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Search this website Echocardiographic Evaluation of Common Atrioventricular Canal Defects Authors LOG IN TO MY ACCOUNT ABOUT MEETINGS EDUCATION MEMBERSHIP STS CCAS DATABASE NEWSLETTERS LINKS ADVAN.Search this website Echocardiographic Evaluation of Common Atrioventricular Canal Defects Authors LOG IN TO MY ACCOUNT ABOUT MEETINGS EDUCATION MEMBERSHIP STS CCAS DATABASE NEWSLETTERS LINKS ADVAN.
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ABOUT MEETINGS EDUCATION MEMBERSHIP STS-CCAS DATABASE NEWSLETTERS LINKS ADVANCED TRAINING FOR PATIENTS & PARENTS SPONSOR A MEMBER Echocardiographic Evaluation of Common Atrioventricular Canal Defects Authors Nelson Burbano, MD Clinical Instructor in Cardiac Anesthesia, Harvard Medical School Department of Anesthesiology, Pain and Perioperative Medicine Boston Children’s Hospital and Brigham and Women’s Hospital nelson.burbano-vera@childrens.harvard.edu nburbano-vera@partners.org James A DiNardo, M.D.,FAAP Professor of Anaesthesia Harvard Medical School Chief, Division of Cardiac Anesthesia Francis X McGowan, Jr., M.D Chair in Cardiac Anesthesia Boston Children’s Hospital james.dinardo@childrens.harvard.edu Definition There is variability in the terminology used to describe these defects (name, definition and classification) depending mainly on the nomenclature system that is utilized (“Van Praaghian” or “Andersonian,” Table 1) Common atrioventricular canal (CAVC) is also referred to as atrioventricular septal defect, common atrioventricular orifice, atrioventricularis communis and endocardial cushion defect [1, 2] After integrating both Dr Van Praagh and Dr Anderson’s approaches, CAVC can be understood as a group of cardiac defects due to deficiency of structures derived from the endocardial cushions (atrioventricular septum and septal aspect of the leaflets of the mitral and tricuspid valves), characterized morphologically by a single atrioventricular junction or connection and a common atrioventricular valve (AVV) with one or two atrioventricular orifices Anatomy Structures derived from the endocardial cushions during embryogenesis include (Figure1): [1, 3] Atrioventricular septum This has two components, atrial and ventricular Atrial component of the atrioventricular septum or canal portion of the atrial septum This is the portion of the atrial septum located between the anterior-inferior margin of the fossa ovalis and the common AVV It results from a growth of endocardial cushion tissue toward the posterior wall of the common atria (it is not septum primum!) The absence of this component results in an ostium primum atrial septal defect (ASD) Ventricular component of the atrioventricular septum, canal portion of ventricular septum or inlet septum This is the muscular tissue that lies posterior immediately under the septal leaflet of the tricuspid valve (TV) extending anteriorly into the vicinity of the membranous septum It results from a growth of endocardial cushion tissue toward the apex of the heart The absence of this component gives the ventricular septum a “scooped-out” appearance and results in a ventricular septal defect (VSD) of the AV canal type (also inlet or posterior VSD) There may be a variable degree of underdevelopment of the inlet septum, so the VSD component of the canal can range from small and restrictive to large and unrestrictive.[4] Septal aspect of the leaflets of the tricuspid and mitral valves These result from the growth of endocardial cushion tissue toward the lateral (right and left) aspect of the annulus of the common AVV As compared to a normal heart, the tissue deficiency at this level results in an abnormal division or “clefts” of the septal leaflets of the common AVV where the septal components of the two valves fuse to form a separate superior common leaflet (superior bridging) and an inferior common leaflet (inferior bridging) There are major abnormalities in the morphology of the base of the heart in CAVC that are not limited to the atrioventricular valves alone [2, 5] The common AVV is characterized by having a single atrioventricular junction or connection (single fibrous AV annulus), a left component (mitral valve in the normal heart), a right component (tricuspid valve in the normal heart), and typically five leaflets (although the number of leaflets is variable – a superior bridging leaflet, an inferior bridging leaflet, a left mural leaflet and two right mural leaflets) The superior and inferior bridging leaflets cross from side to side over the crest of the ventricular septum, and their morphology