During atrial septal defect surgery, what ratio indicates the need for intervention?

In the context of atrial septal defects (ASD) and surgical intervention, the ratio of pulmonary-to-systemic blood flow (Qp/Qs) is a crucial factor. A ratio of 1:5 suggests that for every five units of blood flowing through the systemic circulation, only one unit is passing through the pulmonary circulation. This indicates a significant imbalance where the pulmonary circulation is receiving an excess amount of blood flow relative to systemic circulation, typically seen as a consequence of left-to-right shunting due to an ASD.

When the Qp/Qs ratio exceeds certain thresholds, particularly greater than 1.5:1 to 2:1, it signifies that the left-to-right shunt is substantial enough to justify intervention to prevent complications like volume overload of the right heart and pulmonary hypertension. A ratio of 1:5, indicating a level of imbalance that can lead to progressive health issues, would therefore strongly advocate for surgical correction to restore hemodynamic balance.

In summary, the ratio of 1:5 indicates a very high degree of shunting and dysfunction, making intervention necessary to prevent long-term complications that could arise from the physiology of the defect.