Atrial Septal Defect
An atrial septal defect (ASD) is one of the most common forms of congenital heart disease found in adults. Although there are at least three different forms of atrial septal defect, they all have in common a communication between the right and left atrium. If the ASD is large enough, it produces enlargement of the right side of the heart, arrhythmias, and sometimes pulmonary hypertension. In some patients, an ASD is discovered incidentally. In others, it can be suspected because of an abnormal cardiac exam, palpitations, or shortness of breath. The diagnosis is generally confirmed with an echocardiogram. The three most common forms of ASD are: secundum, sinus venosus, and primum defects.
The secundum defect is the most common form of ASD and generally occurs as an isolated defect. It results from failure of a part of the atrial septum to close completely when the heart is developing. In the past, surgery was required to close a secundum ASD. However, following the approval of the ASD closure device in 2002, most secundum ASDs can be closed with a catheter.
The ASD closure device is inserted during a cardiac catheterization under echocardiographic guidance. Patients are discharged the following day on anti-platelet medications for six months. Unlike cardiac surgery, there is little or no recuperation following this procedure.
A primum ASD is a hole in the inferior and posterior portions of the atrial septum adjacent to the AV valves. It is also associated with a cleft in the mitral valve which may result in a leak, known as mitral regurgitation. Correction of this defect requires surgery and consists of patch closure of the ASD and repair of the mitral valve cleft. Surgical expertise in congenital heart disease is required to repair this defect because of its proximity to the electrical system of the heart and the mitral valve abnormality.
Sinus Venosus ASD
A sinus venosus ASD is located in the superior and posterior portion of the atrial septum. It is more difficult to visualize with echocardiography than the other forms of ASD which is a reason why there is often a delay in recognizing this defect. This form of ASD is associated with abnormal drainage of one or more right sided pulmonary veins. Surgical repair involves patch closure of the ASD and redirection of the abnormal pulmonary vein back to the left atrium.
There are other less common forms of congenital heart disease that can mimic the symptoms of an ASD. This includes anomalous drainage of one or more pulmonary veins and a coronary sinus ASD. In both of these abnormalities, symptoms are related to the excess blood flow into the right side of the heart. Surgical repair is recommended when there are signs and symptoms of a significant increase of blood flow into the right heart.
ASD closure eliminates the excess blood flow which produces enlargement of the right side of the heart. Pulmonary artery pressure may or may not be elevated in an adult with unrepaired ASD. Patients with mild or moderate degrees of pulmonary hypertension often experience improvement in pulmonary artery pressure following ASD closure but may also benefit from the use of advanced pulmonary vasodilator therapy. If pulmonary hypertension is severe, then ASD closure may not be advisable. Careful evaluation of such patients by experts in pulmonary hypertension is important.
ASD closure also eliminates the potential for paradoxical embolization, a situation in which a blood clot can enter the systemic circulation from the right side of the heart and produce a stroke or damage to other organs. While exercise capacity is improved in many patients after ASD closure, arrhythmias, if present, may persist when surgery is carried out in older patients.