The assessment of mitral bioprosthetic area remains a technical challenge, and its calculation by the continuity equation using transthoracic echocardiography (TTE) may be invalidated in several situations, especially after transcatheter mitral valve implantation (TMVI). This study aims to develop a new technique to measure the mitral valve area after a TMVI using a multimodal three-dimensional echocardiographic and computed tomography (CT) approach.

Among the patients hospitalized for TMVI at Bichat Hospital between June 2017 and February 2021, we selected 24 who had both a transesophageal echocardiography (TEE) and a cardiac CT after TMVI and before discharge. We performed two area measurements by planimetry: the geometric orifice area (GOA) corresponding to the area delimited by the edges of the open valve leaflets after alignment in the plane of the proximal coaptation point of the bioprosthesis leaflets; and the smallest valve area (SVA) defined by the smallest measurable area of the open prosthesis, at the free edges of the leaflets.

In our cohort, the GOA was 1.73±0.41cm² on 3D TEE and 1.75±0.42cm² on CT. The SVA was 1.40±0.31cm² on 3D TEE and 1.49±0.37cm² on CT. There was a good agreement between the two techniques for GOA and SVA (ICC>0.6, P<0.01) and a good correlation between the two measurements on 3D TEE as well as on CT (Pearson 0.88 and 0.91 respectively, P<0.001).

Our work suggests a new approach to multimodal assessment of prosthetic mitral valve area after TMVI, using 3D TEE and CT scan. Further studies are needed to complete our results, especially to confirm the feasibility and reproducibility of the measurements. It would also be interesting to correlate these area measurements with the clinical prognosis of patients after TMVI. Agreement between 3D TEE and CT measurements (Figure 1).