Introduction

The mitral valve is a complex structure incorporating leaflets, chordae tendinae, papillary muscles, and annulus, and requires synchronous function of these multiple elements, along with the left ventricle, to properly direct blood flow from the left atrium to the left ventricle. When even just a single component of the mitral apparatus fails, the valve becomes incompetent, allowing regurgitant flow into the left atrium.

Severity of mitral regurgitation (MR) is associated with worsening survival. Consequently, correction of severe MR is often recommended for patients with symptoms or even in asymptomatic MR with signs of left ventricular dysfunction (ejection fraction less than 60% or end-systolic diameter greater than 40 mm).[1],[2],[3] Historically, mitral valve replacement was performed any etiology of MR; however, significant evidence has shown that patients with degenerative MR, that is, MR arising from structural defects in the mitral valve apparatus, demonstrate better survival and ventricular function with mitral valve repair.[4],[5] Based on recent evidence, patients with functional MR, that is, pathology arising from left ventricular insult that interferes with proper left ventricular function and thus also proper function of the mitral apparatus, may have better correction of MR with mitral valve replacement.[6]

Mitral valve pathology is thought to be the most common valvular abnormality, with an estimated prevalence of 10% in patients over age 75.[3] Although correction of MR may be justifiable, surgery is often avoided because of patients’ comorbidities and increased surgical risk. As many as 50% of patients are denied mitral valve surgery, with impaired ejection fraction, older age, and the presence of multiple comorbidities cited as the most common reasons for denying surgery to patients.[7] With these concerns about concomitant comorbidities and patient intolerance of surgical intervention, as well as challenges in long-term recovery, there has been significant investment in less invasive and percutaneous intervention on the mitral valve.