To Clip or Not to Clip? Can We Predict Which Patients with Functional Mitral Regurgitation Will Benefit From Transcatheter Mitral Valve Repair?

Abstract

Functional mitral regurgitation (MR) is defined as leakage of the mitral valve that occurs primarily because of enlargement or dysfunction of the left ventricle or subvalvular structures, rather than a primary abnormality of the valve leaflets themselves. Functional MR increases the load on an already dysfunctional or failing ventricle, and thus may hasten the progression of heart failure. Reducing or eliminating the MR could theoretically halt or even reverse the cycle of continued pathological left ventricular (LV) remodeling. However, traditional medical wisdom has held that once the LV ejection fraction drops too low, replacing the mitral valve will take away the low resistance “pop off” chamber and increase LV afterload, potentially resulting in worsening LV failure. In addition, the requirement for cardiopulmonary bypass during surgical mitral valve replacement might also exacerbate ventricular dysfunction because of myocardial ischemia or other injury incurred during the surgery. Patients with mitral valve disease frequently have pulmonary hypertension with varying degrees of right ventricular dysfunction. The right ventricle may be particularly vulnerable to the surgical insult incurred during mitral valve repair or replacement. 1 Chrustowicz A. Simonis G. Matschke K. Strasser R.H. Gackowski A. Right ventricular dilatation predicts survival after mitral valve repair in patients with impaired left ventricular systolic function. Eur J Echocardiogr. 2009; 10: 309-313 Crossref PubMed Scopus (16) Google Scholar In a randomized trial, adding surgical mitral valve repair for ischemic (functional) MR to coronary artery bypass grafting (CABG), did not enhance reverse LV remodeling defined by reduction in LV volumes compared to revascularization alone. 2 Smith P.K. Puskas J.D. Ascheim D.D. Voisine P. Gelijns A.C. Moskowitz A.J. et al. Surgical treatment of moderate ischemic mitral regurgitation. N Engl J Med. 2014; 371: 2178-2188 Crossref PubMed Scopus (296) Google Scholar Moreover, the patients randomized to mitral valve repair in addition to CABG had higher rates of untoward events than those undergoing CABG alone. These findings provide some support for the notion that surgically fixing MR is not always beneficial, and may be detrimental when the main problem is LV enlargement and/or dysfunction.