Ann Thorac Surg 1998;66:1389-1393
© 1998 The Society of Thoracic Surgeons
Original articles: cardiovascular
Interventricular communication in complete atrioventricular septal defect
Kiyoshi Suzuki, MD, PhDa,
Siew Yen Ho, PhDa,b,
Robert H. Anderson, MDb,
Anton E. Becker, MD, PhDc,
William H. Neches, MDd,
Katsuhiko Tatsuno, MD, PhDa,
Shigekazu Mimori, MD, PhDa
a Department of Pediatrics, The Sakakibara Heart Institute, Tokyo, Japan
b Department of Pediatrics, The National Heart & Lung Institute, London, United Kingdom
c Department of Cardiovascular Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
d Department of Pediatrics, The Children’s Hospital of Pittsburgh, Pittsburgh, Pennsylvania USA
Accepted for publication April 27, 1998.
Address reprint requests to Dr Suzuki, Department of Pediatrics, The Sakakibara Heart Institute, 2-5-4 Yoyogi, Shibuya-ku, Tokyo 151-0053 Japan
e-mail: (ksuzuki{at}shi.heart.or.jp)
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Abstract
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Background. Little attention has been paid to whether the interventricular communication in complete atrioventricular septal defect is different beneath the superior and inferior bridging leaflets, a feature of obvious surgical significance.
Methods. We searched for a defect under the bridging leaflets and examined the valve morphologies in 98 autopsied and 86 surgical patients. Of the overall specimens, 27 were associated with Fallot’s tetralogy, and a further 20 had subaortic stenosis, aortic coarctation, or both. In the autopsied specimens, we also measured the degree of deficiency of the ventricular septum.
Results. No communication was found under the inferior bridging leaflet in 30% (29 of 98) of the specimens. All 29 hearts except two without such communications showed an undivided inferior leaflet. In contrast, all patients undergoing operation except 1 had a communication beneath both bridging leaflets (p < 0.001). The absence of a communication beneath the inferior leaflet was observed more in hearts with Fallot’s tetralogy (seven of 14) or those with subaortic stenosis, aortic coarctation, or both (eight of 18) than in those without associated anomalies (14 of 66; p < 0.01). Those with a communication under the inferior leaflet showed a greater deficiency of the inlet ventricular septum than did those without it (p < 0.001).
Conclusions. In a certain percentage of patients with complete atrioventricular septal defect, there will be no communication under the inferior bridging leaflet. Surgeons should be aware of this possibility, particularly when confronted with a patient with obstruction in either ventricular outlet.
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Introduction
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So-called complete atrioventricular septal defect (AVSD) is characterized by the presence of a common atrioventricular (AV) valve and extensive interventricular communication. In this malformation the communication is generally thought to extend under both bridging leaflets. Despite some cases in which interventricular communications were found only beneath the superior bridging leaflet [1–7], the precise incidence and clinical features of this arrangement remain to be clarified. The objective of this study, therefore, was to determine the incidence and resulting clinical implications of the finding of a common AV orifice without a defect under the inferior bridging leaflet by analysis of autopsied hearts and surgical cases.
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Material and methods
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Material
We studied a total of 184 patients with AVSD, the usual atrial arrangement, a common AV orifice, and an interventricular communication underneath the superior bridging leaflet sufficient to cause a large left-to-right shunt and pulmonary hypertension (the complete type). There were 98 autopsied specimens obtained from the pathologic collections at the National Heart and Lung Institute in London, the Academic Medical Center of the University of Amsterdam, and the Heart Museum of the Children’s Hospital of Pittsburgh. The remaining 86 patients underwent a corrective operation at the Sakakibara Heart Institute in Tokyo. The majority of the heart specimens had been collected many years ago, and scant clinical information was available. Of these specimens, 67% (66 of 98) had no other associated anomalies, whereas 18.5% (18 of 98) had subaortic stenosis, coarctation of the aorta, or both; the remaining 14.5% (14 of 98) were associated with tetralogy of Fallot. All of the surgical cases were Japanese, and the age at corrective operation ranged from 1 month to 13 years. A total of 35 were male and 51 were female, and 85% (73 of 86) had Down’s syndrome. Fifteen percent (13 of 86) were associated with tetralogy of Fallot and 2% (2 of 86) had subaortic stenosis, coarctation of the aorta, or both. Patients with isomerism of the atrial appendages, marked dominance of either ventricle, double-outlet ventricle, or discordant ventriculoarterial connections (transposition) were excluded from our study.
