Anatomy versus Shunt Fraction: Hemodynamic Consequences in Atrial Septal Defects and Partial Anomalous Pulmonary Venous Connection - A comprehensive CMR study

Aims: Atrial septal defect (ASD) and partial abnormal pulmonary venous connection (PAPVC) are noncyanotic congenital heart defects (CHD) that produce a left-to-right shunt. This single-center retrospective study aimed to assess the hemodynamic impact of isolated ASD, isolated PAPVC, and ASD-associated PAPVC using cardiovascular magnetic resonance (CMR).

Methods and results: From our CMR registry (2002-2024), 110 patients were included: isolated ASD (n=64), isolated PAPVC (n=18), ASD-associated PAPVC (n=28, mostly sinus venosus septal defects). CMR included geometric assessment of the cardiac chambers and great vessels, assessment of ventricular function, and flow patterns through the systemic (Qs) and pulmonary circulation (Qp). Patients were compared to a 40 control subjects with normal CMR findings. Significant differences were observed between controls, isolated ASD, isolated PAPVC, and ASD-associated PAPVC groups in left ventricular end-diastolic volumes indexed to body surface area (BSA) 80 ml/m2 [75-90] vs. 71 ml/m2 [57-79] vs. 71 ml/m2 [63-80] vs. 64 ml/m2 [57-72], p<0.001), right ventricular end-diastolic volumes/BSA (82 ml/m2 [74-88] vs. 110 ml/m2 [101-127] vs. 150 ml/m2 [120-165] vs. 154 ml/m2 [128-181], p<0.001), and Qp/Qs ratio (0.99 [0.95-1.01] vs. 1.49[1.34-1.67] vs. 1.96 [1.55-2.40] vs. 2.15 [1.81-2.64], p<0.001). No significant modulating factors were found for cardiac chambers or great vessels geometry, ventricular function, or flow patterns between the patient groups.

Conclusion: Despite phenotypic differences, no specific anatomical influences were found, suggesting that outcomes in isolated ASD, isolated PAPVC, and ASD-associated PAPVC are mainly driven by the degree of shunting.