13-1. Cor Triatriatum
In the presence of this rare anomaly, a membrane separates the left atrium into two chambers. The proximal chamber communicates with the pulmonary veins, while the distal chamber communicates with the atrial appendage and mitral valve.
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proximal chamber of left atrium
orifice to distal chamber of left atrium
right pulmonary
FIGURE
13-1. After the cardiopulmonary bypass is established, the dilated proximal left atrial chamber is entered along the right heart border. Pulmonary veins enter this chamber, which is separated from the distal chamber by a fibromuscular septum.
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right upper pulmonary
enlarged proximal left atrial chamber
right lower pulmonary vein
FIGURE
13-2. The enlarged proximal chamber above the obstruction is exposed.
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orifice between proximal and distal left atrial chambers
FIGURE
13-3. The orifice that separates the two atrial chambers is restrictive.
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fibromuscular septum separating left atrial chambers
FIGURE 13-4. During the repair, the membrane is opened by a cephalad incision starting in the obstructive orifice.
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rim of excised septum
mitral valve
lower pulmonary vein
FIGURE 13-5. The membrane is excised, allowing free communication between the prox- imal and distal atrial chambers.
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rim of excised septum
orifice of appendage
FIGURE
13-6. The membrane region is retracted cephalad to expose the orifice of the left atrial appendage, which communicates with the distal chamber.
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remnant of excised septum orifice of appendage
mitral valve
FIGURE
13-7. The proximity of the left atrial appendage to the mitral valve in the distal
chamber is seen.
In the presence of this anomaly, a fibrous membrane located immediately above the mitral valve annulus causes symptoms similar to mitral stenosis. The pulmonary veins and left atrial appendage enter the left atrium above the membrane.
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fibrous membrane
orifice to mitral valve
FIGURE
13-8. After the cardiopulmonary bypass is established, the left atrium along the right heart border is entered. A thick membrane is present immediately above the mitral valve, which is not yet visualized.
FIGURE 13-9. The orifice through the membrane is obstructive.
orifice
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supramitral ring tissue
pulmonary vein
FIGURE 13-10. To repair the anomaly, the fibrous membrane is excised, being careful to avoid injury to the adjacent mitral valve. The thick membrane is about 5 mm above the mitral valve annulus.
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mitral valve
FIGURE 13-11. After the membrane is excised, the mitral valve is exposed. Now there is free communication between the left atrium and ventricle.
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fibrous membrane
mitral valve apparatus
FIGURE
13-12. In another patient who is on cardiopulmonary bypass, the left atrium along the right heart border is opened behind the interatrial groove. A fibrous membrane is exposed in the region of the valve annulus. Although the membrane does not protrude over most of the mitral orifice, it causes significant obstruction.
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membrane
chord and papillary muscle
FIGURE
13-13. The thin discrete membrane is intimate with the valve annulus. The mitral
valve chordal apparatus is seen immediately below the membrane.
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annulus
membrane
FIGURE
13-14. The membrane is carefully excised, being careful not to injure the annulus.
In some cases, the membranous tissue extends onto leaflet tissue. It can usually be teased away from the valve leaflet without injury to the latter.
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anterior mitral leaflet
annulus
FIGURE
