A Rare Cause of Severe Bioprosthetic Transvalvular Regurgitation Diagnosed by Transesophageal Echocardiogram

Graphical abstract


INTRODUCTION
Mitral valve (MV) replacement (MVR) with a bioprosthetic valve is a widely used treatment for mitral regurgitation (MR).Complications with bioprosthetic MVR immediately postimplantation are rare and include paravalvular leak, stuck leaflets, and valve malposition and damage, among other considerations. 1We present a patient with severe transvalvular regurgitation after bioprosthetic MVR diagnosed with transesophageal echocardiogram (TEE) due to unintended suture encircling of a replacement valve strut.

CASE PRESENTATION
A 64-year-old woman with a medical history of hypertension, diabetes mellitus type 2, and MV prolapse with severe MR underwent a MV repair with annuloplasty via right minithoracotomy approach 1 month ago.The patient presented with new-onset atrial fibrillation and progressively worsening dyspnea on exertion and was found to have recurrent severe MR post-MV repair.They returned for right minithoracotomy MVR and left atrial appendage ligation.
The patient underwent an uneventful general endotracheal anesthetic.Initial intraoperative TEE revealed severe MR and normal left ventricle function.Due to scar tissue and lung adhesion to the chest wall, the right minithoracotomy approach was abandoned and converted to open sternotomy.The mitral ring was successfully removed, and the MV was replaced with a 29 mm bovine pericardial tissue valve sutured in place without hand sutures using the COR-KNOT (Minogue Medical) automatic titanium fastener system.In preparation for separating from cardiopulmonary bypass (CPB), the heart was filled, CPB flow was decreased, and the MV was evaluated by TEE.Moderate MR was noted with the anticipation that this would improve upon complete filling of the left ventricle and separation from CPB (Figure 1, Video 1).The patient was successfully separated from CPB with vasopressor and inotropic support, and the sternot-omy was closed.Due to increasing vasopressor requirements prior to skin closure, repeat operative TEE was done to reevaluate the MVR.Transesophageal echocardiogram revealed worsening severe central MR (Figure 2, Video 2).Three-dimensional imaging of the MV showed restricted movement of 2 of the leaflets, causing incomplete coaptation during systole (Figure 3, Video 3).
Although the etiology of the restriction was unclear, it was decided to reopen the chest and replace the dysfunctional valve with a different 29 mm porcine valve without complications.Reevaluation of the new valve showed a well-functioning bioprosthetic MV without any paravalvular or transvalvular leak.The patient tolerated the procedure well, was extubated to nasal cannula at the end of the case, and was transported to the cardiac intensive care unit.The surgeon noted on reopening that a suture loop had snared over one of the valve posts, most likely being the culprit for the significant intravalvular regurgitation, as it tethered 2 of the bioprosthetic leaflets in a manner that restricted its full closure.Postoperative evaluation of the gross specimen revealed where one of the sutures had encircled the replacement valve strut causing disruption of the commissure of 2 of the valve leaflets and its tethering (Figure 4).

DISCUSSION
This case report describes a rare complication of severe transvalvular regurgitation after bioprosthetic MVR due to suture snare of a strut causing restricted MV leaflet motion at a valve leaflet commissure and incomplete valve leaflet coaptation during systole.The COR-KNOT device used to suture the bioprosthetic valve into place has been shown to reduce CPB time, aortic cross-clamp time, and operative time in addition to improved suture strength (compared to hand- View the video content online at www.cvcasejournal.com.tied sutures). 2,3However, there have been reports of the COR-KNOT being associated with prosthetic valvular regurgitation.In a study of COR-KNOT complications compared with hand-tied sutures, the incidence of transvalvular regurgitation after MVR with the use of COR-KNOT sutures is as high as 4.5%. 4In general, the most frequent cause for immobilization of bioprosthetic valve leaflets is due to remnants of the subvalvular apparatus or retained native valve structures interfering with valve closure. 1,5In a case report by Fujiwara et al. 6 , paravalvular and transvalvular leak was noted on TEE postprosthetic valve MVR and was caused by a suture loop jamming around the stent of the bioprosthesis.Takeshita et al. 7 describe a case of a stuck bioprosthetic valve leaflet due to a loop of suture caught on a strut beneath the valve, likely caused by malrotation of the valve holder during placement into the mitral annulus.

VIDEO HIGHLIGHTS
It is important to emphasize the role of TEE in the interrogation of a newly placed bioprosthetic heart valve.Immediately post-CPB, intraoperative TEE is an important diagnostic and therapeutic tool in valve replacement surgery and should be widely implemented. 8In the case presented above, upon preliminary evaluation of the MVR with two-dimensional TEE, moderate MR was noted (Figure 1).Upon imaging reevaluation, after the case, it appears that the initial images were taken initially of the plane, thus misinterpreting the severity of the regurgitant jet.After completely separating from CPB and sternal closure, due to worsening hemodynamics, the heart and valve were reassessed and worsening MR was noted.Further interrogation of the valve with three-dimensional imaging revealed restriction and abnormal function of 2 leaflets of the valve.In addition, on twodimensional imaging (Video 1 and Video 2), 1 of the leaflets is abnormally folding in both systole and diastole, which provides imaging evidence for the mechanism of the MR.In this case, TEE was an important diagnostic aid in the search for a source of the patient's worsening hemodynamic stability.This problem might have been identified earlier if a more comprehensive imaging evaluation had been done before sternal closure.Prompt diagnosis of the snared strut allowed for the replacement of the dysfunctional valve in a timely manner, avoiding further hemodynamic compromise.

CONSENT STATEMENT
Complete written informed consent was obtained from the patient (or appropriate parent, guardian, or power of attorney) for the publication of this study and accompanying images.

Video 1 :
Two-dimensional TEE, midesophageal 4-chamber view (foreshortened) with color-flow Doppler, demonstrates MR and the abnormal indentation on the prosthetic leaflet.Video 2: Two-dimensional TEE, midesophageal 4-(left; 0 ) and 2-(right; 90 ) chamber zoom views with color-flow Doppler, demonstrates severe valvular MR following bioprosthetic MVR.Video 3: Three-dimensional TEE, volume-rendered short-axis en face display (surgeon's view) of the MVR from the atrial perspective, demonstrates the folding of the anterolateral and posteromedial leaflets resulting in restricted leaflet motion.

Figure 4
Figure 4 Gross images of the explanted bioprosthetic valve demonstrate the snared strut (arrows) on the ventricular (A) and atrial (B) sides, causing disruption of leaflet commissure and leaflet folding leading to restricted movement.