Quantifying right atrial dilation relative to atrial septal defect size using an experimental model

Atrial septal defect (ASD) is a congenital cardiovascular defect in the septum between the heart’s upper chambers. Larger ASDs cause significant dilation in the right atrium, which can lead to heart failure and pulmonary hypertension. Current methods poorly predict the severity of right atrial dilation based on ASD size because external physiological variables confound the relationship. Understanding the relationship between ASD size and right atrium dilation would improve assessments of prognosis and treatment plans. This experiment quantifies the relationship between ASD size and right atrial dilation using an experimental model by measuring how the defect size affects right atrial fluid output. We hypothesized that larger ASDs result in greater, linearly increasing right atrium fluid output. We constructed the model using two fluid-filled chambers, scaled to represent the left and right atria, and simulated the ASD size by drilling incrementally larger openings between the chambers. In addition, we maintained fluid pressure separately, attuned to cardiovascular blood pressure, to mimic a realistic atrial setting. The findings support our hypothesis: across apertures of 6, 10, and 14 mm, right atrial fluid output increased with ASD diameter. These results provide a quantifiable relationship between ASD size and right atrial fluid output, presenting a cost-effective model to offer insight into ASD’s effect on right atrial shunt, and inform clinical prognosis for ASD patients.