What is Atrioventricular Septal Defect?

Atrioventricular septal defect (AVSD), also known as ‘Atrioventricular canal defect,’ is a form of congenital heart disease. It is characterized by a problem with the structure and functioning of the heart due to abnormal development before birth. In this condition, a large hole develops between the upper filling chambers of the heart and the lower pumping chambers of the heart. There also exists only one valve between the atria and ventricles instead of the usual two.

Atrioventricular Septal Defect Causes

This abnormal condition results due to inadequate fusion of the superior and the inferior endocardial cushions with the mid portion of atrial septum along with the muscular part of the ventricular septum. The main defect begins from the cardiac section which develops from the ‘endocardial cushions’.

The ‘endocardial cushions’ separate the central sections of the heart located near the tricuspid and mitral valves that divide the atria and the ventricles. Individuals suffering from AVS defect suffer from deformation in these sections of the heart. This may be due to the occurrence of a hole in the ventricular septum, atrial septum or tricuspid valves. Due to these holes, blood may not flow normally between the chambers of the heart. Naturally, the heart has to work harder to transfer blood to the lungs and to the rest of the body.

Atrioventricular Septal Defect Types

Several classifications of this condition have been made. However, the following two are most recognized.

Picture 1 – Atrioventricular Septal Defect Photo

Partial AVSD

In this form, a defect occurs in the primum or inferior portion of the atrial septum which have no direct intraventricular connection. In this condition, the mitral and the tricuspid annuli are found to be apart. Another defect in patients suffering from ASVD is the combination of primum ASD and cleft of the anterior mitral valve leaflet.

Complete AVSD

In this type, there is a large defect that involves the ventricular septum and the atrial as well. The defect is present in the whole area where the upper and the lower chambers of the heart conjoin. A large hole is seen below the atria and the upper portion of the ventricles which is an abnormality of the valves that separate the atria from the ventricles. The seriousness of the malformation depends mainly on the attachments of the valve to the ventricles and also where the valve allows the blood to flow from the right atrium to the right ventricle and from left atrium to left ventricle. This increases the pressure on the lungs as the blood flow also increases through the ventricles and atrial components. This increase in flow causes leaking in the atrio-ventricular valve which makes the ventricles contract and the blood flows forwards to the body but also backwards to the atria. The congestion due to back pressure causes heart failure in children as well as in adults.

Unbalanced AVSD

In this type of AVSD, there is dominance by either the right or left ventricle. The extent of damage in the pulmonary vasculature and the ventricular function differs from individual to individual.

Atrioventricular Septal Defect Symptoms

The signs or symptoms of this condition which helps doctors to diagnose are:

• A heart murmur is the first sign that the doctor notices.
• A heart that has an increased size is the other symptom.
• An abnormal electrocardiogram.

Babies suffering from congestive heart defect will have fast and hard breathing. They will sweat frequently and get tired easily during feeding. Their growth is slow and some of them lose weight abnormally. These children have maximum amount of blood flowing through the pulmonary artery. The defect also reduces the chances of the pulmonary ventricular resistance to increase.

Atrioventricular Septal Defect Diagnosis

The medical exams for diagnosing AVSD include:

• An electrocardiogram test, which measures the electrical activity in the heart.
• Ultrasound of the heart, to measure the blood flow.
• Chest x-ray, which shows the image of an enlarged heart.
• MRI scan of the heart, which produces a distinct image of the heart with the help of powerful magnets.
• Catheterization of the heart, in which a thin tube is placed inside the heart to check the blood flow and take correct measurements of blood pressure and oxygen levels.
• Pre-natal diagnosis, which can be made by examining the uterus through fetal echocardiogram.

Atrioventricular Septal Defect Treatment

Doctors may prescribe medication before opting for surgery if a patient is very sick. The medicines will help provide strength before the operation. If the patient is a child, the doctor will suggest medications to help the functions of the heart and lungs that is under pressure. The medications are Diuretics, Digoxin (mild inotrope), and furomeside for overloaded heart and ACE inhibitors like captopril for afterload reduction.

Atrioventricular Septal Defect Surgery

Surgery is opted for to cover the holes between the heart chambers. It separates the common valve into distinct tricuspid and mitral valves. The timing of the operation can be determined by the severity of the condition of a child. Surgery should be performed when the baby is about 3 to 6 months of age. In babies having a complete AVSD, surgeries should be over in the first year itself before any further damage to the lungs. The preoperative necessities such as pediatric cardiac methods such as anesthesia and preparation for surgery are done both in the cases of complete and incomplete Atrioventricular septal defects. Regular screening of the cervical spine is recommended prior to intubation for individuals affected by Down Syndrome.

The surgery involves closing of the atrial and ventricular septal defects. The defects are covered with a patch made from either a piece of the membrane of the heart or a synthetic material. The patch remains there permanently and the lining of the heart grows over time. The left AV valve is restored once the defects are covered. Open surgical methods call for a heart lung machine and are carried out with a median sternotomy. The partial atrioventricular canal defect is operated with the repairing of the mitral valve so that it closes properly. If the repair is not feasible, the valve has to be replaced. Complete Atrioventricular canal defect involves separation of the single valve into two valves, one on the left side and the other on the right side of the septum which has been repaired. If the reconstruction is facing problems, then replacement of the heart valve will be considered as a necessity.

Patients after surgery have to continue follow up trips to the doctor depending on the severity of atrioventricular valve regurgitation and other abnormalities.  Most patients need to be placed in Intensive Care Unit for 2 to 4 days and 5 to 7 days in hospital, if the complete atrioventricular septal defect has been repaired. This is done to keep a check on the complications which could arise in the functioning of heart valves or heart muscle. If the PVR increases before the surgery, patients would require artificial ventilation for a long time as well as several medications to ensure that the heart functions properly after surgery.

Atrioventricular Septal Defect Complications

Complications after the surgery are not impossible. Some complications may not show up until a child turns into an adult. These include heart rhythm and a leaking mitral valve. Complications may also crop up if the opening in the mitral valve is too narrow. Other problems requiring attention include trouble in the electrical system of the heart and narrowing of the passage of blood from the left ventricle to aorta. The areas where specialized tissues give out impulses to make the heart are very close to the stitches where the ventricular patch is required to be placed. If this sensitive area gets disrupted, a pacemaker has to be placed.

The complications can be summarized as follows:

Picture 2 – Atrioventricular Septal Defect Image

• Eisenmenger Syndrome
• Incurable damage to the lungs
• Death
• High blood pressure buildup within the lungs
• Congestive heart failure

Atrioventricular Septal Defect Prognosis

The general time for recovery in the case of partial atrioventricular septal defect is quite short. Most patients are released within 1 to 2 days and go home in 4 to 5 days after surgery. As per reports, the rate of survival associated with the condition is 97 percent.