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Transitional Atrioventricular Canal

Joffe, Denise C., MD; Oxorn, Donald C., MD

doi: 10.1213/ane.0b013e3181a85e4b
Cardiovascular Anesthesiology: Echo Rounds
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From the Department of Anesthesiology, University of Washington Medical Center, Seattle, Washington.

Accepted for publication February 10, 2009.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.anesthesia-analgesia.org).

Address correspondence and reprint requests to Denise Joffe, MD, Department of Anesthesiology, Children’s Hospital and Regional Medical Center, 4800 Sand Point Way NE, Seattle, WA 98105. Address e-mail to denise.joffe@seattlechildrens.org.

A 39-yr-old woman presented with worsening shortness of breath and decreasing exercise tolerance. She was diagnosed with a transitional atrioventricular (AV) canal, a form of congenital heart disease, at age of 25 yr when pregnant with her first child. At that time, she was advised that she would likely need surgery if she became symptomatic.

The patient presented to our institution for repair of her defects. Intraoperative transesophageal echocardiography demonstrated mild to moderate right and left atrial and right ventricular dilation. In the midesophageal four-chamber view, a defect in the inferior part of the interatrial septum with predominately left to right low-velocity shunting was seen. The mitral leaflets were thick and tethered at their tips and a central jet of moderate mitral regurgitation (MR) was seen (see Video 1, Supplemental Digital Content 1, http://links.lww.com/AA/A3). In addition, a small jet of MR was seen to originate from the anterior mitral leaflet through a cleft (Fig. 1). In the transgastric basal short-axis view of the left ventricle, a large cleft was seen in the anterior mitral leaflet, dividing the leaflet into two (see Video 2, Supplemental Digital Content 2, http://links.lww.com/AA/A4) (Fig. 2). In the midesophageal aortic valve long-axis view, a chord was seen to arise from the anterior mitral leaflet and insert into the interventricular septum (Fig. 3). This aberrant chord did not result in left ventricular outflow tract (LVOT) obstruction. In the deep transgastric long-axis view, tricuspid valve tissue appeared to be closing what may have been a ventricular septal defect. The rest of the examination was unremarkable.

Figure 1.

Figure 1.

Figure 2.

Figure 2.

Figure 3.

Figure 3.

The primum atrial septal defect (ASD) was closed with a patch of pericardium and the mitral valve (MV) was not repaired. With hemodynamic loading conditions similar to her preoperative state, the postpump transesophageal echocardiography demonstrated an overall decrease in the amount of MR, although there was a small increase in the MR through the cleft. No flow was seen through the ASD patch.

A transitional canal consists of a primum ASD, a restrictive (small) ventricular septal defect, and a cleft MV. It is thought to result from the abnormal development of the endocardial cushions, which contributes to portions of the atrial and ventricular septum and the septal leaflets of the AV valves. It is considered to be in the spectrum between a primum ASD and a complete AV canal (Table 1). Patients are usually diagnosed in infancy when a murmur is heard. Elective repair is undertaken when the patients are in their first year of life or earlier if dictated by their symptoms.1,2

Table 1

Table 1

In a primum ASD and transitional defect, the cleft results from incomplete fusion of the anterior and posterior bridging leaflets, which normally forms the anterior leaflet of the MV and the septal leaflet of the tricuspid valve (Fig. 4). MR can originate through the cleft, at the commissures or along the leaflet edges. Valve prolapse or associated abnormalities of the subvalvar apparatus and leaflet tethering may also lead to MR.2,3 It is extremely important to search the subvalvar apparatus for aberrant chords that can cause LVOT obstruction and can complicate the repair.1–3 In addition, the LVOT can be long and narrow and contribute to obstruction. A careful assessment of the LVOT using color and spectral Doppler is necessary1,2,4

Figure 4.

Figure 4.

Although the shunt was not large, and the cleft was only mildly regurgitant, the combination resulted in sufficiently longstanding volume load and MR that the leaflets developed secondary changes and, in addition, the annulus dilated. This certainly complicated her valve disease.

Primary repair of the MV in infants with primum ASDs and transitional canals is relatively straightforward and usually consists of closing the cleft. The cleft is often closed even when there is no MR because it is believed to reduce the incidence of recurrent MR.2,4 However, reoperations for MR are more challenging because of the complex geometry of the valve and the multiple possible sources of MR.2–4 Several repair techniques have been described, including resuturing the cleft closed or closing a cleft that was left open, annular reduction, commissurotomy, and patch augmentation of deficient leaflet tissue.2–4 The shape of the MV makes it unsuitable for an annuloplasty ring. Given the young age of most of these patients at the time of reoperation for MR, aggressive attempts are made to repair the valve rather than replace it.

In this case of late primary repair, the surgeon believed that closing the cleft would distort her valve and worsen the central MR. He believed that relieving the volume load and allowing her heart to remodel would be sufficient to decrease her MR. Other surgeons have shown that the degree of postoperative MR in this group of patients is the only factor that ultimately determines the long-term incidence of recurrent MR and anything more than mild MR postbypass requires intervention.4

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REFERENCES

1. Mars GR, Fyler DC. Endocardial cushion defects. In: Keane JF, Lock JE, Fyler DC, eds. Nada’s pediatric cardiology. Philadelphia, PA: Saunders, 2006
2. Jonas RA. Comprehensive surgical management of congenital heart disease. New York, NY: Oxford University Press, 2004
3. Fraisse A, Massih TA, Kreitmann B, Metras D, Vouhé P, Sidi D, Bonnet D. Characteristics and management of cleft mitral valve. J Am Coll Cardiol 2003;42:1988–93
4. Murashita T, Kubota T, Oba J, Aoki T, Matano J, Yasuda K. Left atrioventricular valve regurgitation after repair of incomplete atrioventricular septal defects. Ann Thorac Surg 2004;77:2157–62
5. Seale A, Shinebourne EA. Cardiac problems in Down syndrome. Curr Paediatr 2004;14:33–8

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