Atrioventricular Septal Defect

Atrioventricular Septal Defect Dr Ranjith MP Senior Resident Department of Cardiology Government Medical college Kozhikode

Definition • Atrioventricular Septal Defects are characterized by complete absence of AV septum • Additional features • A common atrioventricular ring • A five leaflet valve that guards the common AV orifice • An unwedged left ventricular outflow tract • LV mass characterized by longer distance from apex to aortic valve than from apex to left AV valve • Also known as Endocardial cushion defect, AV canal defect, canalisatrioventriculariscommunis, persistent atrioventricular ostium

Incidence • AVSDs account for 4% to 5% of congenital heart disease • New England Regional Infant Cardiac Program - 0.118/1000 livebirths • Baltimore–Washington Infant study defined a prevalence of 0.362 • The Alberta Heritage study the prevalence was 0.203 and 0.242 per 1000 live births using invasive or noninvasive methodology for the diagnosis respectively • Gender distribution is approximately equal or may show a slight female preponderance

Historical note • Rogers, Edwards : Recognised morphology of 10ASD in 1948 • Wakai, Edwards : Term of partial and complete AV canal defect in 1956 • Bharati & Lev : Term of Intermediate & Transitional in 1980 • Rastelli: Described the of common anterior leaflet in 1966 • Lillehei : 1st repair of AVSD in 1954 • Kirklin, Watkin, Gross: Open repair using oxygenator

Embryogenesis • Result from Faulty development of the endocardial cushions and of the atrioventricular septum • In partial AVSDs, incomplete fusion of the superior and inferior endocardial cushions results in a cleft in the midportion of the AML , often associated with MR • Complete AVSD associated with lack of fusion between the superior and inferior cushions

Embryogenesis • Mitral & tricuspid valves achieve the same septal insertion level because the mitral annulus is displaced toward the apex • The distance from mitral annulus to the left ventricular apex is less than the distance from the aortic annulus to the apex

Embryogenesis • In the normal heart, the aortic valve is wedged between the mitral and tricuspid annuli. In AVSD the aortic valve is displaced anteriorly and creates an elongated, so-called gooseneck deformity of the LVOT

Morphoogy

Anatomical Classification of AVSD(Rastelli”s, 1996) • Based on the relationships of the anterior bridging leaflets to the crest of the ventricular septum or RV papillary muscles • Rastelli type A : the anterior bridging leaflet is tightly tethered to the crest of the IVS, occurring in 50% to 70% • Rastelli type B : (3%), the anterior bridging leaflet is not attached to the IVS; rather, it is attached to an anomalous RV papillary muscle and is almost always associated with unbalanced AV canal with right dominance • Rastelli type C : (30%) a free-floating anterior leaflet is attached to the anterior papillary muscle.

Relation Between the Associated Anomalies andRastelli Classification Kiyoshi suzuki et al J Am CollCardiol 1998;31:217–23

Associated anomalies • Partial AVSD • Most common 20 ASD & LSVC to CS • Less frequently- PS, TS or atresia, cortriatriatum, CoA, PDA, membranous VSD, PV anomalies, and HLV • Complete AVSD • Type A usually is an isolated defect and is frequent in patients with Down syndrome. • Type C – TOF, DORV, TGA and heterotaxy syndromes • The combination of type C complete AVSD with TOF is observed Down's syndrome, whereas DORV is a feature of patients with asplenia

Clinical characteristics of genetic disorders associated with AVSD M. Cristina Digilio et alCardiogenetics 2011; 1:e7

Hemodynamic changes • Anatomy of AVSD expected to demonstrate one or more of the following hemodynamic changes • Shunting across the atrial septal defect • Shunting through the ventricular septal defect • Mitral regurgitation • Tricuspid regurgitation • Patterns of shunting: obligatory shunting

Hemodynamic changes Fetal physiology • Greater proportion of SVC blood with a low oxygen saturation may cross the IAS to the LA • If AV insufficiency were present blood being ejected from LV to RA • Increase the PO2 of blood in RA, RV, PA • Slightly higher PO2 of blood perfusing the lungs would decrease pulmonary vasoconstriction and increase pulmonary blood flow • It is possible that the lesser degree of constriction of the pulmonary arterioles may retard the development of a thick medial muscle layer, so that a more rapid decrease in PVR may occur after birth

Hemodynamic changes Early infancy • Infants with ostium 10 defect usually present the same hemodynamic features as those with 20 ASD • As PVR falls after birth, RV after load falls & RV stroke volume increases and exceeds that of the LV. The RV fills preferentially and thus left-to right shunting occurs through the ASD • MR and LV to RA shunting are not usually prominent features in infants with 10 defect • If MR present, in early infancy cardiac failure develops within weeks after birth

