A 68-year-old female with a medical history of atrial fibrillation and stroke presented with increasing dyspnea and fatigue. Preoperative transthoracic echocardiography revealed severe mitral stenosis with a mean gradient of 18 mm Hg, moderately depressed right ventricular systolic function, normal left ventricular systolic function, and a patent foramen ovale (PFO). Preoperative right and left cardiac catheterization revealed widely patent coronaries, severe pulmonary hypertension with a pulmonary artery systolic pressure of 82 mm Hg, and a mitral valve area of 0.9 cm2 by the Gorlin equation. The patient was scheduled for mitral valve replacement (MVR) and PFO closure. Initial intraoperative echocardiography revealed severe thickening of the mitral valve leaflets with commissural fusion suggestive of rheumatic valvular disease, severe mitral stenosis with a mean gradient of 20 mm Hg, moderate tricuspid regurgitation, a PFO, and left atrial appendage thrombus. Left ventricular size and function were preserved, but severe right ventricular dilation with moderately reduced function was present. The patient underwent MVR with a 29-mm ATS bileaflet mechanical valve, tricuspid annuloplasty with a Medtronic Simplici-T® band (Medtronic, Minneapolis, MN) and closure of the PFO. After separation from cardiopulmonary bypass (CPB), intraoperative transesophageal echocardiography (TEE) imaging showed a bileaflet mechanical mitral prosthesis in the antianatomic position with normal occluder motion in both the 2-dimensional (D) midesophageal views as well as the 3D en face left atrial view (Video 1, Supplemental Digital Content, http://links.lww.com/AA/B82). However, 2D color flow Doppler imaging revealed moderate to severe transvalvular regurgitation based on jet area (Fig. 1A). Three-dimensional color flow Doppler en face left atrial view of the mitral prosthesis was also consistent with pathologic transvalvular regurgitation (Fig. 2A). Further interrogation with 3D echocardiography of the ventricular aspect of the mitral prosthesis detected 2 echodense masses in close proximity to the anterolateral disk (Fig. 3A). Subvalvular tissue entrapment was suspected, preventing complete closure of the anterolateral disk. Due to the definitive presence of significant pathologic prosthetic transvalvular regurgitation, the decision was made to return to CPB and rearrest the heart. Surgical inspection revealed the presence of subvalvular tissue entrapment. This was excised, and the patient subsequently weaned from CPB. TEE revealed normal prosthetic valve function with only the expected washing jets present (Figs. 1B and 2B; Video 2, Supplemental Digital Content, http://links.lww.com/AA/B83). Three-dimensional ventricular en face view of the mitral prosthesis revealed the absence of the 2 previously seen echodense masses (Fig. 3B). The patient had an unremarkable postoperative course and was discharged from the intensive care unit on postoperative day 3 and home on postoperative day 14.
Subvalvular tissue entrapment after MVR is a rare complication1 but one that should be considered in the presence of transvalvular mitral prosthetic regurgitation. Preservation of the subvalvular apparatus is a recommended technique with MVR for preservation of left ventricular geometry and function, to decrease the risk of atrioventricular disassociation and achieve improved long-term survival.2 Preservation of subvalvular tissue is more technically challenging in patients with rheumatic mitral disease due to the thickening and calcification of the subvalvular apparatus.3 Prior case reports describing prosthetic valve dysfunction secondary to subvalvular tissue interference have involved both mechanical and bioprosthetic valves in the mitral position, but the preponderance were mechanical prostheses.1–5
Prosthetic valve dysfunction secondary to subvalvular tissue entrapment may present immediately in the post-CPB period, but has also been reported to occur later in the postoperative period and even years after valve replacement.1 Other cases reporting subvalvular tissue entrapment resulting in prosthetic valve dysfunction have described abnormal motion of one of the mechanical leaflets in addition to the presence of significant transvalvular prosthetic regurgitation.1
Two previous echo rounds of cases of acute prosthetic mitral valve dysfunction in the immediate post-CPB period both describe an obvious leaflet motion abnormality seen with 2D echocardiography imaging. Chu et al.5 reported a case of subvalvular tissue entrapment that was diagnosed by 2D echocardiography after weaning the patient from CPB. Incomplete closure of one of the mechanical leaflets, significant transvalvular regurgitation, and a mass were seen preventing closure of the leaflet. Bolliger et al.4 reported a case of prosthetic mitral valve dysfunction secondary to an immobile mechanical leaflet causing significant transvalvular regurgitation in which no structural cause could be identified. Unlike these 2 previously published cases, abnormal occluder motion could not be appreciated with 2D or 3D TEE in this case. This was likely due to the fact that the subvalvular tissue created only a subtle defect in complete disk closure and underlines the importance of maintaining a high level of suspicion of subvalvular tissue entrapment in the presence of transvalvular regurgitation after MVR, even in the absence of an obvious disk motion abnormality. Three-dimensional echocardiographic examination provided excellent visualization of the ventricular aspect of the mitral prosthesis and revealed the likely culprit of the prosthetic valve dysfunction (Fig. 3).
