Transcutaneous Aortic Valve Implantation in Patients with Combined Aortic Stenosis and Mitral Regurgitation: Does the Choice of Prosthesis Matter?

Mitral regurgitation (MR) of varying severity occurs in more than two-thirds of patients with severe aortic stenosis (AS) and can be functional or organic. Functional MR is caused by chamber hypertrophy and enlargement resulting from increased left ventricular afterload. Such adverse remodeling distorts the geometry of the left ventricle, causing displacement of the papillary muscles away from the annular plane. This increases the traction exerted on the chordae leading to leaflet effacement and valvular insufficiency. Indeed, echocardiographic studies in patients with severe AS and functional MR demonstrate a number of abnormalities of mitral valve deformation including increased coaptation height and tenting area. Enlargement of the mitral annulus can also occur secondary to left ventricular remodeling and disrupt normal mitral valve closing mechanics, further contributing to the development of MR. The most common cause of organic MR in patients with AS is mitral annular calcification, likely due to their advanced age. Valvular insufficiency results from extension of annular calcium beneath the ventricular surface of the posterior mitral leaflet, which elevates it toward the left atrium, reducing the amount of leaflet surface available for coaptation. A number of studies have shown that compared to organic MR, functional MR is more likely to improve following surgical aortic valve replacement (SAVR) and transcutaneous aortic valve implantation (TAVI). In 1 surgical series, improvement occurred in about 80% of patients with functional MR, whereas almost two-thirds with organic MR demonstrated no change or worsening. In addition, functional mitral valve disease is an independent predictor of MR improvement (along with pulmonary artery pressure <60 mmHg, absence of atrial fibrillation, and mean transaortic gradient 40 mmHg) both in patients who have undergone SAVR and TAVI. The burden of MR in patients with AS is determined by 2 factors: the area of the mitral regurgitant orifice and the driving pressure across this orifice (transmitral pressure gradient). The reduction in left ventricular systolic pressure which follows TAVI and SAVR decreases MR whether it is functional or organic. By contrast, restoration of LV geometry (reverse remodeling), following TAVI or SAVR, has a greater impact on the severity of functional MR. There are currently 2 widely available devices used for TAVI: the Edwards Sapien valve (Edwards LifeSciences, Irvine, CA, USA) and the CoreValve (Medtronic, Minneapolis, MN, USA). An important difference between these is the propensity of the latter to protrude into the left ventricular outflow tract. This can interfere with the motion of the anterior mitral leaflet, secondary chordae, or the anterior mitral annulus causing MR, or rarely, mitral stenosis. Figure 1 shows a CoreValve prosthesis with its ventricular end seated deeply in the left ventricular outflow tract causing significant MR. One study correlated greater amounts of MR with deeper positioning of the CoreValve; however, this is controversial. There are currently limited data available to determine the optimal prosthesis for patients with combined AS and MR. Studies to date have demonstrated more favorable outcomes using Address for correspondence and reprint requests: Jeffrey J. Silbiger, M.D., Echocardiography Laboratory, Department of Cardiology, Mount Sinai Services, Elmhurst Hospital Center, 79-01 Broadway, Room D3-24C, Elmhurst, NY 11373. Fax: +718-334-3236; E-mail: jeffrey.silbiger@mssm.edu