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
[email protected]
[email protected]
 
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
[email protected]

1. 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.

2. 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, oval-shaped AV annulus dislodges the aortic valve annulus from its normal “wedged” position between the annuli of the TV and MV (Figures 2 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.

3. Van Praagh Classification of CAVC [1]

• Partial (Figures 5 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 7 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 3 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 anterior-inferior 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 2 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 8 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) <0.4 is used as the cut off to define a right dominant canal by transthoracic echocardiography [7].
  • Left ventricular type (left dominant, Videos 30, 31). The common AVV opens predominantly or entirely into the morphologically left ventricle, while the morphological right ventricle is hypoplastic. 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”.

4. 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)
• LVOT obstruction. This can be seen in any type of CAVC but is more frequent in the complete form Rastelli type A. Whenever LVOT obstruction is present, coarctation of the aorta needs to be ruled out. Interestingly, LVOT obstruction is almost never present in association with trisomy 21.
• Double orifice mitral valve (DOMV, Videos 24, 25, 26). When present, usually the second orifice is small, competent and located in the inferior bridging leaflet.
• Single left papillary muscle. Typically this is a sign of LV hypoplasia and is seen in the right ventricular type of unbalanced CAVC. Creation of a parachute MV may occur when the left cleft is closed surgically.
• Tetralogy of Fallot (TOF, Videos 39, 40, 44, 45). Repair of these two lesions represents a surgical challenge because any residual pulmonary regurgitation resulting from a transanular patch technique of repair is deleterious for the repaired right component of the AVV (tricuspid valve in the normal heart). Typically the inlet VSD extends to the conus and is very large.
• Double outlet right ventricle (DORV). Due to the non-committed nature of the VSD, this poses an even greater surgical challenge for repair than the association of CAVC with TOF.
• Transposition of the great arteries (TGA). When present, this requires an arterial switch operation (ASO) in addition to the CAVC repair.
• Heterotaxy syndrome, particularly of the type bilateral right sidedness (asplenia syndrome or right atrial isomerism).

5. Pathophysiology

The clinical course in CAVC depends mainly on the magnitude of atrial and ventricular shunting, AVV regurgitation, degree of ventricular unbalance and the presence of associated lesions [2, 8]. In complete CAVC, the magnitude of ventricular shunting depends primarily on pulmonary vascular resistance (PVR). As a result, neonates are typically asymptomatic but signs of heart failure become evident as PVR decreases around 6-8 weeks of life. If left unrepaired, pulmonary vascular disease, elevated PVR and pulmonary artery hypertension (PAH) typically develop within the first year of life or earlier in children with trisomy 21. In the transitional form of CAVC, the ventricular shunt depends on the degree of restriction by the leaflet tissue so these patients may be asymptomatic or develop heart failure. In partial CAVC, the atrial shunt depends mainly on ventricular compliance, therefore shunting increases over the first weeks of life as RV compliance increases but symptoms present later in life. Atrioventricular valve regurgitation usually originates in the left-sided cleft (mitral valve in the normal heart) and the central part of the right or left component of the common AVV. The presence of LVOT obstruction or coarctation of the aorta increases the amount of left to right shunting and accelerates the onset of clinical heart failure. Typically there is dilation of all four heart chambers, especially the RV and RA. It is important to distinguish RV dilation from an unbalanced right dominant CAVC. In cases of CAVC associated with RVOT obstruction, cyanosis may be the initial presentation. Airway obstruction due to compression of the left main bronchus by a severely dilated LA is not infrequent.

