Atrial Septal Defect and Anomalous Pulmonary Venous Connection in Adults

Atrial Septal Defect (ASD) is one of the most commonly diagnosed congenital heart defects in adults. It is often discovered incidentally during routine physical exams or through cardiovascular evaluations performed for unrelated symptoms. In later stages, untreated ASD can lead to abnormally elevated pulmonary artery pressure. Chronic left-to-right shunting can cause cardiac enlargement and result in various types of arrhythmias, predominantly atrial in origin.

Associated Conditions and Pathophysiology

ASD may be accompanied by varying degrees of Anomalous Pulmonary Venous Connection (APVC). The pathophysiology of isolated APVC resembles that of ASD, although right-to-left shunting is typically absent. The presence of abnormal venous drainage can further complicate hemodynamics and must be carefully evaluated before treatment planning.

Diagnostic Evaluation and Treatment Recommendations

Patients showing signs of right ventricular volume overload are generally advised to undergo ASD closure. Closure is considered safe for patients without significant pulmonary hypertension as indicated by non-invasive tests like echocardiography. However, for those with signs of pulmonary hypertension on non-invasive imaging, a right heart catheterization is recommended to measure pulmonary vascular resistance and pressure.

When Closure is Feasible

For patients with pulmonary vascular resistance between 3–5 Wood Units (WU), closure should be considered if there is clear evidence of left-to-right shunting with a pulmonary-to-systemic flow ratio (Qp/Qs) greater than 1.5, which can be estimated using echocardiography. For those with resistance ≥5 WU, a trial of targeted pulmonary hypertension therapy may be initiated. If resistance drops below 5 WU and Qp/Qs remains above 1.5, a fenestrated closure (leaving a small 3–4 mm opening in the closure patch) may be considered.

When Closure is Not Recommended

Patients with Eisenmenger syndrome (characterized by cyanosis and clubbing), persistent pulmonary vascular resistance ≥5 WU after therapy, or hypoxemia during exercise are not candidates for ASD closure. These individuals typically require lifelong medical management rather than surgical intervention.

Procedure Options and Outcomes

When anatomical conditions allow, minimally invasive transcatheter closure without cardiopulmonary bypass is the preferred approach. Studies show similar success and mortality rates between surgical and catheter-based methods. However, transcatheter procedures are associated with fewer complications and shorter hospital stays, albeit with a slightly higher rate of reintervention.

Corrective surgery for isolated APVC carries a risk of venous thrombosis due to slow flow dynamics. Therefore, such procedures should be performed by specialists in congenital heart disease.

Special Considerations

For patients with impaired left ventricular function or preoperative evidence of mitral regurgitation (visible on echocardiogram), the decision to close the ASD should be made with caution. In patients with pulmonary vascular resistance <5 WU, ASD closure has been shown to be safe and is associated with reduced pulmonary pressure and symptom improvement. However, the degree of improvement diminishes as pulmonary pressure increases.

Patients with resistance ≥5 WU are less likely to benefit from ASD closure and may experience worse outcomes with complete occlusion. Those with documented atrial arrhythmias may benefit from concomitant radiofrequency ablation during the procedure. In elderly patients, the risks and benefits of intervention must be carefully balanced to determine the most appropriate treatment strategy.