Among the congenital defects of the heart diagnosed

Atrial Septal Defect: Anatomoechocardiographic Correlation Luis Muñóz-Castellanos, MD, Nilda Espinola-Zavaleta, MD, PhD, Magdalena Kuri-Nivón, MD, José Francisco Ruíz, MD, and Candace Keirns, MD, Mexico City, Mexico This study was undertaken to enhance understanding of the anatomic abnormalities involved in atrial echocardiography 15 (10.4%) had common atrio- mixed type ASD. Of the 144 patients evaluated with septal defect (ASD) based on the anatomoechocardiographic comparison of equivalent specimens of atrioventricular connection, 105 (72.9%) had ostium ventricular canal, one (0.7%) had right absence of ASD and the echocardiograms of patients with this secundum type ASD (fossa ovalis), 10 (7%) had anomaly. Of the 72 heart specimens, two had common atrioventricular canal (2.8%) and one had ab- type ASD, two (1.4%) had ostium primum type ASD, mixed type ASD, 9 (6.2%) had superior venous sinus sence of right atrioventricular connection (1.4%). In and two (1.4%) had true fossa ovalis type ASD. This all, 46 (63.8%) had fossa ovalis type ASD, two (2.8%) series leads us to conclude that the key to successful had true ostium secundum type ASD, two (2.8%) had management of ASD depends on understanding ostium primum type ASD, two (2.8%) had superior echocardiographic images in terms of anatomic sinus venosus type ASD, and two (2.8%) had inferior specimens to provide appropriate evaluations for sinus venosus type ASD. One (1.4%) specimen had a therapeutic decisions and establishment of prognoses. (J Am Soc Echocardiogr coronary venous sinus type ASD and 14 (19.4%) had 2006;19:1182-1189.) Among the congenital defects of the heart diagnosed at our institution, 17.13% are atrial septal defect (ASD). 1,2 This corresponds to third place in clinical frequency after patent ductus arteriosus and ventricular septal defect. In the postmortem series 3 of Fontana and Edwards, ASD represented 8.7% and second place after ventricular septal defect, whereas Bankl 4 found that it occupied 3.7% of specimens. ASD can occur as a single malformation or it may be associated with other forms of congenital heart disease. A comprehension of the topographic relationship of these septal defects to cardiac structures facilitates their diagnosis. A classification of ASD is based on the septal areas involved. The interatrial septum is divided into a central portion at the level of the fossa ovale, the area between the latter and the entrance of the superior vena cava, the anteroinferior area of the septum above the atrioventricular septum, the posteroinferior area adjacent to the connection with the inferior vena cava, the highest part of the interatrial septum that separates the sinus portions of the right atrium (RA) and left atrium From the Outpatient Clinic Echocardiography, Instituto Nacional de Cardiología Ignacio Chávez. Reprint requests: Nilda Espinola-Zavaleta, MD, PhD, Outpatient Clinic Echocardiography, Instituto Nacional de Cardiología Ignacio Chávez, Juan Badiano No. 1, Colonia Sección XVI, Tlalpan, 14080 Mexico, D.F. (E-mail: niesza2001@hotmail.com). 0894-7317/$32.00 Copyright 2006 by the American Society of Echocardiography. doi:10.1016/j.echo.2006.04.030 (LA), and the area that separates the wall of the coronary venous sinus from the LA. Apart from the types of ASD included in the classification, combinations of these exist that create large septal defects that are not included in the classifications. A grasp of the topology and morphology of an ASD is invaluable to the surgeon or interventionalist in planning and executing corrective therapy. Echocardiography, especially transesophageal technique, is the diagnostic method of choice for ASDs that occur alone or in combination with other forms of congenital heart disease. 5-7 A comparison of echocardiographic examinations of adult patients with ASD and equivalent adult anatomic specimens was undertaken to achieve a greater understanding of the morphology found in different types of ASD. METHODS In all, 72 heart specimens with ASD were examined. Specimens came from the collection of normal and diseased hearts of our embryology department. The morphology of specimen hearts was analyzed using the sequential segmental system established for diagnosis of congenital heart disease. 8-10 The following anatomic elements served as references to determine the topography of the interatrial septum: on the left side the entry of the pulmonary veins, the mitral fibrous ring, and oval fold; on the right side the orifices of the inferior and superior venae cavae and coronary sinus, the cephalic limit of the atrioventric- 1182