6. Preoperative echocardiographic evaluation

• Echocardiographic goals. As in any complete echocardiographic evaluation for congenital heart disease, a step-by-step segmental analysis should be performed for CAVC [9]. The most relevant preoperative information for the Cardiac Anesthesiologist in patients with CAVC includes:
  • Atria. RA and LA size, 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 AVV is vital.
    • Anatomy: number of AV orifices, number of leaflets, morphology of superior bridging leaflet, size of left mural leaflet, chordal attachments, Rastelli type, number of and spacing between left papillary muscles, presence of double orifice MV, presence of parachute MV.
    • Function: presence of AVV regurgitation, location and mechanism of regurgitation, presence of AVV stenosis.
  • Ventricles. RV and LV size and function, ventricular balance, size of VSD, direction of the shunt, VSD gradient, estimation of RV pressure, additional ventricular septal defects, presence of LVOT or RVOT obstruction, severity and mechanism of obstruction.
  • Conus (subpulmonary infundibulum). Presence of RVOT obstruction.
  • Great arteries. Presence of coarctation of the aorta.
• Transthoracic echocardiographic evaluation. Reviewing the transthoracic images prior to the surgical procedure is highly recommended as this is a great way to learn echocardiography and understand the anatomy of the patient. It also facilitates the performance of the more directed transesophageal intraoperative exam.
  • Subxiphoid (subcostal) views. Typically the exam begins with a “subxiphoid sweep” to determine the abdominal situs (position of the liver, IVC, and descending aorta) [9].
    • Long-axis (coronal or frontal, Video 32). The probe is placed immediately underneath the xiphoid process at approximately a 30° angle with the skin, with the notch at the 3 o’clock position. This is the best view to assess the ostium primum type ASD, additional ASDs, and “gooseneck deformity”. It is also useful to assess the relationship of the common AVV to the septum, and unwedging of the aortic valve [10].
    • Left Anterior Oblique (“in-between”). The probe is rotated 30-45° from the Subxiphoid Long-Axis view with the notch at the 4-5 o’clock position. Best view to show the common AVV “en face”.  All the information obtained with the previous view can also be acquired from this location. An AVV index (left component AVV area/right component AVV area) <0.67 obtained from this view is considered a risk factor for biventricular repair in right dominant CAVC [11].
    • Short-axis (sagittal, Videos 13 and 14). The probe is rotated clockwise about 90° from the subcostal long-axis view with the notch at the 6 o’clock position. This is the best view for anatomy of the common AVV, chordal attachments, and Rastelli classification. Also useful in assessing the location and spacing of papillary muscles (muscle location changed from the normal 2 and 7 o’clock position to the 12 and 6 o’clock position).
  • Apical views [9]
    • Four-Chamber (Videos 9, 10, 13, 14, 20, 22, 24, 25, 27, 28, 30, 31). The probe is positioned at the apical impulse point with the notch at the 2-3 o’clock position. This is the best view for AVV inflow and regurgitation (Videos 10, 14, 25, 28, 31). The LV inflow index (LV inflow with color flow Doppler at the level of papillary muscles/2D left AVV annulus diameter) is measured from this view using 2D imaging and color flow Doppler. A LV inflow index <0.55 favors single ventricle palliation over biventricular repair in right dominant CAVC [12]. It is also useful for orientation of the AVV within the ventricular mass, size of ASD and VSD, additional VSDs, chordal attachments to the ventricular septum, and atrial and ventricular balance. The atrial septum should not be assessed with 2D echocardiography from this location (frequent drop out resulting from parallel alignment of the ultrasound beam with the atrial septum. Recall the basics: good 2D imaging with 90° angle of interrogation vs. good Doppler analysis with 0° angle of interrogation). A LV and RV cavity ratio (LV length x LV width/RV length x RV width) <0.46 obtained from this view is considered a risk factor for biventricular repair in right dominant CAVC [11].
    • Five-Chamber (Video 21 and 32). The probe is kept the same position as the 4-Chamber view but is angulated anteriorly (drop the tail of the transducer). This is the best view for LVOT obstruction identification (color flow Doppler) and severity classification (pulsed-wave and continuous-wave Doppler). Abnormal elongation and narrowing of the LVOT is also evident from this window.
  • Parasternal views [9]
    • Long-axis (Videos 34 and 35). The probe is placed on the upper left sternal border with the notch at the 10 o’clock position (towards the right shoulder of the patient). The standard Parasternal Long-Axis view shows the left side of the common AVV and the Right Ventricular Inflow view shows the right side. Since the alignment between the ultrasound beam and the AVV regurgitant jet is variable depending on the location of the jet (medial jets are parallel and lateral jets more perpendicular), the Parasternal Long-Axis view is not always adequate for measurement of the vena contracta in the left side of the valve. This window is also useful for distinguishing between atrial and ventricular shunting, and screening for LVOT obstruction with color flow Doppler.
    • Short-axis (Video 36 and 37). The probe is rotated about 60-90° from the parasternal Long-Axis view with the notch at the 2 o’clock position (towards the left shoulder of the patient). Along with the Subxiphoid Short-Axis, this is the best view for “clefts” and papillary muscle orientation. This window is also useful for visualization of VSD, additional muscular VSDs, and of the superior and inferior bridging leaflets.
  • Suprasternal Notch view [9]
    • Long-Axis. The probe is placed on the suprasternal notch with the transducer’s marker at the 1-2 o’clock position. This window is useful  for evaluation of the aortic isthmus.

