leaflet coaptation by reducing the mitral surface area and to prevent further annular dilatation. However, it reported to reduce the dynamic annular motion affecting transvalvular blood flow in the diastole, altering ventricular/valvular interaction and impairing LV function4,8,9. It also changes the physiological saddle shape of the MA to a planar configuration. reportedly causing LVOTO by exacerbating mitral-leaflet SAM, or by narro wing the intersection angle between the aortic and the mitral-valvular planes10.
The aforementioned drawbacks of the RR pave the way for the construction of the SR eventhough it was subsequently demonstrated that RR itself was not responsible for these complications and that the LV performance actually improved after remodelling.2,11,12. Excess posterior-leaflet tissue and inadequate ring sizing (resulting in too small a ring for a too large anterior-leaflet) were identified as the culprits of LVOTO which nonetheless resolves in most cases with volume loading or by the use of beta blockers13,14.
Whilst the RR is made of titanium alloy covered by a layer of silicone rubber and polyester knit fabric, the Physio SR is constructed of Elgiloy bands separated by polyester film strips, which provide high-strength fatigue resistance and excellent spring efficiency. The latter comes in a saddle shape to conform to the bulging of the aortic root whereas the former has a kidney shape.
The SR combines remodelling by selective rigidity (a feature of the RR) at the anterior section and selective flexibility (a feature of flexible rings) at the posterior section to give a significant reduction of stress on sutures while maintaining the annulus remodelling effect15. It conforms to the configuration of the normal MA during systole, with the characteristic 3:4 ratio between the anteroposterior and the transverse diameters. It is also reported to maintain normal trans-mitral gradient pressure with excellent mid-term results16,17. After Carpentier et al report in 1995 that the SR reduces LV end systolic and end diastolic diameters whilst improving LV function, it gained popularity among MV surgeons18. Nevertheless, there is an understanding that its decreased ability to geometrically remodel especially the posterior annulus can have a detrimental effect on late repair durability. Despite its perceived superiority, several studies reported no difference in the general outcome between rigid, semi-rigid and flexible annuloplasty rings19.
Green et al.20 reported similar effects of flexible and semi-rigid rings on LV function in an animal randomized study. Manabe et al in a retrospective, propensity score matched study also demonstrated no significant difference in LVEF, LVEDD and LVESD between these two rings.21. A comparison of pericardial and SR annuloplasty also reported similar clinical and echocardiographic outcomes.1
David et al. including many others reported comparable clinical and echocardioraphical outcomes in flexible and rigid rings.4,9,22 Shahin et al. in a randomized study reported similar morbidity, mortality and LV function in the RR and SR at 5 years of follow-up.5
Our results confirm available clinical reports of good survival, freedom from recurrent significant MR and freedom from reoperation in repair for degenerative MVD.23,24,25. We recorded a low 10-year mortality (15.4%; 6.9% in RR and 8.5% in SR, p = 0.177). Our 10-year recurrent MR ≥ 2 + was also 25.5% (11.8% in RR and 13.7% in SR, p = 0.110) and so was reoperation at just 4.6% (2.6% in RR and 2.0% in SR, p = 0.167). We associated the worse clinical outcomes (though not significant) in the SR group with the larger number of patients with Barlow’s disease in this group. We also noticed a slightly higher trans-mitral pressure gradient (6.8 ± 1.93 mmHg) in the RR group than the SR group on early postoperative echocardiography which normalised on the next echocardiography.
This study in accordance with other studies indicates that recurrent MR on echocardiographic studies is more frequent than the reoperation rate indicates implying that reoperation rate is not the best parameter to estimate durability of MV repair26. A 20-year study of repair for MV prolapse concluded that the therapeutic consequences of recurrent MR may be delayed for several years after onset of recurrent regurgitation27.
At early postoperative echocardiography all patients in the RR group and 98.2% of those in SR group had no or trivial MR. Nevertheless, recurrent MR occurred at a constant rate during the following years. Similar to other studies, factors that predicted recurrent MR or reoperation were Barlow’s disease, a preoperative MR = 4 + and the use of chordal shortening28. Because degenerative process progresses even after repair, to mitigate recurrence of MR, generous resection of diseased portions of the posterior leaflet is required. Furthermore, chordae with degenerative changes should be managed by artificial chordal implantation or resection with transfer.
Following Flameng and co-workers report that when recurrent MR be it minor, moderate, or severe, is considered, only about 50% of patients remain free from more than trivial MR at 7 years after repair29, valve re-repair or replacement on a CPB rerun was routinely performed when residual MR greater than trivial was noticed on intra-operative echocardiography. In cases of significant recurrent MR after hospital discharge, the institution’s policy was valve replacement.
More than 40% of the patients showing significant recurrent MR have a new leaflet prolapse (mainly from the anterior leaflet) which is associated with continuing valve degeneration, retraction of repaired posterior leaflet, or even due to chordal rupture of elongation30. The MV undergoes these changes irrespective of the type of ring implanted. In the 14 cases of reoperation for repair failure in this study, there were 9 cases of rupture of initially shortened chordae, 3 cases of progressive anterior leaflet degeneration and 2 instances of annuloplasty suture dehiscence. Despite the substantial number of cases of Barlow’s disease, we did not find any case of LVOTO most probably because large rings (sizes > 34 mm) were used for patients with extensive leaflet enlargement and annular widening. More patients in SR than in RR received larger rings due to higher number of cases of Barlow’s disease.
When patients bearing the surgical risk (i.e., use of chordal shortening) are excluded from the analysis, our recurrence rate drops from 2.6% per year to 1.7% per year. This residual rate of 1.7% per year can be attributed to the phenomenon of valve degeneration. Recurrence rate in Barlow’s disease is 6.0% per year and 2.6% per year in FED. However, the impact of surgical risk factors (like chordal shortening, inadequate leaflet resection) is so high that after correction for these techniques, the residual recurrence rate decreases to almost that of FED (2.9 vs 2.6% per year).
Limitations. In addition to the general limitations inherent in retrospective series, the choice of classic RR or physio SR, which was left to the surgeon may represent a bias in the distribution of baseline characteristics between groups. Preoperative and postoperative data, such as annular size, tenting height, or tenting area, were available only in a small subset of patients, precluding a meaningful conclusion. The postoperative echocardiographic examinations were not performed at a similar interval of time from surgery. However, it is unlikely that this difference had an impact on MV hemodynamic performance. Finally, the results of our study cannot be automatically applied to other annuloplasty devices.