Volume 19 Number 9 Muñóz-Castellanos et al 1183 ular septum, and the limbus fossae ovalis. Each septal defect was characterized in terms of its relationship to these anatomic structures. The interatrial septum was divided into 5 zones that corresponded to the potential sites of defects. The defects were classified according to their locations; when a defect involved two or more septal zones it was classified as mixed. From May 2002 to May 2005, 144 adult consecutive patients with ASD underwent echocardiographic examination. Studies included transthoracic and transesophageal M-mode, 2-dimensional, and Doppler techniques with an ultrasound machine (Sonos 5500, Hewlett Packard, Andover, Mass) equipped with an S3 probe and a 5-MHz multiplane transesophageal probe. Transthoracic parasternal long- and short-axis sections and apical 4-chamber views were used to evaluate the diameter of the right chambers. The size and type of defect were determined from apical and subcostal (subxyphoid) 4-chamber images. Pulmonary venous return was assessed from apical 4-chamber and suprasternal views and systemic venous return from subcostal and parasternal planes. In the transesophageal study the midesophageal 90- to 100-degree views are more helpful, particularly for defect sizing, detecting multiple defects, and assessing proximity to venae cavae. However, to assess a defect completely, 0-, 30- to 60-, and 90-degree midesophageal views are necessary to completely characterize an ASD and its anatomic relations. The echocardiographic images were chosen to illustrate the anatomic findings and were matched on that basis to establish the degree of diagnostic correlation provided by ultrasound techniques. RESULTS Anatomic Findings All heart specimens analyzed had situs solitus. Of the 72 hearts with situs solitus, two had common atrioventricular canal (2.8%) and one had absence of right atrioventricular connection (1.4%). In all, 46 had ostium secundum (fossa ovalis) (63.8%), of which 45 had complete rings and one had incomplete rings. In the former cases the ring was located away from the inferior vena cava, whereas the incomplete ring was situated in the vicinity of the orifice of this vein to the RA and was contiguous with the eustachian valve. Complete rings varied according to the extension of the septum primum, which functioned as a valve. In 8 specimens (17.8%) the valve was large and covered more than 50% of the fossa ovalis. In 9 (20%) this septum was fenestrated, in 9 (20%) the valve was small, and in 19 (42%) it was absent. Two hearts (2.8%) had true ostium secundum type ASD. Two hearts (2.8%) had Table 1 Anatomic findings Type N 72 (situs solitus) N % Complete AV canal 2 2.8 Right absence of AV connection 1 1.4 Ostium secundum (fossa ovalis) 46 63.8 True foramen ovale 2 2.8 Ostium primum 2 2.8 Superior sinus venosus 2 2.8 Inferior sinus venosus 2 2.8 Coronary venous sinus 1 1.4 Mixed 14 19.4 AV, Atrioventricular. Table 2 Echocardiographic findings Type N 144 (situs solitus) N % Common AV canal 15 10.4 Right absence of AV connection 1 0.7 Ostium secundum 105 72.9 Mixed septal defect 10 7 Superior sinus venosus 9 6.2 True foramen ovale 2 1.4 Ostium primum 2 1.4 AV, Atrioventricular. ostium primum defects situated in front of the entry of the coronary sinus; one of these was associated with mitral stenosis. Two hearts (2.8%) had superior sinus venosus type ASD located above the oval fold in the LA up to the roof of the adjacent zone of both atria and connected the sinus portions of both atria (right pulmonary vein and the entrance of the superior vena cava). Two specimens (2.8%) had inferior sinus venosus type ASDs above the inferior vena cava. One specimen (1.4%) had a septal defect between the roof of the coronary sinus and the wall of the LA. Fourteen specimens (19.4%) had mixed type defects that involved two or more areas of the septum. Ten had fossa ovalis with true ostium secundum, one had fossa ovalis with ostium primum, one had true ostium secundum and superior sinus venosus, and two included areas of the fossa ovalis with true ostium secundum and superior sinus venosus (Table 1). Echocardiographic Findings Of the 144 patients evaluated by echocardiography 94 were women and 50 were men with an average age of 30.3 years (18-73 years). Fifteen patients (10.4%) had common atrioventricular canal defects and one (0.7%) had absence of right atrioventricular connection. In all, 105 patients (72.9%) had ostium secundum type ASD. Of these, 5 had fenestrated septal defects,

