Fig. 17.1
Angiographic presentation of AVSD known as “goose neck deformity” before the start of systole
Fig. 17.2
Angiographic presentation of AVSD known as “goose neck deformity” in systole
Fig. 17.3
Angiographic presentation of AVSD known as “goose neck deformity” in early systole
Pathologic Findings and Associated Anomalies
The three main mechanisms described in the previous section lead to the pathologic findings seen in AVSD; all of them are the result of the main faulty developmental defect, i.e., endocardial cushion defect. The main pathologies found in patients with AVSD are the following (Craig 2006; Adachi et al. 2008):
- 1.
In normal hearts, each AV valve has a separate annular ring: one for the mitral valve and the other for the tricuspid valve. In hearts with AVSD, there exists only one common valve ring, i.e., just we could imagine that the AV junction failed to separate during fetal life, resulting in one common AV valve ring. This common annulus does not follow the normal figure of eight seen in normal AV valves; instead one ovale ring exits for connecting between atria and ventricles.
- 2.
Normal mitral and tricuspid leaflets are not seen anymore; instead, a special anatomic configuration exists in these leaflets often described under the Rastelli classification. The common AV valve typically, but not always, has 5-leaflet configuration with common AV valve annulus (i.e., complete AVSD). Occasionally, there are two AV valve annuli within the common AV valve junction if a piece of tissue “band” divides the common AV valve to two separate orifices (i.e., partial AVSD). The two orifices create separate right and left passages for blood. Despite having two AV valve annuli, however, these hearts still have a common AV valve junction, which is the fundamental feature of AVSD.
- 3.
The pathologic annulus (i.e., oval-shaped common AV valve junction) decreases the space needed for the LVOT and aorta to emerge from the left ventricle; so, there is an anterior deviation and tendency for the aorta and LVOT named as anterior scooping of the aorta; see Figs. 17.1, 17.2, and 17.3 (Adachi et al. 2009a, b).
- 4.
The anterior scooping of the aorta lengthens the course of blood movement from the LV through LVOT; in the normal hearts, the distance from the mitral valve till the LV apex (i.e., the LV inlet) is approximately equivalent to the distance from the LV apex to the aortic valve (i.e., LV outlet) causing the LV outlet/inlet ratio of 1/1. In AVSD, however, this ratio is increased due to anterior scooping of LVOT.
- 5.
Orientation of the papillary muscles is different in hearts with AVSD. For example, the papillary muscles of the left AV valve in AVSD have more or less superior–inferior orientation, while the papillary muscles of the normal mitral valve have oblique orientation.
- 6.
Defects in the interatrial septum with resultant shunting at the atrial level (ASD primum) are seen often in hearts with AVSD. There exist hearts with AVSD but not having primum ASD. This rare subset is called “AVSD with only ventricular component” (Adachi et al. 2009c). This rare form of AVSD is not often seen in clinical setting in part because this anatomy is considered as “AV canal-type VSD” or “inlet VSD.” However, it must be remembered that what differentiates hearts with AVSD from VSD is the presence of common AV valve junction. Regardless of the level of intracardiac shunting, the hearts should be categorized under the spectrum of AVSD if there is a common AV junction.
- 7.
Defects in the caudal and posterior section of the ventricular septum create shunting at the ventricular level as seen in intermediate and complete types of AVSD. As mentioned above, the ventricular-level defect is often called inlet-type VSD. However, care must be taken to use this terminology since “VSD” implies there is normal separation of the AV valve junctions.
- 8.
The common AV valve typically has 5-leaflet configuration:
Superior bridging leaflets, SBL (also named anterior bridging leaflet).
Inferior bridging leaflets, IBL (also named posterior bridging leaflet); both SBL and IBL cross over the interventricular septum; also, each of these two leaflets is attached to both the right ventricle and left ventricle through chordae tendineae, though the chordae and their anatomic arrangement are different from normal.
Right anterolateral leaflet.
Right mural leaflet.
Left mural leaflet.
Classification of AVSD
In general, hearts with AVSD are classified into three subtypes based on the level of intracardiac shunting (Jacobs et al. 2000; Craig 2006; Adachi et al. 2008, 2009c; Shuhaiber et al. 2009; Buratto et al. 2014; Xie et al. 2014):
Complete AVSD (both atrial- and ventricular-level shunting with a common AV valve). Complete AVSD is further subdivided to “Rastelli type A,” “Rastelli type B,” and “Rastelli type C” depending on the status of the superior bridging leaflet relative to the crest of the ventricular septum; detailed description of the Rastelli classification could be found in selected references.
Partial AVSD (the so-called ostium primum ASD plus cleft mitral valve) in which a tongue of tissue attaches the two SB leaflet and IB leaflet to create two separate orifices in the common AV valve; however, these two orifices are never true valves because they do not have real structure of separate and complete annulus, and their leaflets have minimal resemblance to the leaflets of the normal hearts.