7. Intraoperative echocardiographic evaluation

• Echocardiographic goals prebypass. Most information should have been obtained preoperatively with transthoracic echocardiography and additional imaging modalities when clinically indicated. Therefore the prebypass transesophageal echocardiographic exam should be focused on these very specific points: confirming the diagnosis, AVV morphology, and etiology of AVV regurgitation.
• Prebypass transesophageal echocardiographic evaluation. Although most intraoperative exams are performed with transesophageal echocardiography, epicardial echocardiography should be used when TEE is contraindicated (Video 29).
  • Midesophageal Views
    • Four-Chamber (Videos 2, 3, 6, 11, 12, 14, 21, 23, 25). This is perhaps the single most important view in TEE for analysis of CAVC since virtually all the components of the disease can be assessed from this position. It is the equivalent of the Apical Four-Chamber View of the transthoracic exam and from it similar information can be obtained. Due to the dilation of the heart, mainly the RV, the multiplane array may have to be rotated up to 20-40° to maximize the RV cavity and obtain a real 4-Chamber view. Turning the probe to the right positions the atrial septum in a more perpendicular position compared with the ultrasound beam and improves its visualization and Doppler analysis. Due to the perpendicular alignment of the common AVV in the closed position with the ultrasound beam, it provides a great opportunity for 2D and 3D anatomic analysis of the valve (Video 4) [13]. As in the normal study of the MV from this window, the totality of the common AVV can be examined in the vertical plane (from superior bridging leaflet to inferior bridging leaflet or vice versa) by simply advancing and withdrawing the probe. Clefts are easily observed or at least suspected from this position as a “disappearance” of valvular tissue during the opening or closing of the valve, especially when color compare is used. When AVV regurgitation is present, mainly in the left side of the valve, almost parallel alignment is achieved between the regurgitant jet and the ultrasound beam. When examining a regurgitant lesion from this level, special attention should be paid to ensure that all three components of the jet (proximal isovelocity surface area or PISA, vena contracta and expansion of the jet) have been acquired within the same image plane (Video 3, 6, 12, 14). This is the only way in 2D echocardiography to be certain the ultrasound beam is well aligned with the regurgitant jet and its real origin has been identified. This process is much easier with 3D echocardiography with the use of multiplanar reconstruction (MPR, Video 38) [14]. The pattern of ventricular inflow and measurement of AVV gradients is also optimally imaged from the 4-Chamber view. The size of the VSD and direction of the shunt, as well as atrial and ventricular balance, are readily inspected from this view.
    • Five-Chamber (Video 21). This view allows a good initial screening for LVOT obstruction with color flow Doppler, although ultrasound alignment typically is suboptimal for pulsed-wave and continuous wave Doppler. This plane usually images the LVOT in the lateral dimension.
    • Long-Axis (Video 7 and 19). Similar to the 5-Chamber view, this is useful for recognition of LVOT obstruction with color flow Doppler but suboptimal for pulsed-wave and continuous wave Doppler. It images the LVOT in a more anterior-posterior dimension. The characteristic “gooseneck deformity” of the LVOT is evident from this window.
    • Aortic Valve Short-Axis and RV Inflow-Outflow (Videos 39 and 40). These are useful for analysis of the right component of the common AVV. Typically good alignment is obtained with a regurgitant jet at this level. These windows are also useful for assessment of the RVOT with 2D imaging and color flow Doppler but not pulsed-wave or continuous wave Doppler.
    • Bicaval. Best view for additional atrial septal defects, mainly of the type ostium secundum and patent foramen ovale (PFO).
  • Transgastric Views
    • Basal Short-Axis (Videos 5 and 8). This is the equivalent of the Parasternal Short-Axis MV and Subxiphoid Short-Axis MV Views, and similar information can be acquired from this view. The multiplane array may have to be rotated up to 20-30° in order to obtain an “en face” view of the common AVV. This is arguably one of the most useful views for anatomic analysis of the common AVV. When combined with color flow Doppler, the location of the jet/s of regurgitation can be readily identified. The Basal Short-Axis view is particularly useful for identification of clefts on the right or left side components of the common AVV.
