The Role of cardIac magNeTic rEsonance in surGical Decision Making in Patients With Severe pRimAry miTral rEgurgitation (the INTEGRATE Study)

Mitral regurgitation (MR) is the second most frequent valvular heart disease and the second most frequent indication for valve surgery in Europe.

The management of patients with MV prolapse (MVP) and severe MR is mainly guided by symptoms, left ventricular (LV) dimensions and ejection fraction (EF), pulmonary artery systolic pressure (PASP) and atrial fibrillation (AF) occurrence.

According to the ESC/EACTS guidelines, surgical treatment of severe primary MR is indicated (recommendation Class I, Level B) in case of:

• symptomatic patients considered operable by the Heart Team;

• asymptomatic patients with LV dysfunction, intended as a LVEF ≤ 60% and/or LV end-systolic diameter (LVESD) ≥ 40 mm or LVESD indexed for body mass area (LVESDi) ≥ 20 mm/m2;

• low-risk asymptomatic patients without LV dysfunction (LVEF > 60%, LVESD < 40 mm, LVESDi < 20 mm/m2) when a durable result is likely, if at least 3 of the following criteria are fulfilled:

• AF secondary to MR;

• PASP value at rest > 50 mmHg;

• significant left atrium (LA) dilation, intended as LA volume index ≥ 60 mL/m2 or diameter ≥ 55 mm

• concomitant secondary tricuspid regurgitation ≥ moderate.

Surgery should be considered (recommendation Class IIa, Level B) in asymptomatic patients with preserved LV function (LVEF > 60%, LVESD < 40 mm, LVESDi < 20 mm/m2), when one of the following findings is present1:

• AF secondary to MR;
• PASP value at rest > 50 mmHg;
• LA volume index ≥ 60 mL/m2 or diameter ≥ 55 mm, provided surgical risk is low, surgery is performed in a Heart Valve Center and a durable MV repair is likely.

Preliminary data suggest that in patients with MVP, especially with Barlow's disease phenotype, left-sided chambers' enlargement and functional impairment may be disproportionate related to MR grade. Indeed, patients with BD and ≤ mild-to-moderate MR show larger LA and LV dimensions as compared to controls matched for age, gender and cardiovascular risk factors. These findings challenge the assumption that LA and LV remodeling is a direct effect of volume overload, with possible implications regarding the indication for MV intervention.

On the other hand, low mortality and good durability of valve repair has led some experienced centers to perform also early surgery, namely in any asymptomatic patient with severe MR, normal LV size and function, regular sinus rhythm, normal PASP and normal LA size, as long as surgical risk is very low and likelihood of successful valve repair is high. However, some studies have demonstrated that asymptomatic patients with severe degenerative MR can be safely followed up in experienced hands and remain free of indications for surgery for extensive periods of time. A watchful waiting strategy resulted in timely referral to surgery, excellent long-term survival, and good surgical outcomes, though requiring careful and active surveillance. Several authors agree that prospective randomized trials comparing active surveillance and early elective surgery are needed. There are also data suggesting that MR quantification by CMR has better discriminative power in identifying asymptomatic patients with degenerative MR and adverse outcomes as compared to the echocardiographic-derived integrative approach. Further prospective studies are necessary to validate these preliminary findings.