Measurements
We analyzed the following structures in all 184 cases: presence of an interventricular communication underneath the inferior bridging leaflet (Fig 1), associated anomalies, and morphology of both bridging leaflets. In the autopsied hearts, we also measured the lengths from the left ventricular apex to the aortic valve (outlet dimension), to the crux of the heart (inlet dimension), and the shortest length to the crest of the ventricular septum (scoop dimension) (Fig 2). From the ratios between the scoop and inlet, and scoop and outlet dimensions, we assessed the degree of deficiency of the inlet and the outlet components of the ventricular septum, respectively (scoop to inlet ratio and scoop to outlet ratio).
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Fig 1. Interventricular communication in complete atrioventricular septal defect. (Top) Large communication under both bridging leaflets. (Bottom) Lack of communication under the inferior bridging leaflet (IBL) in the presence of a large defect under the superior bridging leaflet (SBL). Both cases are classified as Rastelli type A morphology. (Ao = aorta; LV = left ventricle.)
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Fig 2. To determine the degree of deficiency of the ventricular septum, the lengths from the apex to the aortic valve (outlet), to the crux (inlet), and the shortest length from the apex to the crest of the ventricular septum (scoop) were measured. This specimen has a large interventricular communication under both bridging leaflets. (Ao = aorta; LV = left ventricle.)
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Data analysis
Data are expressed as the mean ± 1 standard deviation. Comparisons between groups were performed by Student’s t test, preceded by the F test. The 
2 test was used to compare the incidence between the noncontinuous groups. A p value less than 0.05 was considered statistically significant.
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Results
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Interventricular communication under the inferior bridging leaflet
In the 98 autopsied hearts, 29 (30%) showed a lack of communication beneath the inferior bridging leaflet in the presence of a large defect under the superior bridging leaflet (Table 1). This particular morphology was observed in 21% (14 of 66) of those without associated anomalies, whereas 44% (eight of 18) of those with subaortic stenosis, coarctation of the aorta, or both, and 50% (seven of 14) of those with tetralogy of Fallot showed this arrangement (p < 0.01). On the other hand, all patients undergoing operation except one with tetralogy of Fallot had a communication beneath both bridging leaflets (p < 0.001). In the specimens with a defect under both bridging leaflets, 72% (50 of 69) had almost the same size of communication under each bridging leaflet. In the remaining 28% (19 of 69), the communication under the inferior leaflet was smaller than that identified under the superior bridging leaflet. Such a comparison could not be made in the surgical cases because of a lack of data. We used the double-patch technique in all surgical cases, and the so-called cleft (the zone of apposition between the bridging leaflets) was sutured adequately to ensure the competence of the valve. In the specimen without a defect under the inferior bridging leaflet, the ventricular patch was placed only under the superior bridging leaflet. The atrial patch in the inferior component was sewn on to the inferior leaflet, and its superior component was sewn with the ventricular patch and the superior bridging leaflet. Repeated echocardiographic examinations revealed trivial left AV valve regurgitation both before and after the operation.
Morphology of atrioventricular valve
In the hearts with a defect under the inferior bridging leaflet, 67% (46 of 69) showed an undivided morphology, whereas the remaining 33% (23 of 69) had the leaflet partitioned by a slit or raphe. All 29 specimens but two (93%) without a defect showed an undivided morphology (p < 0.01). The only surgical specimen with this particular morphology also had an undivided inferior leaflet. The morphology of the superior bridging leaflet, in contrast, was not related to the presence or absence of the defect under the inferior bridging leaflet. In those with a communication, 57% (39 of 69) showed Rastelli type A and the remaining 43% (30 of 69) had a type C morphology. In those without a communication, 55% (16 of 29) had type A and the remaining 45% (13 of 29) had type C.
Degree of deficiency of ventricular septum
The scoop to inlet ratio in the 69 hearts with a communication under the inferior bridging leaflet was significantly smaller than in the remaining 29 without any communication (0.76 ± 0.06 versus 0.84 ± 0.06; p < 0.001) (Fig 3). All specimens with a ratio of more than 0.86 showed a lack of communication, and all hearts with a ratio less than 0.70 had a defect under the inferior bridging leaflet. The scoop to outlet ratio, however, had a significant overlap between the groups, although the mean values differed statistically (p < 0.05).
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Fig 3. The scoop to inlet ratio was significantly different between those with and without a defect under the inferior bridging leaflet (IBL) (left); however, the scoop to outlet ratio had a significant overlap between the groups (right).
