JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY

VOL. 64, NO. 17, 2014

ª 2014 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION

ISSN 0735-1097/$36.00

PUBLISHED BY ELSEVIER INC.

http://dx.doi.org/10.1016/j.jacc.2014.08.024

EDITORIAL VIEWPOINT

Transcatheter Mitral Valve Replacement The Next Revolution?* Anelechi C. Anyanwu, MD, David H. Adams, MD

I

n this edition of the Journal, Cheung et al. (1)

for their pioneering effort, which serves as a proof-

report 2 successful deployments of a catheter-

of-concept for transcatheter replacement in the non-

mounted valve for treatment of severe func-

calcified mitral valve. This makes it probable that

tional mitral valve regurgitation. Both procedures

routine application of TMVR will be technically pos-

used a novel bovine pericardial valve designed for

sible in the near future, leading the authors to ques-

mitral valve replacement, which was mounted on a

tion whether TMVR will revolutionize therapy for

self-expanding nitinol frame and advanced through

mitral valve disease, mirroring the course of TAVR.

the cardiac apex via surgical cut down. Because of the

Will TMVR follow a similarly rapid, explosive

mitral valve’s intricate pathoanatomy and lack of a

adoption and growth trajectory as TAVR? Rather

rigid landing zone, this transcatheter mitral valve

than valve technology and technical feasibility, the

prosthesis has a complex design, including anchoring

prime determinants of TMVR’s applicability are likely

mechanisms to prevent migration into the atrium

to be some key differences that set catheter replacement of the mitral valve apart from that of the aortic

SEE PAGE 1814

during ventricular contraction. The prosthesis is not a symmetrical tube but conforms to the typical D-shape of the mitral valve annulus. In contrast, transcatheter aortic valve replacement (TAVR) prostheses have a simple, symmetrical design, with no need for ventricular anchors or specific orientation. Although prosthesis development and technical execution of transcatheter mitral valve replacement (TMVR) present unique challenges, these 2 patients with successfully deployed catheter mitral valves demonstrate that these challenges are not insurmountable. Cheung et al. are to be congratulated

valve (Table 1). Understanding these differences is critical to further development and clinical evaluation of TMVR platforms. HETEROGENEITY OF MITRAL VALVE DISEASE. Unlike

aortic valve interventions in adults, the majority of which are conducted for a single etiological diagnosis (degenerative calcific aortic stenosis), a vast array of etiologies cause mitral regurgitation (predominantly) or

stenosis,

including

congenital,

degenerative,

rheumatic, “functional” (secondary to ventricular or atrial pathology), and post-endocarditis etiologies. Within these categories, there is a wide spectrum of lesion presentation. For example, in the degenerative subset, patients with Barlow’s disease have very different valve morphology than those with simple

*Editorials published in the Journal of the American College of Cardiology

chordal rupture due to fibroelastic deficiency (2), in

reflect the views of the authors and do not necessarily represent the

terms of the degree of annular dilation, annular

views of JACC or the American College of Cardiology.

deformation, leaflet thickening, leaflet calcification,

From the Department of Cardiovascular Surgery, Mount Sinai Medical

and annular fibrosis or calcification. Within the func-

Center, New York, New York. The Icahn School of Medicine at Mount

tional category, annular characteristics differ de-

Sinai receives royalties for intellectual property related to mitral and tricuspid repair products from Edwards Lifesciences and Medtronic, Inc.

pending on various ischemic versus nonischemic

Dr. Anyanwu has reported that he has no relationships relevant to the

etiologies. Thus, a single transcatheter prosthetic so-

contents of this paper to disclose. Dr. Adams is the national co-principal

lution applicable to all etiologies is more challenging,

investigator of the US Medtronic CoreValve Trial. The Icahn School of

and prostheses or techniques might need to vary

Medicine at Mount Sinai receives royalties for intellectual property related to mitral and tricuspid repair products from Edwards Lifesciences

depending on the etiology and pathoanatomy. In

and Medtronic, Inc.

contrast, the vast majority of TAVR has been applied

Anyanwu and Adams

JACC VOL. 64, NO. 17, 2014 OCTOBER 28, 2014:1820–4

to a single disease and a consistent lesion: degenerative calcific stenosis.

1821

TMVR: The Next Revolution?

T A B L E 1 Key Differences Between TAVR and Potential TMVR Subsets

That May Influence TMVR Applicability and Adoption

NOT A DISEASE OF THE ELDERLY. Most TAVR pro-

Aortic

Mitral

cedures are performed in elderly patients, often in

Structure and shape

Less complex, circular

More complex, variable

their eighth or ninth decade of life. Thus, evaluation

Etiology, lesion

Degenerative, calcific

Multiple, typically not calcific

Anatomic risks

Left and right main coronary arteries, conduction

Circumflex artery, aortic valve, LVOT, conduction

Access for catheter therapy

Predominantly femoral

Transapical, transatrial, ? femoral

and application of this therapy were easier because there was less concern about durability and long-term implications. It was reasonably expected that a majority of high-risk elderly patients undergoing a TAVR would have a shorter life expectancy than the

Theoretical risk of late valve migration

Minimal

Possible

valve. In contrast, applying a less invasive, untested

Typical patient age

70–100 yrs

40–75 yrs

technology would be more controversial in young

Major patient comorbidity

Frequent

Infrequent

mitral regurgitation patients who may have several

1-yr mortality risk on medical treatment

High

Low

decades of life expectancy than in elderly aortic

Conventional surgical option

Valve replacement

Valve repair (replacement if not repairable)