1184 Muñóz-Castellanos et al September 2006 Figure 1 A, Internal view of one specimen with common atrium (CA) associated with absence of right atrioventricular connection in situs solitus. Note absence of interatrial septum, muscular floor of right atrium (R) (arrow), and loss of continuity between R and right ventricle (RV). Mitral valve (MV) shows left atrioventricular connection. B, Echocardiographic 4-chamber image shows same morphologic characteristics observed in anatomic specimen. Rudimentary RV, ventricular septal defect (VSD), and malalignment between ventricular septum (dotted line) and crux cordis is visualized (*). L, Left atrium; LV, left ventricle. whereas 22 were associated with other defects, including ventricular septal defect (5), partial anomalous connection of pulmonary veins (3), combined pulmonary stenosis and regurgitation (2), pulmonary stenosis (2), patent ductus arteriosus (2), mitral stenosis (2), Chiari network (2), ventricular septal defect and mitral valve prolapse (2), ventricular septal defect and patent ductus arteriosus (1), and prolapse of the anterior mitral leaflet with moderate mitral regurgitation (1). Ten patients (7%) had mixed type ASD, of which 8 combined ostium secundum type defects with inferior sinus venosus and two combined ostium secundum defects with extension of the ostium primum. In 9 cases (6.2%) superior sinus venosus type ASDs were found. Of these, 3 had normal pulmonary venous connection and 6 had anomalous pulmonary venous connection that was complete in 4 (to coronary sinus in one, to RA in one, to vertical vein in two) and partial in two (to RA in one and superior vena cava in one). Two patients (1.4%) had ostium primum type ASDs, both with two atrioventricular valves and two (1.4%) fossa ovalis type defects (Table 2). Anatomoechocardiographic Correlation In cases of common atrioventricular canal more than 50% of the interatrial septum is absent. A single atrial chamber is enclosed by the walls of the two atria. Common atrioventricular canal can occur in any situs; the morphology of the atrial walls and appendages provide the diagnosis. The anatomic characteristics defining situs solitus (Figure 1) can be clearly appreciated in echocardiographic image and specimen. Ostium secundum type ASD is characterized by a greater than normal dimensions of this structure during the period when it forms part of the developing heart, such that it becomes superimposed on the area of the fossa ovalis. It can vary in size and, depending on the characteristics of the septum primum, can have a small, large, absent, or fenestrated valve. In the specimen shown in Figure A, 2, a large septal defect is observed from the LA with a large ring and no valve. The echocardiographic images demonstrate the size, type, and localization of the defect. Color Doppler documents the left-toright shunt (Figure 2, B). Occasionally this type of ASD may be associated with a Chiari network evident in the anatomic specimen and on the echocardiogram (Figure 3). Figure 4 shows the fenestrated variant of this type of defect in the form of a band of tissue that separates two orifices. The two left-toright shunts can be seen on the echocardiogram. In Figure 5, a defect is apparent within the ring of the foramen ovale, which extends to the orifice of the inferior vena cava. Most of the ring is covered by the septum primum. The transesophageal echocardiographic image at 35 degrees reveals the septal defect behind the aortic valve. Figure 6 shows a view of the left chambers of the heart with an atrioventricular septal defect, a common atrioventricular valve, and a large defect that combines the ostium primum, the atrioventricular septal defect, and a ventricular septal defect. This specimen is an example of a type A Rastelli defect on the basis of the insertion of the anterior leaflets in the crest of the ventricular septum. The 4-chamber echocardiographic image demonstrates the same features as the anatomic specimen. The insertion of the anterior leaflets can be

Volume 19 Number 9 Muñóz-Castellanos et al 1185 Figure 2 A, Internal view of left atrium (LA). Note large septal defect involving areas of ostium secundum and fossa ovalis. Two-dimensional (B) and color Doppler (C) echocardiographic images show large ostium secundum type defect. ASD, Atrial septal defect; LV, left ventricle; MV, mitral valve; RA, right atrium. clearly seen, as can the ostium primum and ventricular septal defect situated between the chordae tendineae and below the leaflets. The two defects join to form a large canal. Figure 7 reveals an isolated ostium primum viewed from the LA. The proximity of the stenotic mitral valve with fusion of the leaflets at the posterior commissure is evident. The echocardiogram shows the septal defect above the separated atrioventricular valves and a perimembranous ventricular septal defect. In Figure 8, a superior sinus venosus type ASD is seen from the LA. It is noteworthy that the defect extends from the roof of the atrium beneath the connection of the right pulmonary veins. The probe points to the amplification of the fossa ovalis over the septal surface of the LA. The echocardiographic 4-chamber image also shows this type of defect. Figure 9 shows a left view of a mixed type ASD that involves the regions of the ostium primum, fossa ovalis, and superior sinus venosus and the connection of the pulmonary veins. The 2-dimensional and color Doppler echocardiographic images reveal