To achieve a 3D en face view of the mitral valve from the ventricular perspective, a 2D image of the mitral valve in a midesophageal view should first be obtained that is free of artifacts. A 5-chamber or long-axis view ensures that the aortic valve will be within the 3D dataset and is useful for orientation purposes. A full-volume 3D image is acquired and subsequently cropped and adjusted to obtain an en face view of the mitral from the left atrial perspective with the aortic valve at the 12 o’clock position. This image can then be rotated on the z-axis to achieve an en face view of the mitral from the ventricular perspective. This view should also keep the aortic valve in the 12 o’clock position as recommended by American Society of Echocardiography guidelines.
Visualization of the ventricular aspect of a mechanical mitral prosthesis with 2D echocardiography can be difficult due to acoustic shadowing and reverberation artifact which occurs in the midesophageal views. Two-dimensional transgastric views are helpful in avoiding this. Both the transgastric 2-chamber and transgastric long-axis 2D views are useful for interrogation of the mitral subvalvular apparatus and may be helpful in identifying subvalvular tissue entrapment. The advantage of 3D imaging is that it also allows for unique en face views of a mitral prosthesis from both the left atrial and ventricular perspectives and provides a more comprehensive view of the valve in 1 image. Three-dimensional CFD imaging can be a useful adjunct in the evaluation of prosthetic valve regurgitation due to its ability to localize the position of regurgitant jets and distinguish normal washing jets from pathological transvalvular regurgitation. Three-dimensional echocardiography enhanced our ability to make an accurate diagnosis and guide the surgical reintervention.
Clinician’s Key Teaching Points
By Roman M. Sniecinski, MD, Kent H. Rehfeldt, MD, and Martin J. London, MD
- During mitral valve replacement, subvalvular tissue, including chordae tendinae and papillary muscles, are typically preserved to maintain left ventricular geometry. However, these tissue remnants have the potential to become lodged within the new prosthetic valve which may prevent full valve closure, resulting in pathologic regurgitation.
- Intraoperative transesophageal echocardiography (TEE) interrogation of mechanical prosthetic valve function should include visualization of prosthetic leaflet (i.e., occluder) motion and assessment of any regurgitant jets. While paravalvular (outside the sewing ring) regurgitation is always abnormal, echocardiographers must determine whether transvalvular (within the sewing ring) regurgitation represents normal “washing jets” (engineered to reduce thrombogenic potential of the valve) or is abnormal leakage due to prosthesis dysfunction. With a bileaflet mechanical prosthesis, washing jets usually appear as multiple, trivial to mild, symmetric jets usually located near the disk hinge points. In contrast, pathologic transvalvular regurgitation often appears as a larger, asymmetric jet.
- In this case, the presence of a large transvalvular regurgitant jet after implantation of a bileaflet mechanical mitral valve indicated prosthesis dysfunction even though 2D imaging revealed normal occluder motion. Using 3D imaging techniques, the authors obtained a view of the mitral valve from the left atrial perspective (i.e., an en face view), which also failed to reveal the problem. However, the 3D dataset also allowed imaging from a left ventricular perspective (i.e., looking up at the underside of the valve) that demonstrated pieces of retained subvalvular tissue that prevented normal occluder closure.
- When abnormal regurgitation is detected on postbypass imaging after a mitral prosthetic valve implantation, the intraoperative echocardiographer should not only assess its severity, but also define a mechanism for it. By providing images from different perspectives including the ventricular side of the prosthesis, 3D TEE can serve as a valuable aid in assessing prosthetic valve function
Name: Mandisa Jones Haywood, MD, FASE.
Contribution: This author helped with study design, conduct of the study, data collection, data analysis, and manuscript preparation.
Attestation: Mandisa Jones Haywood approved the final manuscript.
This manuscript was handled by: Martin J. London, MD.
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