By Michael H. Crawford, MD

Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco

Dr. Crawford reports no financial relationships relevant to this field of study.

SYNOPSIS: A large registry study of transcatheter mitral valve replacement (TMVR) in patients with degenerated mitral valve bioprostheses or failed mitral annuloplasty repairs who were at high risk for repeat surgery showed that TMVR can be performed successfully. However, the initial and long-term results are better in the degenerated bioprothesis group.

SOURCES: Yoon SH, Whisenant BK, Bleiziffer S, et al. Transcatheter mitral valve replacement for degenerated bioprosthetic valves and failed annuloplasty rings. J Am Coll Cardiol 2017; 70:1121-1131.

Webb JG, Cheung AW, Dvir D. Transcatheter mitral valve replacement when mitral surgery fails. J Am Coll Cardiol 2017;70:1132-1134.

In the 21st century, there has been a shift toward bioprosthetic surgical mitral valve replacements compared to mechanical prosthesis, which has been fueled partially by the availability of transcatheter valves to treat the inevitable bioprosthetic mitral valve degeneration or failure of a mitral annular ring and repair. However, there are few data on this application of transcatheter valve deployment. Thus, investigators created an international registry of patients undergoing transcatheter mitral valve replacement (TMVR) for degenerated mitral bioprostheses or failed annuloplasty rings and repairs. The primary endpoints were all-cause mortality at 30 days and one year. Other clinical events were secondary endpoints. A total of 248 patients with previous mitral valve surgery underwent TMVR at 25 centers, most for degenerated bioprosthesis (71%). The rest underwent failed repairs with annuloplasty rings. Women made up 57% of the patients. Their mean age was 73 years. Surgical risk scores were high (STS = 9, EuroSCORE = 27). Mitral stenosis was more common in the degenerated valve group and mitral regurgitation in the failed repair group. Two-thirds had undergone a transapical access procedure, with almost all the rest transseptal access. Compared to the bioprosthetic group, the annular ring patients experienced a lower technical success rate (83% vs. 96%; P = 0.001). Mean mitral gradients were 6 mmHg in both groups, but the annuloplasty ring group exhibited more post-procedure moderate or more mitral regurgitation (19% vs. 7%; P = 0.003). Also, the ring group demonstrated more life-threatening bleeding (8% vs.2%; P = 0.03) and acute kidney injury (11% vs. 4%; P = 0.03). The one-year all-cause mortality also was higher in the ring group (29% vs. 13%; P = 0.01). The authors concluded that TMVR is a reasonable alternative to surgery in high-risk patients with degenerated mitral bioprostheses or failed annuloplasty repairs, but the latter group demonstrated higher procedural complications and one-year mortality rates.

COMMENTARY

Once an alternative to surgery is available, off-label use is bound to happen because patients in general would rather not undergo surgery. In some cases, it makes sense for other reasons, such as degenerated mitral bioprostheses or failed repairs, because repeat surgery in patients who may be a decade older often is high risk. Therefore, it is not surprising that TMVR has been deployed in such patients. These multicenter registry data on the outcomes is welcome. Admittedly, this is not common. In this report spanning eight years of experience, each of the 25 sites in Europe and North America averaged eight procedures over the eight years of the study.

The major findings of this study are that the results are acceptable in such high-risk-for-surgery patients, and degenerated mitral bioprostheses produced better outcomes than failed annuloplasty repairs. In fact, the one-year mortality was more than two times higher in the latter patient group. Part of this was because of reduced technical success and higher early complications (bleeding, renal injury), but further problems also occurred in the ring patients. The need for re-intervention was higher with rings (17% vs. 7%; P = 0.03) and left ventricular ejection fraction was lower (44% vs. 53%; P < 0.001). Significant post-procedure MR was higher with flexible rings compared to the semi-rigid ones. Interestingly, 30-day mortality, stroke, and immediate conversion to surgery occurred at very low rates and were not different in the two groups. Finally, the access site did not affect the success of the procedure, but the transseptal approach required closure of the resulting atrial septal defect in 12%. The accompanying editorial suggested reserving TMVR for those who are not surgical candidates. Also, the editorialists noted that oral anticoagulants should be administered for at least the first three months post-TMVR since patients in this trial so treated demonstrated no mitral valve thrombi, whereas only three of the 84 treated with antiplatelet drugs demonstrated thrombi. At this time, the SAPIEN 3 valve has been approved for TMVR use. Hopefully, this will encourage the development of specific equipment for TMVR that will reduce the need for the apical approach and eliminate the need to repair the intra-atrial system with the transseptal approach.