and attachments vary The presence of a large, single, ovalshaped AV annulus dislodges the aortic valve annulus from its normal “wedged” position between the annuli of the TV and MV (Figures and 3) The anterior and superior displacement of the aortic valve by the common AVV makes the outlet dimension of the LV greater than the inlet dimension and elongates the left ventricular outflow tract (LVOT, Figure 4) This anatomic abnormality is partially responsible for the characteristic “gooseneck deformity” initially described in the left ventriculogram but also appreciated in echocardiography Van Praagh Classification of CAVC [1] Partial (Figures and 6, Videos 2, 3, 4, 5, 6, 7, 8) This form of CAVC is characterized by a large interatrial communication in the canal portion of the atrial septum (ostium primum ASD), a “cleft” in the left component of the common AVV (anterior mitral leaflet of the MV in the normal heart) and abnormal elongation of the LVOT As in other forms of CAVC, there is a single AV annulus and a common AVV with two AV orifices and with left and right components that share a common hinge point at the crux of the heart Although there is a variable degree of deficiency in the ventricular component of the AV septum, this is completely closed by a tongue of connective tissue composed of AVV tissue and chords attached to the crest of the ventricular septum, such that no interventricular communication exits The abnormal implantation of the “common hinge point” of the septal aspect of the right and left components of the common AVV (septal leaflet of the TV and anterior mitral leaflet of the MV in the normal heart) is a consequence of the deficiency of the ventricular septum Abnormal elongation of the LVOT is seen in this and other forms of CAVC and constitutes a risk factor for LVOT obstruction, especially when there are chordal attachments from the left component of the superior bridging leaflet to the ventricular septum In the opinion of some experts, the tissue deficiency in the septal aspect of the right and left components of the common AVV does not represent real “clefts,” but rather a defect in the zones of apposition between the superior and inferior bridging leaflets at the ventricular septum Typically this is the site of origin of AVV regurgitation (Videos 4, 5, 6, 7, 8) Echocardiographically, there is a clear difference between this defect and the isolated cleft of the anterior mitral leaflet of the MV seen in the adult population In the later, the cleft most frequently extends along the mid point of the anterior mitral leaflet (A2) towards the aortic valve In CAVC on the other hand, the “cleft” extends from the mid point of the “potential anterior mitral leaflet” towards the atrial septum (from A2 to the posteromedial commissure) This and the intermediate form of CAVC are the only two lesions where the common AVV has two orifices Transitional (Figure and 3, Video 13, 14, 15, 16, 17) This form of CAVC is characterized by a large interatrial communication in the canal portion of the atrial septum (ostium primum ASD) and a pressure restrictive interventricular communication in the canal portion of the ventricular septum (inlet VSD) Typically there are multiple short, dense chord attachments from the crest of the ventricular septum to the undersurface of the superior and inferior common leaflets of the common AVV and multiple small shunts through these attachments and the septum Other important features of the transitional form of CAVC include single AV junction or connection, common AVV with single orifice, and “common hinge point” of implantation of its septal components Intermediate This rare form of CAVC is characterized by an interatrial communication in the canal portion of the atrial septum (ostium primum ASD), a divided common AVV with two orifices due to fusion in the midline of the superior and inferior bridging leaflets and a large, unrestrictive interventricular communication in the canal portion of the ventricular septum (inlet VSD) Complete (Figure and 8, Video 9, 10, 11, 12) Complete CAVC presents in two thirds of all cases as a single cardiac defect or associated with minor cardiac abnormalities and in one third associated with other major cardiovascular abnormalities[6] This form of CAVC is characterized by a large interatrial communication in the canal portion of the atrial septum (ostium primum ASD) and an unrestrictive interventricular communication in the canal portion of the ventricular septum (inlet VSD) Other features of this form of CAVC include single AV junction or connection, common AVV with