AVSD with only ventricular component (typically described as AV canal–type VSD). This subtype of AVSD represents the mildest form of hearts with AVSD within the spectrum of AVSD. It is the least common form of the disease.
Associated Cardiac Anomalies
At times, AVSD is accompanied with some other cardiac malformations which complicate perioperative management and surgical procedure. The following cardiac anomalies may accompany AVSD (Craig 2006; Tchervenkov et al. 2006; Mitchell et al. 2007; Shuhaiber et al. 2009; Karl et al. 2010):
Tetralogy of Fallot (TOF) (which associated with complete AVSD and its combination results in RVOTO in AVSD)
Left ventricular outflow tract obstruction (congenital LVOTO) overlying AVCD
Subaortic stenosis
Double outlet right ventricle (DORV)
Truncus arteriosus (or common arterial trunk)
Common AV valve with single ventricle pathology
Ventricular hypoplasia
Left AV valve with double orifice
Unbalanced complete AVCD
Transposition of great arteries (TGA)
Atrial isomerism (left or right type of isomerism)
Clinical Presentation and Diagnosis of the Disease
The clinical findings in AVSD usually present with signs and symptoms of heart failure and failure to thrive, both of them with varying degrees. Also, cyanosis is usually either mild or absent. The findings related to pulmonary hypertension or pulmonary overflow like tachypnea and reduced activity may be seen.
ECG findings are the result of anatomic abnormalities in the interventricular septum (Fig. 17.4):
Fig. 17.4
Complete AVSD with left axis deviation, incomplete RBBB, and biventricular hypertrophy (Courtesy of Dr. Majid Haghjoo and Dr. Mohammad Rafie Khorgami)
P wave abnormalities including superior P wave axis are seen in patients with left atrial isomerism; superior axis deviation is considered as one of the most characteristic findings in AVSD patients.
AV node displacement from its normal position, leading to an enlarged bundle which paves its course alongside the ventricular septum.
Axis is deviated from −40 to −150.
Prolongation of the PR interval is due to intra-atrial conduction delay and may be seen in about 50 % of patients (first-degree AV block).
Right bundle branch block (RBBB) (usually partial block).
RVH pattern is always seen; however, LVH may be observed.
The most characteristic finding in AVSD is superior orientation of the frontal QRS wave, i.e., superiorly oriented counterclockwise QRS loop; this loop resembles “a figure-of-eight QRS loop” which lies on the upper part of the isoelectric line in the frontal plane; QRS is usually rSr´ or rsR´; also, QRS has moderate-to-severe left axis deviation (Feldt et al. 1970; Craig 2006; Khairy and Marelli 2007).
Echocardiography
Transthoracic echocardiography is the method of choice for preoperative diagnostic assessment. Intraoperative transesophageal echocardiography (TEE) provides even more detailed information necessary for surgical repair. These findings can be seen in intraoperative TEE (Craig 2006; Cohen and Stevenson 2007):
Right ventricular (RV) hypertrophy.
Right atrial (RA) hypertrophy.
ASD.
VSD: its severity depends on the subtype of disease.
Different degrees of tricuspid regurgitation (TR) which would depend on the structure of the right side of the AV valve and also the severity of pulmonary hypertension.
Pulmonary artery dilation especially when overflow of the pulmonary system is a marked finding.
Subvalvular aortic stenosis (due to the effects of mitral chordae and scooped aorta) though not a common finding could be seen in some patients and mandates sophisticated TEE assessments following surgical correction immediately after weaning from bypass.
Surgical Repair
A number of factors impact the outcome of surgical repair for AVSD, which includes the repair technique, underlying chromosomal abnormalities, severity of the disease and its subtypes seen in each patient, other associated cardiac anomalies, severity of regurgitation in common AV valve, age-matched z scores, and a number of other factors (Craig 2006; Halit et al. 2008; Karl et al. 2010; Ong et al. 2012).
The first successful repair of AVSD was performed in 1954 on a 17-month-old girl by Lillehei et al. Since then, various different approaches have been used for repair of AVSD (Wilcox et al. 1997; Nicholson et al. 1999; Backer et al. 2007; Nunn 2007; Halit et al. 2008; Shuhaiber et al. 2009; Jonas and Mora 2010):
- 1
Traditional single–patch technique which utilizes one patch for closure of both ASD and VSD. The AV valves are divided into the right and left components and sutured to the single patch through a right atriotomy.
- 2
Standard two–patch technique which uses two separate patches for ASD and VSD, usually the pericardium for ASD and one “pericardium, PTFE, or the Dacron patch” for VSD.
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