    • Mid Papillary Short-Axis (Video 18). This is the equivalent of the Parasternal Short-Axis Mid Papillary and Subxiphoid Short-Axis Mid Papillary Views, and similar information can be obtained from it. Especially useful for assessment of ventricular size in the cross sectional plane, position of the ventricular septum, and additional VSDs (the totality of the muscular ventricular septum can be scanned with color flow Doppler by advancing/withdrawing or anteflexing/retroflexing).
    • Aortic Valve Short-Axis and RV Inflow-Outflow. These two views are very similar in terms of the anatomic and Doppler information they provide. Best view for Doppler analysis of the right side of the common AVV and the RVOT.
    • Two-Chamber. Although this view is not utilized very frequently by Pediatric Cardiologists, it is perhaps the best window for the anatomic study of the subvalvular apparatus of the common AVV. Medial and lateral chordal insertions can be easily identified from this location. Rightward rotation of the probe is needed for the assessment of the right side of the valve.
    • Long-Axis. This view may be challenging to obtain due to the “unwedging of the aortic valve” by the common AVV and is not used frequently by Pediatric Cardiologists. It provides a fair alignment with the LVOT for assessment of obstruction with pulsed and continuous wave Doppler.
    • Deep Transgastric Five-Chamber and Transgastric View of the LVOT (Video 48). Although the Deep Transgastric 5-Chamber View is considered the “Gold Standard” in TEE for velocity and gradient measurement of the LVOT and aortic valve, it is not used much by Pediatric Cardiologists. Instead, they typically interrogate the LVOT from the Mid Papillary Short-Axis location by anteflexing the probe until the LVOT comes into view. Good alignment with the LVOT and aortic valve is achieved with this maneuver as well. These two views are ideal for the analysis of LVOT obstruction with pulsed-wave and continuous-wave Doppler.
  • Upper Esophageal Views
    • Aortic Arch Long-Axis. The main utility of this view is the 2D and Doppler analysis of the aortic isthmus in cases of coarctation of the aorta.
• Echocardiographic goals postbypass. In contrast to the prebypass exam, the postbypass examination should be very detailed with comprehensive assessment of the adequacy of the repair and detection of new abnormalities. Potential issues include residual ASD, VSD, AVV regurgitation or stenosis, ventricular dysfunction and LVOT obstruction. Residual ASD is unusual due to the easy surgical exposure and access to the atrial septum from the RA incision. Residual VSD is more common and the treatment depends mainly on the size of the defect (the number to remember is 3 mm). Ventricular septal defects ≤3 mm at its greater diameter do not require intervention but VSDs ≥4 mm typically require a second bypass run [15]. Left AVV regurgitation is more common than right and typically occurs at the interface of the superior and inferior bridging leaflets. Although multiple methods for assessment have been studied most practitioners use regurgitant jet area/LA jet area. The severity of AVV regurgitation assessed with transesophageal echocardiography in the operating room does not correlate well with the follow up postoperative transthoracic exam assessment [16, 17]. Risk factors for AVV stenosis include complete closure of the “cleft”, small left component of superior bridging leaflet, single left papillary muscle, absence of a left mural leaflet, and uneven distribution of the superior bridging leaflet during surgical repair.
• Postbypass transesophageal echocardiographic evaluation.
  • Midesophageal Views
    • Four-Chamber (Videos 41, 42, 43). Best view for assessment of residual AVV regurgitation and presence of new stenosis following repair. This view is also useful for assessing biventricular function and residual ASD and VSD.
    • Five-Chamber (Video 21). Useful for LVOT assessment with 2D imaging and color flow Doppler.
    • Long-Axis (Videos 7 and 19). Same as the Five-Chamber view.
    • Aortic Valve Short-Axis and RV Inflow-Outflow (Videos 44, 45). Compliments the Four-Chamber view in assessing residual regurgitation and new stenosis of the right side of the common AVV.
  • Transgastric Views
    • Basal Short-Axis (Videos 5 and 8). Best view for anatomic analysis of the common AVV before and after the repair as it facilitates clear localization of residual regurgitant jets.
    • Mid Papillary Short-Axis (Videos 18 and 46. Useful for assessment of biventricular function, ventricular septal position, preload status and residual muscular VSDs.
    • Right Ventricle Basal and Right Ventricle Inflow-Outflow (Videos 47 and 48). Not used very frequently by adult cardiac echocardiographers but favored by pediatric cardiologists since they resemble the Subxiphoid Short-Axis Views. Useful for assessment of the right component of the common AVV (Inflow-Outflow only) and RVOT (Basal and Inflow-Outflow).
    • Deep Transgastric Five-Chamber and Transgastric view of the LVOT . Gold standard for Doppler assessment of the LVOT.

