A 50-year-old man presented with unstable angina. Cardiac catheterization demonstrated 80% ostial stenosis of the left anterior descending coronary artery and 70% proximal stenosis of the second obtuse marginal branch. A preoperative transthoracic echocardiogram revealed normal left ventricular (LV) systolic function, no mitral regurgitation or stenosis but mentioned a mitral valve (MV) deformity comprised of an ectopic set of leaflets. No further workup was performed. He was scheduled for coronary artery bypass graft surgery. Written consent was obtained from the patient for this publication.
After induction of anesthesia, a transesophageal echocardiography probe (IE33 X7-2t xMATRIX Array probe, Phillips Healthcare, Andover, MA) was inserted without complication. The midesophageal mitral commissural view (ME MC) in 2D echocardiography (2DE) demonstrated a pivot point on either the anterior or posterior leaflet (Fig. 1A). The transgastric basal short-axis view (TG basal SAX) demonstrated this pivot point on A2 and P2 and showed 2 separate, equal-sized orifices that were side-by-side inferomedial to anterolateral (Fig. 1B). Using color flow Doppler (CFD) in the TG basal SAX view demonstrated 2 streams of blood across the MV. In the midesophageal CFD examination, there was no turbulent anterograde diastolic flow into the LV through either orifice, which would have indicated stenosis. There was trace mitral regurgitation at the A3/P3 region of the inferomedial orifice. Pulsed-wave Doppler also demonstrated no mitral stenosis with a mean pressure gradient of 1 mm Hg through either orifice. Real-time 3D echocardiography (RT3DE) examination confirmed the findings of a double-orifice MV (DOMV) (Fig. 2; Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A536). Given the apparent normal function of the MV, it was elected to continue with the scheduled coronary artery bypass graft surgery which was uneventful with a normal postoperative course.
The embryological mechanism of DOMV is thought to occur due to an abnormal union into a single structure of the dorsal endocardial and left lateral endocardial cushions during the early developmental stage.1 DOMVs are always associated with an anomaly of the subvalvular apparatus, leading to a separate tensor apparatus for each orifice.2 This abnormality was found in 1% of autopsied cases of congenital heart disease in the cardiac registry of Children’s Hospital, Boston, MA.1 It is associated with other congenital anomalies such as atrioventricular canal defect, bicuspid aortic valve, Ebstein anomaly, dysplastic tricuspid valve, interrupted aortic arch, patent ductus arteriosus, and coarctation of the aorta.3,4 DOMV is usually discovered at autopsy or as an incidental finding on imaging studies.
Trowitzsch et al.2 recognized 3 types of DOMV (Table 1). The fibrous bridge, seen in all 3 types, consists of mitral leaflet tissue and chordae tendinae.5 The classic lesion, termed the “hole” or “eccentric” type, occurs in approximately 85% of these patients, and is characterized by a smaller accessory orifice at either commissure (Table 1, Fig. 3).2 The second type, which we describe in this report, contains a complete bridge dividing the orifice into inferomedial and anterolateral parts (Table 1, Fig. 3).
2DE views, including ME MC and TG basal SAX, demonstrated the rare congenital anomaly of DOMV. The appearance of the pivot point on the MV leaflets (Fig. 1A) in the ME MC suggests that the tissue bridge is at the annular level. Unfortunately, we did not acquire a TG 2-chamber view or a TG long-axis view. These views could have been instrumental in demonstrating separate subvalvular apparatuses for each orifice as well as showing 2 separate jets on CFD coming into the LV.
Even though this patient had no hemodynamically significant valvular abnormalities associated with his complete bridge type, approximately 50% do have significant regurgitation or stenosis that needs to be surgically repaired. It is much more common to have regurgitant lesions rather than stenotic ones with double-orifice MVs. When examining these patients for mitral stenosis, it is crucial that the pulsed-wave Doppler sampling gate be placed at the tips of the MV leaflets of both orifices. If there is only 1 orifice with stenosis, the echocardiographer should calculate the total MV area (MVA) by combining the area of both orifices. If this total MVA is <1.0 to 1.5 cm2, it necessitates surgical repair. The MVA of both orifices can be calculated by the pressure half-time method or deceleration time and added together. Likewise, it can be calculated by the continuity equation but the 2 combined velocity time integrals (VTIs) of the MV orifices should be in the denominator.
where D = diameter, LVOT = left ventricular outflow tract.
Mitral regurgitation should be evaluated as if it is a single orifice valve. Severe mitral regurgitation through only 1 orifice would constitute need for surgical repair. This could be evaluated by measurement of the vena contracta width, regurgitant volume, or effective regurgitant orifice area.
Due to the en face atrial view of the MV, RT3DE allows the echocardiographer to visualize the tissue bridge more clearly. The RT3DE atrial and ventricular views demonstrated that the orifices were of equal size and were positioned anterolateral to inferomedial. Regrettably, we did not acquire a full volume 3D image that could be cropped across the valve from lateral to medial, necessary to determine the depth of the bridge. Both 2DE and RT3DE established that the tissue bridge was across the middle scallop of the posterior leaflet (P2) and middle segment of the anterior leaflet (A2). Transesophageal echocardiography can be useful in the evaluation of this anomaly regarding the specific type of DOMV, as well as whether or not there is hemodynamically significant mitral regurgitation or stenosis.
Clinician’s Key Teaching Points
By Kent H. Rehfeldt, MD, Nikolaos J. Skubas, MD, and Martin J. London, MD
- Double-orifice mitral valve (DOMV) is a rare congenital anomaly where a fibrous bridge divides the MV into 2 orifices. Many patients with DOMV are asymptomatic though approximately 50% have either mitral regurgitation or stenosis that warrants surgical intervention; regurgitation is more common than stenosis.
- DOMV is suspected by the finding of a pivot point at the level of the bridging tissue in the midesophageal mitral commissural view. Transgastric basal short-axis or en face views of the MV, obtained with 2D and 3D imaging, respectively, may be used to identify the separate orifices. In approximately 85% of cases, DOMV is characterized by a smaller, eccentric accessory orifice adjacent to one of the commissures.
- In this case, the tissue bridge at the annular level created 2 nearly equal-sized orifices. Color Doppler showed only trivial mitral regurgitation with no evidence of diastolic inflow turbulence and pulsed-wave Doppler performed separately for each orifice confirmed the lack of stenosis.
- When assessing MV area in patients with DOMV, the areas of each orifice should be combined; continuity or pressure half-time methods can be used and valve replacement should be considered if the MV area is <1.5 cm2. Regurgitation can be assessed as though the valve has a single orifice using vena contracta, regurgitant volume, or effective regurgitant orifice calculations.
Name: Nadia Hensley, MD.
Contribution: This author helped write the manuscript.
Attestation: Nadia Hensley approved the final manuscript.
Name: Rosanne Sheinberg, MD.
Contribution: This author helped write the manuscript.
Attestation: Rosanne Sheinberg approved the final manuscript.
This manuscript was handled by: Martin J. London, MD.
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