Atrioventricular septal defect

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Atrioventricular septal defect (AVSD), previously known as “common atrioventricular canal” (CAVC) or “endocardial cushion defect”, is a congenital heart defect characterized by the deficiency in development of the atrioventricular septum of the heart. It is caused by an abnormal fusion of the superior and inferior endocardial cushions with the mid-portion of the atrial septum and the muscular portion of the ventricular septum. The malformation results in a hole in the heart between the mitral and triscupid valves. This lack of separation can cause hemodynamic complications.

AVSD is classified as either complete, partial, or intermediate/transitional. Classification is based on the extent of loss of separation between the chambers of the heart. In partial AVSD, there is a defect in the primum or inferior part of the atrial septum but no direct intraventricular communication (ostium primum defect). In complete AVSD, there is a large ventricular component beneath either or both the superior or inferior bridging leaflets of the AV valve. In intermediate or transitional AVSD, the leaflets of the common AV valve are stuck to the ventricular septum causing a division of the two valves and resulting in a marginal sized hole between the ventricle. Transitional AVSDs are similar to partial AVSDs in behavior but visually appear more like a complete AVSD.

AVSDs can result in significant changes in hemodynamics. A defect in the septum can result in blood freely traveling from the left side of the heart to the right side of the heart resulting in mixing of oxygenated and deoxygenated blood. This mixed blood is pumped back to the lungs and causes an increase in blood volume in the lungs resulting in hypertension, cardiomegaly, and damage to the blood vessels. A high pulmonary pressure can result in a pulmonary edema

AVSDs account for approximately 5% of all congenital heart diseases. It is most commonly associated with patients with Down syndrome (trisomy 21) or heterotaxy syndromes.^[1] 45% of children with Down syndrome have some form of congenital heart disease. Of these, 35–40% have AV septal defects.^[2]

Most infants are largely asymptomatic and may only exhibit signs of failure to thrive. A clinical diagnosis often occurs based on the presence of a heart murmur and can be detected at any time, from fetal development to later in life. A fetal echocardiogram can detect the presence of a murmur during prenatal care. A cardiac catheterization can also used for diagnosis.

Surgical therapy is the most reliable method of treatment. An open heart surgery will separate the mitral and triscuspid valve and close the atrial and ventricular septal defects. Surgical therapy is not advised until a child is old enough to undergo surgery. A pulmonary artery banding surgery may be used to delay the necessity for surgery.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

AVSD is classified as either complete, partial, or intermediate/transitional. Classification is based on the extent of loss of separation between the chambers of the heart. In partial AVSD, there is a defect in the primum or inferior part of the atrial septum but no direct intraventricular communication (ostium primum defect). In complete AVSD, there is a large ventricular component beneath either or both the superior or inferior bridging leaflets of the AV valve. In intermediate or transitional AVSD, the leaflets of the common AV valve are stuck to the ventricular septum causing a division of the two valves and resulting in a marginal sized hole between the ventricle. Transitional AVSDs are similar to partial AVSDs in behavior but visually appear more like a complete AVSD.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

There are many underlying mechanisms resulting in atrioventricular septal defect depends largely on the nature of interaction of blood flow between the right and left sides of the heart. Factors influencing the severity include: ventricular imbalance, the size of AV septal defects, AVV competence, the degree of right-sided or left-sided outflow obstruction, pulmonary vascular resistance, the amount of atrioventricular valve regurgitation and the magnitude of blood flow through the ventricular septum. The determination of the degree of left-to-right shunting can be done examining the size of the communication and the relative compliance of the two atria and ventricles.

Newborns may experience little left-to-right shunting as a result of a less compliant right ventricle and a relatively high PVR. Larger defects may result in mixing of a common or near-common atrium and create components of right-to-left shunting. The propensity for left-to-right shunting increaes with age as a result of a decrease in PVR and right ventricle compliance increase.

Asymptomatic patients often have little atrioventricular valve regurgitation and higher pulmonary vascular resistance. Pulmonary overcirculation is often an earmark of an AVSD.

Infants may present with congestive heart failure, tachypnea, excessive sweating, failure to thrive, extremis with acidosis, severe hypoplasia of left-sided structures with ductal-dependent systemic circulation, and severe cyanosis in right-sided structures with ductal-dependent systemic circulation. If an AVSD is coupled with an VSD, there is a high risk of pulmonary vascular disease.

Older patients may present progressive right ventricle enlargement and pulmonary vascular engorgement.The degree of regurgitation through the anterior mitral valve leaflet cleft can result in a left ventricular outflow tract obstruction of a coarctation of the aorta.

{{#ev:youtube|4lOe4rRK5n0}}

Picture below shows atrial septal defect in atrioventricular septal defect

Picture below shows complete atrioventricular septal defect.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Atrioventricular septal defects (AVSDs) occur during gestational development of a fetus. The endocardial cushions are two areas of thickening that eventually develop into the wall (septum) that separates the four chambers of the heart. They also form the mitral and triscuspid valves, the valves that separate the atria from theventricles.