1. Van Praagh, R.L., S. , Pathology and Embriology of common atrioventricular canal. Progress in Pediatric Cardiiology, 1999(10): p. 115-127.
2. Ebels, T., N. Elzenga, and R.H. Anderson, Atrioventricular Septal Defects, in Paediatric Cardiology, R.B. Anderson, EJ; Redington, A; Rigby, ML; Penny, DJ., Editor. 2010, Churchill Livingstone: Philadelphia. p. 553-589.
3. de Vlaming, A., et al., Atrioventricular valve development: new perspectives on an old theme. Differentiation, 2012. 84(1): p. 103-16.
4. Van Praagh, R., T. Geva, and J. Kreutzer, Ventricular septal defects: How shall we describe, name and classify them? Journal of the American College of Cardiology, 1989. 14(5): p. 1298-1299.
5. Cohen, M.S., Common Atrioventricular Canal Defects, in Echocardiography in Pediatric and Congenital Heart Disease, W.W. Lai, et al., Editors. 2016, Willey Blackwell. p. 259-278.
6. Rastelli, J., C.; Kirklin, J. W.; Titus, J. L., ANATOMIC OBSERVATIONS ON COMPLETE FORM OF PERSISTENT COMMON ATRIOVENTRICULAR CANAL WITH SPECIAL REFERENCE TO ATRIOVENTRICULAR VALVES. Mayo Clinic Procedures, 1966. 41: p. 296-308.
7. Jegatheeswaran, A., et al., Echocardiographic Definition and Surgical Decision-Making in Unbalanced Atrioventricular Septal Defect. Circulation, 2010(122): p. S209-S215.
8. Kaza, A.K., L.L. Minich, and L.Y. Tani, Atrioventricular Septal Defects, in Pediatric and Congenital Cardiology, Cardiac Surgery and Intensive Care, E.M.d. Cruz, Editor. 2014, Springer-Verlag: London. p. 1479-1491.
9. Lai, W.W., et al., Guidelines and standards for performance of a pediatric echocardiogram: a report from the Task Force of the Pediatric Council of the American Society of Echocardiography. J Am Soc Echocardiogr, 2006. 19(12): p. 1413-30.
10. Silvestry, F.E., et al., Guidelines for the Echocardiographic Assessment of Atrial Septal Defect and Patent Foramen Ovale: From the American Society of Echocardiography and Society for Cardiac Angiography and Interventions. J Am Soc Echocardiogr, 2015. 28(8): p. 910-58.
11. Cohen, M.S., et al., Morphometric Analysis of Unbalanced Common Atrioventricular Canal Using Two-Dimensional Echocardiography. Journal of the American College of Cardiology, 1996. 28(4): p. 1017-1023.
12. Szwast, A.L., et al., Usefulness of left ventricular inflow index to predict successful biventricular repair in right-dominant unbalanced atrioventricular canal. Am J Cardiol, 2011. 107(1): p. 103-9.
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.

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