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Comment
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The interventricular communication in complete AVSD has usually been considered to extend under both bridging leaflets. Our study, however, revealed that a substantial number of hearts with this malformation had a lack of communication under the inferior bridging leaflet, despite the presence of a large defect under the superior bridging leaflet. From a surgical stance, surgeons do not have to place a patch under the inferior bridging leaflet when it is firmly adherent to the ventricular septum, and the atrial patch in the inferior component is attached to the inferior bridging leaflet in the same way as in the so-called ostium primum defect (no communication under either bridging leaflet). Such a procedure is supposed to have a lower risk of injury to the nonbranching bundle of the conduction system, although the risk to the AV node may not change [8, 9].
Our study also showed that the lack of a defect under the inferior leaflet was more prevalent in those with obstruction in either ventricular outflow tract than in those without associated anomalies. Interestingly, Uretzky and colleagues [4] and Vargas and colleagues [6] reported that more than half of cases with AVSD and tetralogy of Fallot had this particular morphology. We report this type of interventricular communication associated with subaortic stenosis, coarctation of the aorta, or both. Moreover, all specimens but two with this arrangement showed an undivided morphology for the inferior leaflet. There may be a developmental relationship among the presence of communication under the inferior bridging leaflet, its specific morphology, and obstruction in either ventricular outlet [10, 11].
Maintaining the competence of the reconstructed valve is another crucial issue. Wilcox and co-workers [12] reported direct closure of the interventricular communication in patients with complete AVSD when the deficiency of the ventricular septum was less pronounced. They also stated, however, that more than half of such patients suffered from mild to moderate regurgitation of the left AV valve postoperatively, although only 1 of them had moderate regurgitation before surgery. We performed successful repair for the patient without a defect under the inferior bridging leaflet, placing the ventricular patch only under the superior bridging leaflet. Further clinical investigation is needed to clarify whether complete AVSD with this particular morphology precipitates dislocation between the bridging leaflets, and whether it therefore influences the progress of valve regurgitation before and after a corrective operation.
As described previously, the degree of deficiency of the ventricular septum is greater in those with a complete type than in those with an ostium primum defect [10, 13, 14]. This study showed that even in complete AVSD, those without a defect under the inferior bridging leaflet had a well-developed inlet part of the ventricular septum compared with specimens with such a communication, despite the same degree of deficiency of the outlet septum. Our data suggest that patients with a defect under both bridging leaflets have a severe deficiency in both the inlet and outlet components of the ventricular septum (Fig 4). Those without a defect under the inferior leaflet have a milder deficiency of the inlet part and a severe deficiency of the outlet part of the septum. From our previous studies [13, 14], we know that hearts with an ostium primum defect have a mild deficiency in both the inlet and outlet components.
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Fig 4. Interventricular communication and degree of deficiency of the ventricular septum. Hearts with a defect under both bridging leaflets (A) showed a severe deficiency in both the inlet and outlet components of the ventricular septum. Those without a defect under the inferior bridging leaflet (IBL) (B) showed a mild deficiency of the inlet part and a severe deficiency of the outlet part of the septum. From previous studies [13, 14], those with an ostium primum type (C) are considered to have a mild deficiency in both the inlet and outlet components. (Ao = aorta; LV = left ventricle; SBL = superior bridging leaflet.)
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Interestingly, the absence of a defect under the inferior bridging leaflet was more prevalent in autopsied hearts than in the surgical specimens in our series. This percentage has been observed in previous reports [1–3, 5, 7, 15]. It remains a matter of speculation, however, whether this particular morphology is related to the mortality. About half the specimens associated with obstruction in either ventricular outlet showed this arrangement, and patients with such a combination are likely to have a poorer prognosis than those without this arrangement. Other reasons could be that small defects may be closed with shrinkage of the tissue during the fixation process, or they can close as patients become older. At operation, a patch may almost always be inserted under both bridging leaflets to avoid a residual ventricular shunt without thorough observation. Another possibility is that the incidence of this arrangement reflects the difference between patients with an Asian background and those from northern Europe and the United States. An analogy to this would be patients with juxtaarterial ventricular septal defect; about 30% of the Asian population have this type of defect, whereas the incidence in children of northern European descent is only about 5% [16].