single orifice and left and right components, and “common hinge point” As in the other forms of CAVC, the ASD is located anteriorinferior to the margin of the fossa ovalis and adjacent to the AVV The VSD is posterior along the septal leaflet of the AVV extending into the vicinity of the membranous septum, giving the ventricular septum a scooped-out appearance (Figure 4) The common AVV has a variable number of leaflets with at least one mural leaflet positioned exclusively over each ventricle, and superior and inferior leaflets that bridge the crest of the ventricular septum Due to deficiency of the inlet portion of the ventricular septum, the common AVV sits in a more apical position within the ventricular mass, which decreases the length of the long axis of the LV The superior bridging leaflet causes anterior and superior displacement or “unwedging” of the aortic annulus and elongation of the LVOT (Figure 4) Unlike the normal heart, the aortic annulus is not located between the septal leaflets of the TV and MV, but superior to the bridging leaflet of the common AVV (Figures and 3) While typically the inferior bridging leaflet has extensive chordal attachment to the crest of the ventricular septum, attachments and degree of bridging of the superior leaflet is variable and gives origin to the Rastelli classification Rastelli et al have divided the complete form of CAVC into three types based on differences in the configuration, relationship, and attachments of the anterior leaflet of the common AVV [6] Rastelli Type A (Figures and 9, Videos 20 and 21) This is the most common type of complete CAVC (75%) The superior bridging leaflet is completely divided from the free edge to the annulus at the level of the ventricular septum Medially at the point of division, several chordae insert on the right (more common), top or left side of the crest of the ventricular septum Laterally, the superior bridging leaflet attaches to the anterior papillary muscle of each ventricle The non-divided posterior bridging leaflet attaches to the crest of the ventricular septum medially and to the posterior papillary muscles of each ventricle laterally The VSD is largest underneath the superior bridging leaflet The left superior bridging leaflet forms the floor of the already elongated LVOT, which looks especially narrow during atrial systole on the ventriculogram and echocardiogram, giving a characteristic “gooseneck” appearance This is the form of CAVC most frequently associated with LVOT obstruction (caused by chordal attachments to the LV side of the ventricular septum, subaortic membrane, septal hypertrophy or anomalous anterolateral papillary muscle) [1, 6] Rastelli Type B (Figure 10 and 11) This is the rarest type of complete CAVC (1-2%) The superior bridging leaflet is partially divided to the right of the plane of the ventricular septum and attaches to a papillary muscle of the right ventricle (straddling chords from the left component to the RV) but not to the ventricular septum The lateral insertion of the superior bridging leaflet and morphology of the inferior bridging leaflet is similar to the Rastelli type A The VSD is largest underneath the superior bridging leaflet [1, 6] Rastelli Type C (Figures 12 and 13, Videos 22 and 23) This is the second most common type of complete CAVC (25%) The superior bridging leaflet is undivided and unattached medially, or “free floating” over the crest of the septum The lateral insertion of the superior bridging leaflet and morphology of the inferior bridging leaflet is similar to Rastelli types A and B This form of CAVC is typically seen in association with conotruncal malformations (TOF, D-TGA) [1, 6] Canal type VSD This form of CAVC is characterized by a large inlet VSD with no primum ASD As in the other forms of CAVC, the common AV valve is divided into left and right components that share a common hinge point There is a cleft in the AML Also can exist without a common AVV but is frequently associated with complex congenital heart disease Balanced This term refers to the development of volume and mass of the ventricles When the ventricles are well developed the ventricular septum aligns with the middle of the common AVV, the common AVV opens approximately equally into both the morphologically right and left ventricles, and the ventricular inflow is equally distributed The echocardiographic definition of balanced CAVC is a modified AVV index (left component AVV area/total AVV area)= 0.5 [7] Unbalanced When the development of the ventricles is unbalanced, the ventricular septum does not align with the middle of the