a septal defect that includes the 3 areas described and the connection of the pulmonary veins to the LA. Figure 3 A, Internal view of right atrium (RA) shows ostium secundum type interatrial defect. Note Chiari network (arrow) inside triangle of Koch (dotted line) and above coronary sinus ostium. B, Transesophageal image at 37 degrees shows ostium secundum type interatrial defect and prominent Chiari network beneath defect (arrow). Ao, Aorta; ASD, atrial septal defect; LA, left atrium; PA, pulmonary artery; RV, right ventricle; TV, tricuspid valve. DISCUSSION The analysis of the comparison of anatomic characteristics of ASDs with their echocardiographic images was possible because the selected anatomic specimens had such characteristics that matched with the echocardiographic studies. This comparison provided a high degree of correlation between anatomy and echocardiography in this congenital heart disease. The common atrium constitutes the maximum expression of the ASD. It is defined as a defect involving more than 50% of the atrial septum. It rarely occurs as a single anomaly; it is a constant finding in dextroisomerism and levoisomerism. Each atrium can be identified by the characteristics of its walls, appendage, or venous connections. Total

1186 Muñóz-Castellanos et al September 2006 Figure 4 A, Internal view of right atrium (RA) shows ostium secundum type inter-atrial septal defect (ASD) within area of fossa ovale with two fenestrations. Transesophageal 2-dimensional (B) and color Doppler (C) images demonstrate ostium secundum type ASD with two fenestrations (arrows). Ao, Aorta; LA, left atrium. Figure 5 A, Internal view of right atrium (RA) shows atrial septal defect (ASD) within area of fossa ovalis (foramen secundum) in which remnants of left leaflet of sinus venosus can be seen adhering to interatrial septum (arrowheads). B, Two-dimensional echocardiographic image shows fossa ovalis type ASD. Note defect behind aortic valve. Ao, Aorta; IVC, inferior vena cava; LA, left atrium; PA, pulmonary artery; TV, tricuspid valve. absence of the interatrial septum defines a common atrium. The ostium secundum is so called because it is found on the septum primum superimposed on the fossa ovalis, which it augments. It is found on the central part of the atrial septum when the ring of the fossa ovalis is complete. When the ring is incomplete it extends to the orifice of the inferior vena cava and can induce the surgeon to implant the inferior vena cava in the LA during the correction of the defect. The diagnosis of an isolated ostium primum ASD is facilitated by its location in proximity to the mitral valve. In these cases there is not a cleft of the mitral

Volume 19 Number 9 Muñóz-Castellanos et al 1187 Figure 6 A, View of left chambers of heart with Rastelli s type A atrioventricular canal. Note confluence of ostium primum, actual atrioventricular defect, and ventricular septal defect (VSD) (asterisks). B, Echocardiographic 4-chamber image shows atrio-vsd with its 3 components: ostium primum, atrioventricular defect, and interchordal spaces of VSD (arrow). LA, Left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. Figure 7 A, Internal view of left atrium (LA) shows ostium primum type atrial septal defect. Note proximity of mitral fibrous ring (arrowheads). Two-dimensional echocardiographic (B) and color Doppler (C) images demonstrate ostium primum type septal defect (arrow) and two atrioventricular valves. Color-coded Doppler also documents perimembranous ventricular septal defect (VSD) with extension into inlet. LV, Left ventricle; MV, mitral valve; RA, right atrium; RV, right ventricle; TV, tricuspid valve. valve. Most cases of ostium primum ASDs are not actually isolated defects but they are commonly associated with atrioventricular septal defects. The superior sinus venosus type defect connects the sinus portions of both atria on the atrial roof. The proximity of the right pulmonary veins normally connected to the LA allows anomalous pulmonary venous drainage through the ASD as a result of blood pressure differences between the right pulmonary veins and the RA. In a partial anomalous connection of pulmonary veins into the RA this type of ASD is also present. When the pulmonary venous connection is in structures other than the RA, the ASD more commonly associated is ostium secundum type. Isolated drainage of right pulmonary veins only occurs in the presence of superior sinus venosus ASD. Hudson 11 interpreted this defect as persistence of the vestibule of the pulmonary venous sinus, such that Becker and Anderson 12 did not consider it to be a true septal defect. We included one anatomic specimen with a septal defect between the coronary sinus and the LA. This is not a true ASD but it allows a shunt similar to that observed in ASD. Mixed type ASDs are large because they involve two or more regions of the atrial septum. The most common mixed type defect includes the fossa ovalis and the ostium secundum. When the defect includes areas of the fossa ovalis and the superior sinus venosus it reaches the roof of the atria. Echocardiography provides the characteristics of the type, size, extent, and geometry of ASDs, and their relationships to cardiac structures, connection of pulmonary veins, and hemodynamic repercussions on the right heart. Therapeutic decisions and