The lack of separation between the two sides of the heart causes several problems:

• Increased blood pressure in the lungs. In persons with this condition, blood flows through the abnormal openings from the left to the right side of the heart, then to the lungs. The increased blood flow into the lungs leads to a rise in blood pressure in the lungs.
• Lung irritation and inflammation. Increased blood flow into the lungs causes irritation and swelling.
• Heart failure. Because the heart has to pump more blood to the lungs, it has to work much harder than normal. The heart may enlarge and weaken.
• Cyanosis. As the blood pressure increases in the lungs, blood flow starts to move from the right side of the heart to the left. The oxygen-poor blood mixes with the oxygen-rich blood, and blood with less oxygen than usual is pumped out to the body.

AVSDs are strongly associated with Down syndrome. Several gene changes are also connected to ECD. However, the exact cause of ECD is unknown.

AVSDs may be associated with other congenital heart defects such as:

• Double outlet right ventricle
• Single ventricle
• Transposition of the great vessels
• Tetralogy of Fallot

de:Atrio-ventrikulärer Septumdefekt nn:Atrioventrikulær septumdefekt uk:Атріовентрикулярний септальний дефект

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

In the US, the prevalence of atrioventricular septal defects is between 3-5% in live births or about 0.19 per 1000 live births. The incidence of AVSD is higher in stillborn births, at a rate of approximately 7%. One explanation for this increase is this population’s propensity for chromosal and other anomalies. Of live births, approximately 45% of infants with Down syndrome and congenital heart disease have an atrioventricular canal defect. Atrioventricular septal defects are distributed about equal between males and females.^[1]

There is some evidence to suggest a potential link between atrioventricular septal defects and familial clustering. Approximately 14% of women with a common atrioventricular canal pass on the congenital heart disease to their children. In one analysis, 11.7% of children with atrioventricular septal defects had a family history of congenital heart disease^[2]

There is no epidemiological evidence to support any variation of incidence and prevalence based on race, sex or age. Onset is generally early in life, occurring within the first 6 weeks of life. In rare cases, patients can be asymptomatic during development and may experience a latent onset as cyanosis develops into a severe complication.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

The true natural history of an atrioventricular septal defect is difficult to definitively determine. No record exists to detail the course of disease of an untreated complete atrioventricular septal defect. In patients with a moderate case of a partial or incomplete atrioventricular septal defect, patients may be asymptomatic in the first decade of life. During adolescence, left-to-right shunting and atrial arrhythmia may present. As continued development occurs in these patients, sinus node dysfunction may develop and can lead to exercise intolerance. More severe cases of partial or incomplete atrioventricular septal defects left untreated can lead to morbidity in infancy and early childhood.

In general, long-term survival of patients with all types of atrioventricular septal defects had an overall poor prognosis. Mortality was higher in complex atrioventricular septal defect cases. Approximately 80% of patients with a complete AVSD died by age 2. Other studies have observed a trend between survival in the first year of life and complexity of defect. In one study, 54% of infants with a complete atrioventricular septal defect survived the first 6 months, 35% survived into one year of life, and only 4% survived 5 years of life.

There is no evidence to suggest that the association between atrioventricular septal defects and Down syndrome correlates to equally grim outcomes. One study documented only 4 late deaths over a 27-year period in patients greater than 1 year of age with un-operated defects.

Common complications from atrioventricular septal defect include:

• Congestive heart failure
• Pulmonary vascular obstructive disease/Eisenmenger syndrome
• Tachypnea
• Cyanosis
• Failure to thrive
• Sinus node dysfunction
• Hypertension in the lungs
• Irreversible damage to the lungs

When treated with surgical repair, patients with atrioventricular septal defect have a minimal long-term morbidity. Complete atrioventricular septal defect repair is 3.6% and the 10-year survival rate is 81%. Some patients may live the first few years of their life without surgical intervention. The surgical survival rate for pediatric complete atrioventricular septal defect is 94% with an overall survival rate of 91% of patients repaired between 4-6 months of age.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

AVSDs can be detected by cardiac auscultation, they cause atypical murmurs and loud heart tones. Confirmation of findings from cardiac auscultation can be obtained with a cardiac ultrasound (echocardiography) (less invasive) and cardiac catheterization (more invasive).

Tentative diagnosis can also be made in utero via fetal echocardiogram. An AVSD diagnosis made before birth is a marker for Down syndrome, although other signs and further testing are required before any definitive confirmation of either can be made.

de:Atrio-ventrikulärer Septumdefekt nn:Atrioventrikulær septumdefekt uk:Атріовентрикулярний септальний дефект

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