Author + information
- David R. Holmes Jr., MD∗ ( and )
- Charanjit S. Rihal, MD
- ↵∗Reprint requests and correspondence:
Dr. David R. Holmes, Jr., Mayo Clinic, Cardiovascular Diseases and Internal Medicine, 200 First Street, SW, MB 4-523, Rochester, Minnesota 55905.
- functional versus degenerative mitral regurgitation
- mitral regurgitation
- percutaneous mitral valve repair
Analogous to transcatheter aortic valve replacement, the assessment and treatment of mitral insufficiency have assumed more central importance, primarily driven by 4 major factors: 1) The recognition that the disease is complex, consisting of multiple interrelated anatomic and physiological issues; 2) the expanding knowledge that the mortality and morbidity risk in some of these patients is high, often resulting from associated comorbidities; 3) the fact that surgical treatment for this complex group of problems is not ideal in many patients, because some patients are at high risk, with some cases even deemed to have prohibitive surgical risk or to be inoperable; and 4) the proliferation of technology aimed at addressing the issues using less invasive catheter-based approaches. When one considers these issues, it must be remembered (or perhaps, more accurately, learned) that mitral regurgitation (MR) is based on a complex set of interrelationships. These anatomic factors include the specific anatomy of the mitral valve, mitral annular, and subvalvular apparatus, such as important chordal structures, as well as regional and global left ventricular function. These anatomic relationships are in turn affected by physiological perturbations, including ventricular and annular dilation in response to volume and pressure overload on top of prior myocardial injury. Finally, the relationships between the mitral valve and closely surrounding structures, such as the circumflex coronary artery, must be kept in mind. These relationships have led to a broad grouping as functional MR versus degenerative MR. However, such groupings, although discrete and dichotomous, do not fully explain the number and overlap of the variables involved.
Given these interrelated complexities, it is apparent that 1 size for transcatheter repair or replacement will never fit all. That tenet is an essential component of the development of multiple new technological strategies.
In this issue of the Journal, Nickenig et al. (1) summarize experience with a specific technology (MitraClip, Abbott Vascular, Santa Clara, California), which has been studied widely and is now approved in both the European Union and the United States. This technology has been used in approximately 15,000 patients worldwide and has been the subject of small, carefully designed, randomized clinical trials and larger registries. The specific technology is based on Alfieri’s surgical approach, which results in “snake eyes,” or a double-inlet mitral valve. The Sentinel Registry of Percutaneous Edge-to-Edge Mitral Valve Repair fills gaps in the knowledge base, evaluating the technology in a multinational environment of 8 countries, 25 centers, and 628 patients. It does not, however, afford the reader the chance of having the full denominator of the entire set of experiences in Europe, nor does it offer a glimpse of what carefully adjudicated data by central laboratories might provide; having said that, however, it is a wonderful source of data.
There are several bottom lines. First, patients treated with this technology are elderly, highly symptomatic, and have a high logistic EuroSCORE (European System for Cardiac Operative Risk Evaluation; 20.4 ± 16.7%). These are not the sort of patients for whom there is a long roster of cardiovascular surgeons waiting outside the room to talk about scheduling for a surgical date.
Second, the most prevalent pathogenesis was functional MR, seen in 72%, whereas the remainder had degenerative MR.
Third, acute procedural success was excellent at 95.4%. Of great interest, there was no difference in procedural success between functional and degenerative MR cases. As part of this procedural success, 1 clip was implanted in 61% of the patients, whereas the remainder had more than 1 device implanted.
Fourth, in-hospital mortality was low at 2.9%, again without differences between those patients being treated for functional MR and those treated for degenerative MR. However, mortality increased dramatically to 15.3% at 1 year, which reflects the patient’s comorbid status.
Fifth, there was a dramatic reduction in the degree of MR during the procedure. At baseline for the entire group, 13.2% and 86.1%, respectively, had either moderate or severe MR, whereas immediately afterward, that had been reduced to 25.4% and 1.8%, respectively. This reduction persisted at 1 year in a subset of paired clinical study readings, which documented that only 6% had severe MR at that time. Despite this improvement, the estimated rate of rehospitalization for the entire group was 22.8%.
Sixth, there was a significant improvement in New York Heart Association functional class. This has been seen in other studies, along with improvement in quality-of-life indicators. These improvements in this elderly, frail group of patients make a marked difference in their life. Importantly, we need to bear in mind that most invasive treatments in medicine (e.g., procedures such as knee replacements) are performed to improve quality of life and functional status, and that is arguably the greatest goal of technology.
There are several very important areas that need to be addressed in the field.
First, the procedure is complex, requiring very close coordination between echocardiography, interventional cardiology, and cardiovascular surgery. As noted by Nickenig et al. (1), in 39% of patients, a second clip was needed. Detailed knowledge of 3-dimensional anatomy, including the atrial septum and the mitral apparatus, to optimize reduction in MR is required. In general, in the published literature, reduction in severity of MR is greater in patients treated with cardiovascular surgery, but the patients in whom transcatheter mitral valve repair (TMVR) is intended are at increased risk for surgery. Professional societies need to continue to define parameters of experience for individual operators and institutions to qualify for procedural performance. Training programs will continue to evolve and include simulation models, exposure to anatomic specimens, and often proctored cases. All of these elements will combine to optimize the outcome of the procedure.
Next, patient selection criteria continue to evolve. As previously mentioned, MR has been divided into 2 broad groups, degenerative and functional. At the present time, TMVR is approved in the United States for patients with significant degenerative MR who are at high risk for surgery. As described in the article by Nickenig et al. (1), the dominant problem treated was functional MR. There were some differences in outcome. Patients with functional MR required significantly more rehospitalizations. There were also differences in the severity of MR, change in left atrial size, and nonsignificant changes in left ventricular ejection fraction between the 2 groups. The extent to which these changes will help to guide patient selection is unclear. More data will be needed.
Finally, the potential concern that placement of 1 or more clips may make subsequent procedures more difficult is important. In small experiences reported to date, surgery can still be performed, if needed, after a MitraClip has been placed. If more than 1 clip has been used initially, subsequent surgical approaches may be more difficult.
This multicenter registry experience is an example of the strength of registries in evaluating the application in broader patient groups. Such an approach may serve as a template in selected circumstances for post-market approval studies, which are critical to understanding outcomes with the use of new technologies.
↵∗ Editorials published in the Journal of the American College of Cardiology reflect the views of the authors and do not necessarily represent the views of JACC or the American College of Cardiology.
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- American College of Cardiology Foundation