In conclusion, the interventricular communication seen in atrioventricular septal defects with a common valve orifice did not always extend under the inferior bridging leaflet. The inlet part of the ventricular septum in these instances was well developed. This particular morphology was more prevalent in those with obstruction in either ventricular outlet, so that surgeons should have a heightened awareness of this possibility, particularly when they operate on a patient with such a combination.
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Acknowledgments
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This work was supported by research grants in 1997 from the Mokichi Okada Association Health Science Foundation, Tokyo, and the Sakakibara Heart Institute, Tokyo. We also thank Mr Teruaki Kawai, Dr Kazuo Nitta, Mr Noriyuki Kawai, and Mr Tadahiko Moriyama from the MOA Health Science Foundation, and Drs Toshio Kikuchi, Yukihiro Takahashi, Yasuo Murakami, and Katsuhiko Mori from the Sakakibara Heart Institute for their help in preparing the manuscript.
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References
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- Berger T.J., Kirklin J.W., Blackstone E.H., Pacifico A.D., Kouchoukos N.T. Primary repair of complete atrioventricular canal in patients less than 2 years old. Am J Cardiol 1978;41:906-913.[Medline]
- Piccoli G.P., Wilkinson J.L., Macartney F.J., Gerlis L.M., Anderson R.H. Morphology and classification of complete atrioventricular defects. Br Heart J 1979;42:633-639.[Abstract/Free Full Text]
- Studer M., Blackstone E.H., Kirklin J.W., et al. Determinants of early and late results of repair of atrioventricular septal (canal) defects. J Thorac Cardiovasc Surg 1982;84:523-542.[Abstract]
- Uretzky G., Puga F.J., Danielson G.K., et al. Complete atrioventricular canal associated with tetralogy of Fallot. J Thorac Cardiovasc Surg 1984;87:756-766.[Abstract]
- Penkoske P.A., Neches W.H., Anderson R.H., Zuberbuhler J.R. Further observations on the morphology of atrioventricular septal defects. J Thorac Cardiovasc Surg 1985;90:611-622.[Abstract]
- Vargas F.J., Coto E.O., Mayer J.E., Jr, Jonas R.A., Castañeda A.R. Complete atrioventricular canal and tetralogy of Fallot: surgical considerations. Ann Thorac Surg 1986;42:258-263.[Abstract]
- Akiba T., Becker A.E., Neirotti R., Tatsuno K. Valve morphology in complete atrioventricular septal defect: variability relevant to operation. Ann Thorac Surg 1993;56:295-299.[Abstract]
- Feldt R.H., DuShane J.W., Titus J.L. The atrioventricular conduction system in persistent common atrioventricular canal defect. Circulation 1970;42:437-444.[Abstract/Free Full Text]
- Thiene G., Wenink A.C.G., Frescura C., et al. Surgical anatomy and pathology of the conduction tissues in atrioventricular defects. J Thorac Cardiovasc Surg 1981;82:928-937.[Medline]
- Suzuki K., Tatsuno K., Mimori S., et al. Relationship between scooping of the ventricular septum, morphology of the inferior bridging leaflet and electrocardiographic findings in atrioventricular septal defect with common valvar orifice. Cardiol Young 1996;6:37-43.
- Suzuki K., Ho S.Y., Anderson R.H., et al. Morphometric analysis of atrioventricular septal defect with common valve orifice. J Am Coll Cardiol 1998;31:217-223.[Abstract/Free Full Text]
- Wilcox B.R., Jones D.R., Frantz E.G., et al. Anatomically sound, simplified approach to repair of "complete" atrioventricular septal defect. Ann Thorac Surg 1997;64:487-494.[Abstract/Free Full Text]
- Ebels T., Anderson R.H., Devine W.A., Debich D.E., Penkoske P.A., Zuberbuhler J.R. Anomalies of the left atrioventricular valve and related ventricular septal morphology in atrioventricular septal defects. J Thorac Cardiovasc Surg 1990;99:299-307.[Abstract]
- Suzuki K., Mimori S., Murakami Y., et al. The degree of scooping of the interventricular septum influences electrocardiographic findings in atrioventricular septal defect. Cardiol Young 1995;5:262-266.
- Ebert P.A., Goor D.A. Complete atrioventricular canal malformation: further clarification of the anatomy of the common leaflet and its relationship to the VSD in surgical correction. Ann Thorac Surg 1978;25:134-143.[Abstract]
- Tatsuno K., Ando M., Takao A., Hatsune K., Konno S. Diagnostic importance of aortography in conal ventricular septal defect. Am Heart J 1975;89:171-177.[Medline]
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Abstract
Introduction