1188 Muñóz-Castellanos et al September 2006 Figure 8 A, Internal view of left atrium (LA) of heart with superior sinus venosus type atrial septal defect (ASD). Note proximity of connection of right pulmonary veins (white arrows) with ASD (black arrow) and persistent oval fold (white arrow). B, Two-dimensional apical 4-chamber image shows superior sinus venosus type ASD that extends from atrial roof. LV, Left ventricle; RA, right atrium; RV, right ventricle. Figure 9 A, Internal view of left atrium (LA) with large atrial septal defect (ASD) involving areas of superior sinus venosus, ostium secundum, and ostium primum. Note mitral valve (MV) in inferior portion of septal defect and connection of right pulmonary vein (RPV) in superior portion. B, Two-dimensional and color Doppler 4-chamber echocardiographic images show large septal defect that involves areas of septum described in A and connection of pulmonary veins. LPV, Left pulmonary vein; RA, right atrium; RV, right ventricle. prognosis of treatment by surgery or catheterization depend on these variables. The data that this study provides should be used to select optimal patients for percutaneous or surgical closure of ASDs. Both options require accurate information regarding the anatomy of the defect, such as its maximal diameter, to choose a device with appropriate size, and the tissue rim dimensions all around the defect to optimize the placement of the device. The ASD ostium secundum and fossa ovalis types are more suitable for transcatheter closure. Surgical closure is also performed when this defect has a large size or multiple holes. The superior and inferior sinus venosus ASDs always require surgical closure, because there is not a superior rim and the device could migrate and embolize. Nonsurgical closure is contraindicated for foramen primum type, because the atrioventricular node is close to this defect and there is no inferior rim. These anatomic relationships must be kept in mind.

Volume 19 Number 9 Muñóz-Castellanos et al 1189 On the basis of these findings we conclude that the key to successful management of ASD depends on understanding echocardiographic images in terms of anatomic specimens to provide appropriate evaluations for therapeutic decisions and establishment of prognoses. This study taught us that the key for obtaining good results in the treatment of patients with ASD is a precise definition of the anatomy and a full and complete interpretation of the imaging studies. REFERENCES 1. Espino Vela J, Alvarado-Toro A. Natural history of atrial septal defect. Cardiovasc Clin 1971;2:103-25. 2. Salazar E, García-Alfogeme A, Dávila R. La comunicación interauricular: análisis de 462 casos estudiados en el Instituto Nacional de Cardiología. Arch Inst Cardiol Mex 1972; 42:4-32. 3. Fontana RS, Edwards JE. Congenital cardiac disease: a review of 357 cases studied pathologically. Philadelphia: WB Saunders Co; 1962. 4. Bankl H. Congenital malformations of the heart and great vessels: synopsis of pathology, embryology and natural history. Baltimore and Munich: Urban-Schwarzenberg; 1977, pp. 90-101. 5. Mehmood F, Verngala S, Nanda NC, Dod HS, Sinha A, Miller APO, et al. Usefulness of live three-dimensional transthoracic echocardiography in the characterization of atrial septal defects in adults. Echocardiography 2004;21:707-13. 6. Prokselj K, Kozelj M, Zadnik V, Podnar T. Echocardiographic characteristics of secundum-type atrial septal defects in adult patients: implications for percutaneous closure using Amplatzer septal occluders. J Am Soc Echocardiogr 2004;17: 1167-72. 7. Hopkins RA, Bert AA, Buchholz B, Guarino K, Meyers M. Surgical patch closure of atrial septal defects. Ann Thorac Surg 2004;77:2144-9. 8. Shinebourne EA, Macartney FJ, Anderson RH. Sequential chamber localization: logical approach to diagnosis in congenital heart disease. Br Heart J 1976;38:327-40. 9. Tynan MJ, Becker AE, Macartney FJ, Quero-Jimenez M, Shinebourne EA, Anderson RH. Nomenclature and classification of congenital heart disease. Br Heart J 1979;41:544-53. 10. Díaz-Góngora G, Attie F, Quero-Jiménez M, Muñoz-Castellanos L, Anderson RH, Tynam M. La secuencia diagnóstica de las cardiopatías congénitas. Arch Inst Cardiol Mex 1982;52: 66-78. 11. Hudson REB. The normal and abnormal interatrial septum. Br Heart J 1955;17:489. 12. Becker AE, Anderson RH. Pathology of congenital heart disease. London: Butterworths; 1981.