How dangerous is high Qp/Qs in atrial septal defects?

Question

Hello doctor,

For a left-to-right shunt in an atrial septal defect with a Qp/Qs ratio of two, does it mean that the amount of blood flowing through the lungs is twice the amount flowing to the rest of the body? If the total cardiac output is divided into three parts, with two parts going to the lungs and one part to the body, then the lungs receive about 66 percent, and the body receives about 33 percent of the blood output. Is this correct? What about a Qp/Qs ratio of seven? Could this lead to hypoperfusion?

Please help.

Answer 1

Hello,

Welcome to icliniq.com.

I understand your concern.

Regarding a high Qp: Qs (pulmonary-to-systemic blood flow ratio) (seven), meaning your pulmonary circulation is seven times greater than your systemic circulation, it would typically indicate a risk of pulmonary hypertension, pulmonary artery dilation, strain on the right heart, right-sided chamber dilation, and eventually reduced heart function.

Similarly, with blood shunting from the left to the right side, there would typically be less blood supplied to the body compared to the lungs. If growth and development remain unaffected despite this, it suggests the heart has somehow managed to meet the body's requirements even with less oxygenated blood. Hypoxia could occur if the shunt were to reverse, which means instead of left to right, it reverses to right to left.

Right heart failure is a long-term complication where the chronic volume overload on the right side of your heart (right ventricle) may eventually cause it to dilate, reducing its function and potentially leading to hypoperfusion and cardiogenic shock due to inadequate filling of the left heart (left ventricle).

I hope this helps. Please follow up if you have any further concerns.