Is Sinus Venosus ASD Rare?
No, sinus venosus ASD is not considered rare—it represents 5-10% of all atrial septal defects, making it the third most common type after secundum (75%) and primum (15-20%) defects. 1
Prevalence and Classification
Sinus venosus defects account for 5-10% of all ASDs, with the superior type (near the superior vena cava entry) being more common than the inferior type (near the inferior vena cava entry). 1, 2, 3
The inferior sinus venosus defect is genuinely rare, representing less than 1% of all ASDs, making it the rarest subtype of interatrial communications. 1
For context, secundum ASDs comprise 60-80% of cases, primum ASDs 15-20%, and coronary sinus defects less than 1%, placing sinus venosus defects firmly in the "uncommon but not rare" category. 1, 4, 2
Key Clinical Associations
Approximately 90% of sinus venosus ASDs are associated with partial anomalous pulmonary venous drainage (PAPVD), most commonly involving the right pulmonary veins draining into the superior vena cava or right atrium. 1, 2, 3
This association with PAPVD is critical because it increases the left-to-right shunt volume and accelerates the development of right ventricular volume overload and pulmonary hypertension. 5
Diagnostic Challenges
Sinus venosus defects are frequently missed on transthoracic echocardiography due to their superior or inferior location, away from the typical fossa ovalis region where most ASDs occur. 1
Transesophageal echocardiography is often required for accurate diagnosis, particularly to identify the defect location, assess the residual septal rims, and confirm pulmonary venous connections. 1, 6
Patients with unexplained right ventricular volume overload on TTE should undergo TEE or advanced imaging (cardiac MRI/CT) to rule out sinus venosus defects, as false-negative diagnoses are common with standard transthoracic imaging alone. 1, 6
Treatment Implications
Surgical closure with patch repair is the standard treatment (not percutaneous device closure, which is reserved for secundum ASDs), requiring surgeons with expertise in congenital heart disease. 1, 5
The surgical approach typically involves pericardial patch reconstruction to close the defect and redirect anomalous pulmonary venous drainage back to the left atrium. 5, 2
Surgical outcomes are excellent, with in-hospital mortality of 0.24% and 30-day mortality of 0.5%, though long-term complications include atrial fibrillation (3.3%), sinus node dysfunction (6.5%), and pacemaker requirement (2.23%). 3
Clinical Pitfall to Avoid
The most common diagnostic error is assuming all right ventricular volume overload with suspected ASD can be adequately evaluated by transthoracic echocardiography alone—sinus venosus defects require TEE or advanced imaging for definitive diagnosis, and missing this diagnosis delays appropriate surgical referral. 1, 6