A 38-year-old woman planned to undergo open heart surgery to surgically correct a known severe MR. She had a history of undergoing percutaneous balloon valvuloplasty due to rheumatic mitral stenosis (MS) during a previous pregnancy 10 years before. At the preoperative evaluation employing 2D TTE, a tearing of the tip of a mid part of the thickened anterior mitral valve leaflet (AML) was suggested to be the main reason for a coaptation defect producing severe MR; two-chambered views using color Doppler showed a severe central MR jet projecting into an enlarged left atrium (Fig. 1, Video 1 and 2). MVR to install a bioprosthetic valve was planned preoperatively considering the technical difficulties and worse outcome of a patch repair of a large defect on the free margin of the AML.

After induction of anesthesia, a 3D-TEE probe (X7-2t transducer; Philips Healthcare, Andover, MA, USA) was placed and connected to a TEE console (iE33™, Philips Healthcare, Andover, MA, USA) and intraoperative 2D and 3D TEE examinations were performed. The 2D TEE images in the midesophageal commissural and long axis views also supported the preoperative diagnosis regarding a severe MR and systolic coaptation defect between the AML and posterior mitral leaflet (PML) (Fig. 2, Video 3 and 4). However, intraoperative real time 3D TEE provided more detailed spatial information on the MR pathology, which was entirely different from that suggested by the preoperative TTE; the "en face view" in the left atrial perspective showed a cleft in the middle of the PML, a ruptured chordae attached to the P3 scallop moving toward the left atrium during systole, and fusion of both ends of the MV commissures producing mild MS (Fig. 3, Video 5). Interestingly, the defect or cleft in the AML, which had been suggested, was not observed.

The feasibility of MVRep was reevaluated considering this new and different intraoperative diagnosis. Finally, after confirming a cleft in the P2 scallop by direct observation through atriotomy, MVRep, consisting of posterior mitral valvuloplasty with patch closure and lifting posterior annuloplasty, was successfully performed.

Post-procedural TEE evaluation including the RT 3D TEE view and post-operative TTE showed a satisfactory surgical outcome with sufficient diastolic opening greater than 3.5 cm² without any residual MR (Fig. 4, video 6).

Two-dimensional TTE and TEE provide spatial information that facilitates a thorough understanding of objective cardiac structure, pre-procedural surgical planning, and intraoperative decision-making during surgical intervention for severe MR. Regardless of the surgeon's expertise and experience, a thorough and detailed evaluation to determine the feasibility of MVRep is important during surgical intervention for severe MR, considering the better survival of MVRep, low incidence of endocarditis, better preservation of heart function, low risk of stroke and infection, and the lack of a need for long-term anticoagulant use [2,3]. Furthermore, thorough and detailed structural information is beneficial to determine the level of procedural difficulties during MVRep.

A previous report showed that intraoperative 2D TEE accurately provides MV anatomy and predicts the suitability of MVRep [1]. Independent predictors of unsuccessful MVRep include a central jet, annular calcification or severe dilatation, and extensive leaflet disease. However, due to the limitation of 2D echocardiography for delineating cardiac structures in a single 2D image, it requires multiple well-aligned 2D images to create a virtual 3D cardiac structure in the brain, and considerable effort to align the image planes. Indeed, 2D TEE and TTE require a long period of training to acquire adequate skill and knowledge for appropriate and comprehensive 2D imaging and interpretation. Furthermore, acquiring appropriate 2D images for a full evaluation of the corresponding pathology can be difficult for complex pathologies, as shown in the present case. Even the combination of preoperative 2D TTE and intraoperative TEE may not provide sufficient 2D imaging to enable a thorough understanding of MR pathology and to make a precise diagnosis. In this circumstance, 3D echocardiography or other imaging modalities are useful for evaluating the full spectrum of concurrent pathology.

As in the present case, RT 3D TEE is particularly helpful for evaluating cardiac structures located near the aligned TEE probe (perpendicular to the sonographic beam), such as MV and LA [4]; a single "en face" image from RT 3D TEE depicts the true anatomic perspective of the MV apparatus and facilitates an understanding of MR pathology in a much easier and faster manner [5,6]. After making this new diagnosis, MVRep employing PML patching was performed instead of MVR, which was the preoperatively determined surgical plan.

Although chorda repair or transfer for AML prolapse is easily and successfully performed in most cases, repairing the defect or damaged free margin of AML is much more complex and challenging, even to experienced surgeons [7], compared to techniques for repairing of PML [8]. The thickened and solid part in a longer and wider AML can hinder its homogenous motion after applying autologous or synthetic materials. This may lead to post-procedural re-intervention or a switch to MVR due to a residual or newly developed MR. Furthermore, the feasibility and success rate of MVRep in patients with rheumatic valve disease is much lower than that in patients with degenerative MV disease (about 75% vs. 95%) [2,9]. This discrepancy is probably due to a varying degree of inflammatory change in the rheumatic MV structure with extensive fibrosis and calcification of the leaflet free margin and chordal fusion, which compromises the success or outcome of MVRep. Therefore, surgeons prefer MVR to MVRep (patching) for a torn AML margin in a patient with rheumatic MV disease, as in the present case. However, despite the technical difficulties and relatively lower success rate of MVRep in rheumatic valve disease, it is recommended and preferred to MVR as a primary surgical strategy [10-12] considering that the success rate of MVRep is 75% [9].

A surgeon would be able to confirm the MV pathology and perform a similar surgical process in the absence of a new and different pre-procedural diagnosis upon intraoperative RT 3D TEE. However, the importance of a prompt pre-procedural diagnosis cannot be overemphasized considering the possible intraoperative delay to confirm the discrepancy in the diagnosis, check the feasibility of MVRep to modify the surgical strategy, and prepare surgical devices or materials.

In conclusion, the present case demonstrates the clinical efficacy of intraoperative RT 3D TEE for enabling a thorough and precise pre-procedural evaluation of severe MR and its pathophysiology and facilitating intraoperative decision-making.