common AVV Instead it deviates towards one of its sides, and the common AVV opens preferentially into the ventricle that receives more inflow while the other is hypoplastic Unbalanced CAVC is frequently associated with heterotaxy syndromes, particularly when there is bilateral right-sidedness (asplenia syndrome or right atrial isomerism) Right ventricular type (right dominant, Videos 27, 28, 29) The common AVV opens predominantly or entirely into the morphologically right ventricle, while the morphologically left ventricle is hypoplastic This is frequently associated with left sided obstructive lesions A modified AVV index (left component AVV area/total AVV area) 0.6 is used as the cut off to define a left dominant canal by transthoracic echocardiography [7] Some authors utilize the term “atrial balance,” which refers to the position of the atrial septum in relation to the common AVV This classification has less clinical significance The atrial septum can be aligned with the middle of the common AVV or displaced towards one of its sides, in which case the bigger atrium empties into both ventricles and is described as a “double outlet atrium” Associated Cardiac Anomalies Common atrioventricular canal has been reported in association with almost all other minor or major congenital cardiac anomalies [5] Patent foramen ovale (PFO) Ostium secundum ASD Patent ductus arteriosus (PDA) VSD (typically muscular VSD, single or multiple) 13 Hahn, R.T., et al., Guidelines for performing a comprehensive transesophageal echocardiographic examination: recommendations from the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists J Am Soc Echocardiogr, 2013 26(9): p 921-64 14 Simpson, J., et al., Three-dimensional Echocardiography in Congenital Heart Disease: An Expert Consensus Document from the European Association of Cardiovascular Imaging and the American Society of Echocardiography J Am Soc Echocardiogr, 2017 30(1): p 1-27 15 Yang, S., et al., Evaluation of Ventricular Septal Defect Repair Using Intraoperative Transesophageal Echocardiography: Frequency and Significance of Residual Defects in Infants and Children Echocardiography, 2000 17(7): p 681-684 16 Lee, H., et al., Usefulness of Intraoperative Transesophageal Echocardiography in Predicting the Degree of Mitral Regurgitation Secondary to Atrioventricular Defect in Children Am J Cardiol, 1999 83: p 750-753 17 Kim, H.K., et al., Predictive value of intraoperative transesophageal echocardiography in complete atrioventricular septal defect Ann Thorac Surg, 2005 80(1): p 56-9 Figure Structures derived from the endocardial cushions (in gray) include the atrioventricular septum and septal aspect of the tricuspid and mitral valves Note the normal, more apical implantation of the septal leaflet of the tricuspid valve compared to the anterior mitral leaflet of the mitral valve Figure Normal anatomy of the heart’s base Showing 1) two atrioventricular connections formed by the mitral valve and tricuspid valve annuli, 2) central fibrous body formed by the right trigone and the membranous septum, 3) mitro-aortic relationship defined as fibrous continuity between the anterior mitral leaflet (AML) of the MV and the left (LCC) and non-coronary cusps (NNC) of the aortic valve, and 4) “wedged” position of the aortic valve between the mitral and tricuspid valve Figure Common atrioventriculuar valve (AVV) with left and right components (mitral y tricuspid valves in the normal heart) The abnormal division of the septal aspect of both components, or zones of apposition between the superior and inferior bridging leaflets are referred as “clefts” The common AVV is also characterized by a single annulus and a single or double AV orifice/s Additionally, there is absence of the membranous septum of the central fibrous body and superior and anterior displacement or “unwedging” of the aortic valve annulus by the common AVV This explains the abnormally elongated left ventricular outflow tract (LVOT) responsible for the typical radiologic, “gooseneck deformity” Figure Superior and anterior displacement of the aortic valve annulus by the common AVV and elongation of the left ventricular outflow tract (LVOT) Note that the outlet dimension is longer than the inlet dimension as apposed to the normal heart, where the two are more or less equal Figure Partial form of CAVC There is an interatrial communication in the canal portion of the atrial septum (ostium primum ASD) but no interventricular communication Although the canal portion of the ventricular septum is deficient, the potential VSD is completely closed by a “tongue” of