Unileaflet mitral valve with one single papillary muscle: a rare congenital anomaly characterized by two- and three-dimensional echocardiography

A 49-year-old female was admitted complaining of exertional dyspnoea. Transthoracic echocardiogram showed elongated and thickened anterior mitral leaflet (AML). The posterior mitral leaflet (PML) was almost completely absent (Panel A, yellow arrow, and Supplementary material online, Video S1), leaving only a remnant of rigid valvular tissue near the P3 area, accompanied with no chordae tendineae (Panel B, arrowhead). There was only a single papillary muscle (anterolateral; Panel C, red arrow). In the A3 scallop of the AML, several tendinous cords were observed directly inserted into the basal inferior wall (Pane D, white arrow). Besides, transesophageal echocardiography (TEE) demonstrated severe eccentric mitral regurgitation (Panels E and F). From the left atrial perspective, three-dimensional (3D) TEE allowed enface visualization of the remnant of the PML in diastole (Panel G, arrowheads), as well as the prolapsed AML and the coaptation gap in systole (Panel H, Supplementary material online, Video S2). From the left ventricular perspective, 3D TEE allowed enface visualization of the normal anterolateral papillary muscle (Panel I, red arrow) along with the rudimentary chordae tendineae (Panel I, white arrow). Based on the above, the patient was diagnosed as unileaflet mitral valve (UMV) with absence of posteromedial papillary muscle and referred for surgery, but she refused finally. The UMV is the rarest entity of congenital mitral valve anomalies, few of which, as in our patient, have only one single papillary muscle. To our knowledge, this is the first detailed 2D and 3D echocardiographic depiction of the UMV with one single papillary muscle, which seems distinct from the parachute or parachute-like mitral valves. Supplementary material is available at European Heart Journal – Case Reports online. The authors thank all staff involved in this case. Consent: The authors confirm that written consent for submission and publication of this case report including images and associated text has been obtained from the patient in line with COPE guidance. Funding: This work was supported by the Sanming Project of Medicine in Shenzhen (SZSM202011013). No new data were generated or analysed in support of this research.