Hemodynamic changes later infancy • Pulmonary blood flow is increased even though PVR may still be high, because shunting occurs from a high-pressure to a low-pressure chamber • The increased pulmonary blood flow and PA pressure interfere with the normal postnatal maturation of the pulmonary arterioles • The thick medial muscle layer is maintained and the fall in PR is delayed • An interesting association may develop in some infants of an obligatory left-to-right shunt through the atrioventricular septal defect and simultaneous right-to-left shunting through the ductus arteriosus • Pulmonary vascular resistance may be increased above systemic arterial resistance

Clinical manifestations • Partial AVSD • Patients with 10 ASD are usually asymptomatic during childhood. • Dyspnea, easy fatigability, recurrent RTI and growth retardation may be present early in life if associated with major MR or common atrium • Patients with 10 ASD usually have earlier and more severe symptoms than patients with 20 ASD • Complete AVSD • Tachypnea and failure to thrive invariably occur early in infancy & virtually all patients have symptoms by 1 year of age. • If these symptoms do not develop early on, the clinician should suspect premature development of pulmonary vascular obstructive disease

Physical examination • Usually undernourished and have signs of CHF • Hyperactive precordium with a systolic thrill at the lower left sternal border is common • S1 is accentuated. S2 narrowly splits, P2 increases in intensity. • A grade 3 to 4/6 holosystolic murmur

ECG & X-ray • ECG • Superior” QRS axis with the QRS axis between -40 and -1500 • Most of the patients have a prolonged PR interval • More than 50% have atrial enlargement • RVH or RBBB is present in all cases (2/3rd have rsR, RSR or Rr in lead V1, and the rest have a qR or R pattern) & many have LVH • Chest X-ray • In 10 ASD findings are same as 20 ASD except for enlargement of the LA & LV when MR is significant • In complete AVSD cardiomegaly is always present and involves all four cardiac chambers. Pulmonary vascular markings are increased, and the main PA segment is prominent

Echocardiography • Primary imaging technique for diagnosing AVSD • The internal cardiac crux is the most consistent imaging landmark • Apical four-chamber imaging plane clearly visualizes the internal crux • The 10 ASD is seen as an absence of the lower IAS

Echocardiography • Several echocardiac features are shared by all forms of AVSD: • Deficiency of a portion of the inlet ventricular septum • Inferior displacement of the AV valves • Attachment of a portion of the left AV valve to the septum • The two separate AV valve orifices are equidistant from the cardiac apex

Echocardiography • The most common left AV valve abnormality, a cleft, is best visualized from the parasternal and subcostal short-axis imaging planes. • Rarely parachute mitral valve and double-orifice mitral valve also occur

Echocardiography • In the transitional form of partial AVSD, there is aneurysmal replacement of a portion of the inlet ventricular septum

Echocardiography-1

Echocardiography-2

Cardiac Catheterization & Angiography • Rarely required for diagnosis • In older patient it may have a role in assessing the degree of pulmonary vascular obstructive disease or CAD • A large Lt to Rt shunt at the atrial level demonstrated by a significantly higher oxygen saturation sampled from the RA compared with the blood in the IVC & SVC • In complete AVSD the PASP is invariably at or near systemic level, while in partial AVSDs, the PASP is usually <60% of systemic pressure • LV angiography - gooseneck deformation of the LVOT

Cardiac Catheterization & Angiography Oxygen saturation data • Left to-right shunting increases the oxygen saturation in RA • Sample from high in the SVC usually represents the best • mixed venous oxygen saturation (normal or 40 to 50%) • Usually a further increase in oxygen saturation in the RV • Pulmonary venous oxygen saturation is frequently reduced to 93–95% in older individuals with very large L to R shunts • LA & LV O2 saturation is often decreased to as low as 86–88%

Cardiac Catheterization & Angiography • The LV angiogram shows features characteristic of AVCD& are best revealed in the hepatoclavicular orientation • The LV outflow tract is elongated and appears narrow • A concavity of the medial border LV that extends along the outflow region to the aorta due to the abnormal attachment of the AML. If it attaches to the ventricular septum or right papillary muscle, LVOT obstruction may be evident • Detect AV valve regurgitation

Natural History • The outcome of live-born patients with AVSD depends on the • specific morphology of the defect • The size of the ventricular septal defect • Degree of ventricular hypoplasia • Degree of AV valve regurgitation • Presence or absence of LVOT obstruction • Presence or absence of coarctation of aorta • Associated syndromes (cardiac and noncardiac)

Natural History • Patients with the complete form of AVSD and large VSD not undergoing repair die in infancy with CHF & PAH • Those who survive without surgery into childhood usually develop pulmonary vascular obstruction and eventually die with Eisenmenger’s syndrome • Berger and his colleagues found that only 54% of patients born with a complete form of AVSD were alive at 6 months of age, 35% at 12 months, 15% at 24 months, and 4% at 5 years of age • This data would support surgical intervention in the first 3–6 months of age Berger TJ,et al Ann ThoracSurg 1979; 27: 104–11.

