Atrial septal defect (ASD) is the most common congenital heart disease in adults, accounting for 20%-30% of adult congenital heart diseases. The male-to-female ratio of incidence is 1:1.5-3, and there is a familial hereditary tendency.
Pathological Anatomy
ASD is generally classified into primum atrial septal defect and secundum atrial septal defect. The latter can be further divided into central type, inferior vena cava type, superior vena cava type, and mixed type, with the central type being the most common. Multiple defects may also coexist.
Pathophysiology
The hemodynamic impact of ASD primarily depends on the magnitude of the shunting. Persistent increased pulmonary blood flow leads to pulmonary congestion, increased right heart volume load, and decreased pulmonary vascular compliance. This can progress from functional pulmonary hypertension to organic pulmonary hypertension, and in late stages, Eisenmenger syndrome may develop.
Clinical Manifestations
ASD is typically asymptomatic. As the condition progresses, symptoms such as exertional dyspnea, arrhythmias, and right heart failure may appear. In late stages, approximately 15% of patients develop right-to-left shunting due to severe pulmonary hypertension, resulting in cyanosis and the development of Eisenmenger syndrome.
The most characteristic physical sign is an accentuated and fixed splitting of the second heart sound in the pulmonary valve area. In some patients, a grade II-III systolic murmur with a blowing quality may also be heard.
Auxiliary Examinations
Electrocardiography (ECG)
Findings may include right axis deviation, right ventricular hypertrophy, and right bundle branch block.
Chest X-ray
Chest x-ray may show right atrial and right ventricular enlargement, a prominent pulmonary artery segment, and increased pulmonary vascular markings.
Echocardiography
Echocardiography demonstrates a continuous interruption in the atrial septum.
Diagnosis and Differential Diagnosis
The combination of characteristic cardiac auscultation findings, ECG, and chest x-ray can suggest the presence of ASD. Echocardiography confirms the diagnosis. Differential diagnoses include anomalous pulmonary venous drainage, pulmonary valve stenosis, and small ventricular septal defects.
Treatment
For adult patients with ASD, closure should be performed as early as possible if echocardiographic evidence of right ventricular volume overload is present. Treatment options include interventional procedures and open surgical repair.
Before the advent of interventional procedures, all hemodynamically significant isolated ASDs were treated surgically.
Prognosis
The most common cause of death is heart failure, followed by pulmonary infections, pulmonary artery thrombosis, or embolism.