When a hole allows for communication (blood shunting)... extra volume ends up where it shouldn't be

Higher pressure in left side compared to right side ➔ blood moves from LEFT (high) ➔ RIGHT (low) (Qp > Qs)

Already oxygenated blood moves back to right side ➔ ↑ right sided volume & pressure ➔ ↑ pulmonary blood flow (↑  Qp)  

↑ Qp ➔ pulmonary HTN over time ➔ increased pulmonary vasculature on CXR

• Qp: pulmonary flow (from heart to lungs) Qs: systemic flow (from heart to body); Normally 1:1 

  • Qp > Qs = pulmonary flow > systemic flow = Left ➔ Right shunt 

  • Qp < Qs = pulmonary flow < systemic flow = Right ➔ Left shunt 

Pulmonary over-circulation ➔ dyspnea (bobbing head, nasal flaring, retractions), ↑ respiratory infections

When CO ↓ ➔ sweating, exertional dyspnea (babies exert themselves while feeding)

RAE ➔ arrhythmias

Pulmonary HTN ➔ pulmonary vessel remodeling ➔ RVH to overcome pressure 

Once RV pressure > LV pressure ➔ reversal of shunt (Qp < Qs) ➔ cyanosis ➔ polycythemia, finger clubbing...    

• Eisenmenger syndrome: Acyanotic defect becomes cyanotic defect (when shunt reverses) 

  • CLOSURES ARE CONTRAINDICATED ONCE THIS HAPPENS

  • Only tx is lung transplant + repair defect or lung & heart transplant

Abnormal cardiac development can cause connections between R and L heart

Right ➔ left shunting ➔ cyanosis ➔  blue babies with failure to thrive and sx of HF