Abstract
Background
Accurate identification of the right fibrous trigone is essential for durable mitral annuloplasty. Misidentification may lead to annuloplasty ring malposition and early ring dehiscence.
Case Summary
A 24-year-old man with severe mitral regurgitation due to medial P2-P3 billowing underwent minimally invasive mitral valve repair with implantation of a 34-mm annuloplasty ring. On postoperative day 12, transesophageal echocardiography revealed ring dehiscence at the right fibrous trigone despite preserved valve competence. Reoperation confirmed incomplete trigonal engagement, and the ring was replaced with secure anterior extension of sutures. The postoperative course was uneventful.
Discussion
This case illustrates an uncommon mechanism of ring dehiscence, misidentification of the right fibrous trigone, highlighting the importance of anatomical orientation and tactile feedback during annuloplasty.
Take-Home Message
Secure trigonal engagement is critical to prevent ring malposition and dehiscence.
Key words: complication, MICS MVP, ring dehiscence
Visual Summary
Visual Summary.
Identification of the Trigone-Commissure Relationship
(A) The right fibrous trigone usually exists medially from the posterior commissure. (B) In the current case, incomplete annuloplasty ring engagement occurred because of failure to capture the right fibrous trigone. (C) Correct ring attachment with adequate trigonal engagement.
Mitral valve repair (MVr) is the standard surgical treatment for degenerative mitral regurgitation. With the evolution of minimally invasive cardiac surgery (MICS), video-assisted MVr through a right mini-thoracotomy has become widespread. Annuloplasty with an appropriately sized ring is crucial for long-term durability,1 and failure of ring anchoring—ring dehiscence—remains a significant technical complication. Although dehiscence most commonly occurs along the posterior annulus, particularly at the P3 segment,2,3 anatomical misidentification of the right fibrous trigone may result in atypical dehiscence patterns. We report a case of acute-phase ring dehiscence caused by failure to correctly capture the right fibrous trigone during MICS-MVr.
Take-Home Messages
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The right fibrous trigone cannot be directly visualized and must be identified using anatomical orientation and tactile feedback.
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Inadequate trigonal engagement may lead to atypical ring malposition and early dehiscence, regardless of surgical approach.
Case Presentation
A 24-year-old man was referred for surgical management of progressive mitral regurgitation. Transesophageal echocardiography revealed medial P2-P3 billowing with severe regurgitation and annular dilatation (anteroposterior diameter: 37 mm, transverse diameter: 44.5 mm). No comorbidities were present.
Surgical Procedure
Video-assisted MICS-MVr was performed via a right fourth intercostal space mini-thoracotomy under peripheral cardiopulmonary bypass. After left atriotomy and valve exposure, P3 triangular resection was performed, followed by reconstruction with 5-0 running sutures. A 34-mm Physio Flex ring (Edwards Lifesciences) was implanted using 10 interrupted U-stitches (Figure 1). Intraoperative transesophageal echocardiography confirmed successful repair without residual regurgitation.
Figure 1.
Physio Flex Attached Inappropriately, Especially in the Right Fibrous Trigone Area (Arrows)
Postoperative Course
The patient was extubated 3 hours after surgery and was transferred to the general ward on postoperative day 2. Transthoracic echocardiography on day 4 demonstrated no mitral valve regurgitation. However, transesophageal echocardiography on postoperative day 12 revealed ring dehiscence at the right fibrous trigone, although no regurgitation was detected. Because early recurrence of mitral valve regurgitation was anticipated, reoperation was recommended and accepted.
Reoperation
Reoperation was performed via median sternotomy approach. Retained adhesions were mild. Through a superior transseptal approach, inspection of the mitral valve confirmed ring detachment at the right fibrous trigone (Figure 2). The stitching line of the initial repair had failed to capture the true right fibrous trigone, and the physiologic position of the Physio Flex ring was shifted toward the posterior commissure. The ring was removed, and 12 new U-stitches were placed circumferentially before implanting a 33-mm Tailor ring (Abbott). Intraoperative echocardiography demonstrated no residual regurgitation and appropriate ring fixation. The postoperative course was uneventful, and the patient was discharged on postoperative day 11.
Figure 2.
Intraoperative Findings at Reoperation Demonstrating Ring Dehiscence at the Right Fibrous Trigone
Discussion
Ring dehiscence occurs in 1% to 2.3% of mitral valve repairs for degenerative mitral regurgitation,2,3 and its incidence appears to decline with increasing surgical experience.3 Although most cases are attributable to technical factors, several studies have also clarified distinct anatomical regions that are predisposed to this complication. Dehiscence most frequently involves the posterior annulus—predominantly the P3 segment—followed by P2 and P1, with 77% of events manifesting in the acute (<30 days) or early (<1 year) postoperative period.4
Experimental work by Pierce et al5 demonstrated that posterior annular tissue contains substantially less collagen and has inferior tensile strength compared with the tissue spanning the anterior annulus and trigones, thereby explaining the vulnerability of the posterior annulus to mechanical failure. Their subsequent investigations revealed that suture forces on annuloplasty rings vary significantly with knot-tying technique, and that selecting a ring smaller than the native annulus amplifies systolic stress imposed on the posterior annulus.6 A systematic review by Arjomandi Rad and colleagues7 showed that rigid and semirigid rings are associated with higher dehiscence rates than flexible rings, whereas partial versus complete rings do not differ significantly in incidence.
These observations underscore the necessity of placing sutures correctly within the native annulus and selecting an appropriately sized ring to minimize dehiscence risk. The mitral annulus is in fibrous continuity with the aortic valve, anchored at both ends by the right and left fibrous trigones—dense collagenous structures that serve as key load-bearing components of the aortomitral valvar complex. Because trigone position varies with the anatomical relationship between the aortic and mitral valves,8 the right fibrous trigone—continuous with the membranous septum and forming part of the central fibrous body—is particularly sensitive to this anatomical variability.9
In a morphological study of 100 normal hearts, Jatene et al10 demonstrated that the commissure between the noncoronary and left coronary sinuses of the aortic valve aligned with the midanterior mitral annulus in 47% of cases, the anterior commissure in 49%, and the posterior commissure in only 4%, suggesting that in approximately half of individuals, the right fibrous trigone lies medial to the posterior commissure. Modern computed tomography and magnetic resonance imaging corroborate this leftward displacement of the trigone.11
The Physio Flex ring was developed to accommodate such anatomic variability. Its open, asymmetric design relieves stress from the aortomitral curtain while facilitating secure engagement of a right fibrous trigone that may be shifted medially. Consequently, accurate identification of the trigone-commissure relationship is indispensable when implanting this device.
In the present case, the minimally invasive approach produced a vertically compressed field, hindering full appreciation of the annular geometry. As a result, sutures intended for the right fibrous trigone were placed too laterally, terminating at the posterior commissure. This misalignment placed off-axis stress on the ring, ultimately leading to focal dehiscence at a site not typically considered high risk.
Although precise annuloplasty suturing and appropriate ring sizing are essential in all repairs, these factors assume heightened importance when implanting asymmetric rings such as the Physio Flex. Failure to engage the true trigone may result in atypical patterns of dehiscence, as observed in this patient.
Conclusions
Secure anchoring of the annuloplasty ring depends on accurate identification of the right fibrous trigone. Minimally invasive exposure may distort spatial perception, increasing the risk of atypical ring dehiscence. Surgeons should maintain heightened awareness of trigonal anatomy, especially when implanting asymmetrical rings such as the Physio Flex.
Funding Support and Author Disclosures
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Footnotes
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.
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