Sinus venosus atrial septal defect

Schematic drawing of various types of atrial septal defect

Sinus venosus atrial septal defect (SVASD) is a form of atrial septal defect (ASD), which is a congenital heart defect characterized by an abnormal opening in the atrial septum, the wall that divides the two upper chambers of the heart (the atria). Unlike the more common secundum atrial septal defects, sinus venosus defects are located near the junction of the superior vena cava (SVC) and the right atrium, either above (superior) or occasionally near the inferior vena cava (inferior SVASD).

Etiology and Pathophysiology

The development of SVASD is related to abnormal embryological development of the sinus venosus, an embryonic precursor to part of the right atrium and the venous return pathways including the SVC and the inferior vena cava (IVC). This defect results in a shunting of blood from the higher pressure left atrium to the lower pressure right atrium, leading to an increased volume of blood flow through the lungs. Over time, this can cause enlargement of the right atrium and right ventricle, increased pulmonary artery pressure, and may lead to heart failure and pulmonary hypertension.

Clinical Presentation

Patients with SVASD may be asymptomatic or present with symptoms related to the volume overload on the right side of the heart. Symptoms can include shortness of breath, especially during exertion, fatigue, palpitations, and in more severe cases, signs of heart failure such as swelling of the legs or abdomen. Physical examination may reveal a systolic murmur due to increased flow across the pulmonary valve.

Diagnosis

Diagnosis of SVASD involves imaging studies to visualize the defect and assess its effects on heart structure and function. Echocardiography is the primary diagnostic tool, often supplemented by cardiac MRI or CT for detailed anatomical assessment. These imaging studies can help differentiate SVASD from other types of ASD and evaluate for associated anomalies, such as anomalous pulmonary venous return.

Treatment

The treatment for SVASD typically involves surgical repair, especially in symptomatic patients or those with evidence of right heart enlargement or dysfunction. The goal of surgery is to close the defect and, if necessary, redirect anomalous pulmonary venous return to the left atrium. Surgical intervention is generally recommended to prevent long-term complications such as pulmonary hypertension and heart failure.

Prognosis

With timely and appropriate surgical intervention, the prognosis for individuals with SVASD is generally good. Most patients can expect a normal life expectancy and significant improvement in symptoms. However, long-term follow-up is necessary to monitor for potential complications, such as arrhythmias or pulmonary hypertension, even after successful repair.