The mitral valve is the atrioventricular valve of the left heart and allows the passage of blood from the left atrium into the left ventricle, preventing its regurgitation in the systolic phase of the cardiac cycle (Fig. 1). When it loses its function it can become stenotic or insufficient. The second pathological picture can be frequently surgically repaired without replacing the valve with a prosthesis [Jouan 2015].

Since Carpentier's seminal works of the 1970s and 1980s and his pathophysiological classification of mitral disease [Carpentier 1983], mitral repair has been standardized and applied by an ever-increasing number of cardiac surgeons [Schubert et al. 2017, Allen et al. 2020]. Carpentier distinguished 3 classes of mitral disease: type 1, characterized by normal leaflet movement, due to annular dilation or leaflet perforation; type 2, characterized by excessive leaflet movement (valvular prolapse), due to papillary muscle rupture, chordal rupture or redundant chordae and type 3, characterized by restricted leaflet movement, due to rheumatic heart disease, papillary muscle dysfunction or left ventricular dilation. The valvular repair techniques consist of correcting the dysfunctional part(s) of the mitral valve and then [Cohn 1998] implanting a prosthetic ring that reshapes the mitral annulus to a physiological layout [Rausch et al. 2012], preventing a recurrence of annular dilation.

This research project is based on the implantation of the prosthetic ring before mitral repair (ring-first repair), to be able to repair the valve already in its definitive geometric arrangement.

The main objectives of implanting the ring as the first surgical step are:

a) judge the necessary corrections in the final valve geometry;

b) prevent the repaired valve tissue from being abundant (still prolapsing) or scarce (restricted) after the placement of the ring at the end of the surgical correction;

c) avoid having to add extra sutures on leaflets or valve clefts after implantation of the ring, increasing the overall stiffness of the valve.

This procedure is compatible with cases where the ring is implanted prior to valve repair anyway (artificial chordae) and can be limited in cases of anular plication or small mitral valve (rare in valvular regurgitation disease).

The research project has the following key phases:

1) measurement and implantation of the suitable prosthetic ring before repair (ring-first);

2) completion of mitral repair according to the choice of each surgeon.

The size of the ring is always based on the anterior leaflet [Bothe et al. 2013] that is usually not significantly modified by reparative surgery. Therefore, sizing can be done as well as the first surgical step. After the implantation of the ring the valve will be in its final geometric arrangement and it will be easier to judge the extent of a resection or other surgical acts.

The project can easily be developed within a prospective multicenter study with voluntary participation and may lead to a peer-reviewed publication in a surgical journal.

This project slightly alters the habits of individual operating surgeons adding the great advantage of being able to judge mitral valve repair in the definitive geometric shape of the valve itself, with a more reliable overview (Fig. 2).

Furthermore, a valve test is performed during each mitral valve repair surgery by filling the ventricle with saline solution: this inflates the valve and allows to better evaluate the type of lesion. By implanting the ring first, the valve area is reduced and the test can therefore be more reliable. Finally, it is very important to avoid adding sutures that weld parts of the leaflets or scallops together [Varghese and Adams 2011; Gillinov et al. 2005], as they stiffen the valve and alter the flow dynamics, theoretically limiting the duration of the repair.