Natural History • Infants with 10 ASD presenting in infancy have a poor outcome, mainly because of the associated risk factors that bring these infants to early attention • Those with the partial form of AVSD and minimal left AV valve regurgitation seem to fare the best without surgery, although there is still likely considerable morbidity and mortality • According to Somerville, 50% die before 20 years of age and only 25% survive beyond 40 years of age • Atrial fibrillation in these patients was an important cause of late morbidity and mortality

AVSD and Down syndrome • The complete form of AVSD is the most frequent type of CHD associated with trisomy 21 • 70% of children with complete AVCD display this aneuploidy • Children with Down syndrome show a simple form of AVCD which is usually complete & rarely associated with additional cardiac anomalies (with the only notable exception of TOF)

AVSD and Down syndrome • Left-sided obstructive lesions are significantly rare in children with AVCD and Down syndrome compared to patients with AVCD without Down syndrome • Accordingly, some types of situs abnormalities such as l-loop of the ventricles, atresia of the AV valves and TGA are virtually absent in subjects with Down syndrome • Surgical correction of AVCD in individuals with Down syndrome results in lower mortality and morbidity rates, compared to the children without trisomy (12.6% Vs 17.8%)

AVSD and Down syndrome • Patients are at increased risk for the development of pulmonary vascular obstructive disease • These patients have a greater degree of elevation of pulmonary vascular resistance in the first year of life and more rapid progression to fixed pulmonary vascular obstruction than patients without Down syndrome • Chronic upper airway obstruction with macroglossia and an inherently small hypopharynx, hypotonia, the predisposition to chronic infection, an abnormal capillary bed morphology, and the suggestion of pulmonary hypoplasia can all adversely affect the pulmonary vascular bed • surgical correction should be carried out by 6 months

LV outflow obstruction in AVSD • Incidence • 1% in unoperated cases • Higher incidence in operated cases • 10% may require reoperation to relieve LVOT obstruction • more common in partial than in complete AVSD • Etiology • Attachments of SBL to ventricular septum • Extension of the anterolateral papillary muscle into LVOT • Discrete fibrous subaortic stenosis • Tissue from an aneurysm of the membranous septum bowing into the LVOT • Septal hypertrophy

LV outflow obstruction in AVSD Systolic (left) and diastolic (right) echocardiographics demonstrating LVOT obstruction in a 17-year-old who had repair of a partial AVSD at age 15 months

Surgical Treatment of AVSD Banding of the pulmonary artery • PA banding is now performed infrequently in infants with AVSD because the surgical risks of intracardiac repair are not significantly greater than the palliative procedure • Perioperative mortality is about 5% • It is reserved for those few patients in whom intracardiac repair is likely to be associated with a high risk like • Single papillary muscle • Severe left ventricular outflow obstruction • Unbalanced commitment of the AV valve to the ventricles

Surgical Treatment of Partial AVSD • Objectives - closure of the interatrial communication and restoration and preservation of left AV valve competence • These objectives can be accomplished by careful approximation of the edges of the valve cleft with interrupted nonabsorbable sutures • The repair is completed by closure of the interatrial communication (usually with an autologous pericardial patch), avoiding injury to the conduction tissue • This repair results in a two-leaflet valve • Alternatively, if the left AV valve is to be considered a trileaflet valve, with the cleft viewed as a commissure, surgical repair demands that this commissure be left unsutured and that various annuloplastic sutures be placed to promote coaptation of the three leaflets

Surgical Treatment of Partial AVSD A: Surgical exposure B: Closure of the mitral valve cleft C: Prosthetic patch closure of an 10 defect D: Repair completed

Surgical Treatment of complete AVSD • Surgical repair of complete forms of AVSD is indicated earlier in life than for the partial forms of AVSD • Repair should be done electively before 6 months of age & earlier repair should be considered for infants with failure to thrive • For the symptomatic infant, surgical options include palliative pulmonary artery banding and complete repair of the anomaly • In the modern era complete repair appears to be the procedure of choice

Atrioventricular Septal Defect