valvular tissue and chords attached to the crest of the ventricular septum Note the abnormal septal implantation, or “common hinge point,” of the common AVV as compared to the normal heart in Figure Figure Partial form of CAVC A single AV junction and a common AVV with two AV orifices are present The superior and inferior bridging leaflets are fused above the crest of the ventricular septum to create a two-orifice common AVV (still with a single annulus/AV connection) “Clefts” in the left and right components of the common AVV are also present Figure Transitional form of CAVC An interatrial communication in the canal portion of the atrial septum (ostium primum ASD) and a pressure restrictive interventricular communication in the canal portion of the ventricular septum (inlet VSD) are present Interventricular shunting is restricted due to the presence of dense chord attachments from the superior and inferior bridging leaflets to the crest of the ventricular septum Figure Complete form of CAVC Rastelli type A An interatrial communication in the canal portion of the atrial septum (ostium primum ASD) and a large nonrestrictive interventricular communication in the canal portion of the ventricular septum (inlet VSD) are present The superior bridging leaflet is completely divided above the ventricular septum with chords typically attached to the right side of the crest of the ventricular septum Note the relatively normal size of the moderator band and location of the right anterior papillary muscle Figure Complete form of CAVC Rastelli type A A single AV junction and a common AVV with a single AV orifice are present The superior bridging leaflet is completely divided from edge to base (annulus) Multiple chords insert from each side of the divided superior bridging leaflet, typically to the right side of the crest of the ventricular septum Figure 10 Complete form of CAVC Rastelli B An interatrial communication in the canal portion of the atrial septum (ostium primum ASD) and a large nonrestrictive interventricular communication in the canal portion of the ventricular septum (inlet VSD) are present The superior bridging leaflet is partially divided above and to the right of the ventricular septum, with chords typically attached to the right anterior papillary muscle Note the smaller size of the moderator band and medial displacement of the anterior papillary muscle Figure 11 Complete form of CAVC Rastelli type B A single AV junction and a common AVV with a single AV orifice are present The superior bridging leaflet is partially divided above and to the right of the ventricular septum Multiple chords insert from each side of the partially divided superior bridging leaflet to the right anterior papillary muscle, which is medially displaced Figure 12 Complete form of CAVC type Rastelli C An interatrial communication in the canal portion of the atrial septum (ostium primum ASD) and a large nonrestrictive interventricular communication in the canal portion of the ventricular septum (inlet VSD) are present In the center, the superior bridging leaflet is undivided and unattached (“free floating”) Laterally, the superior bridging leaflet attaches to the anterior papillary muscle of each ventricle Note the relatively normal size of the moderator band and location of the right anterior papillary muscle This form is typical in Tetralogy of Fallot associated with CAVC Figure 13 Complete CAVC type Rastelli C A single AV junction and a common AVV with a single AV orifice are present In the center, the superior bridging leaflet is undivided and unattached (“free floating”) Laterally, the superior bridging leaflet attaches to the anterior papillary muscle of each ventricle This form of complete CAVC is typical in Tetrallogy of Fallot associated with CAVC Copyright © 2020 Congenital Cardiac Anesthesia Society 2209 Dickens Rd • Richmond, VA 23230-2005 View Privacy Policy E-mail: ccas@societyhq.com 804-282-9780 Built and Maintained by Ruggles Service Corporation ... nburbano-vera@partners.org James A DiNardo, M.D.,FAAP Professor of Anaesthesia Harvard Medical School Chief, Division of Cardiac Anesthesia Francis X McGowan, Jr., M.D Chair in Cardiac Anesthesia... position of atrial septum in relationship to the common AVV and ventricular septum, size of ASD, direction of the shunt and additional atrial septal defects AV canal Anatomy and function of the common. .. classify them? Journal of the American College of Cardiology, 1989 14(5): p 129 8-1 299 Cohen, M.S., Common Atrioventricular Canal Defects, in Echocardiography in Pediatric and Congenital Heart Disease,