What is the significance of right to left shunting in Tetralogy of Fallot?

In Tetralogy of Fallot, right-to-left shunting occurs due to the combination of four cardiac anomalies, which includes a ventricular septal defect (VSD) and a right ventricular outflow tract obstruction. This type of shunting is significant because it causes deoxygenated blood from the right side of the heart to flow directly into the left side and subsequently into the systemic circulation.

As a result, the blood that is pumped out to the body is not properly oxygenated, leading to decreased oxygen levels in the bloodstream. This process inherently decreases the amount of blood flow that reaches the lungs for oxygenation, particularly during episodes that can further obstruct blood flow, such as when the right ventricular outflow tract is narrowed.

Understanding the effects of right-to-left shunting helps in managing the clinical features of Tetralogy of Fallot, such as cyanosis and the risk of hypoxic spells, especially during exertion or stressful situations. The pathophysiology revolving around this shunting is central to the outcomes seen in patients with this congenital heart defect.