A left-to-right tissue shunt, such as an arteriovenous fistula, physiologically resembles which of the following?

A left-to-right tissue shunt, such as an arteriovenous fistula, physiologically resembles which of the following?

• A. Left-to-right intracardiac shunt
• B. Right-to-left intracardiac shunt
• C. Ventilation of unperfused alveoli
• D. Pulmonary embolism

Answer: (A)

The main idea is that a left-to-right tissue shunt, such as an arteriovenous fistula, bypasses tissue capillaries so oxygenated arterial blood returns to the venous side rather than delivering O2 to the tissue. This is functionally similar to a left-to-right intracardiac shunt, where oxygen-rich blood is redirected back into the right heart and lungs instead of perfusing systemic tissues. In both cases, the arterial oxygen content remains high, but some of the blood that should go to tissues circulates back through the venous/pulmonary circulation. This contrasts with a right-to-left shunt, which dumps deoxygenated blood into the systemic circulation and causes hypoxemia, and with ventilation of unperfused alveoli or a pulmonary embolism, which are not true shunts but involve V/Q mismatch or dead space perfusion.

The main idea is that a left-to-right tissue shunt, such as an arteriovenous fistula, bypasses tissue capillaries so oxygenated arterial blood returns to the venous side rather than delivering O2 to the tissue. This is functionally similar to a left-to-right intracardiac shunt, where oxygen-rich blood is redirected back into the right heart and lungs instead of perfusing systemic tissues. In both cases, the arterial oxygen content remains high, but some of the blood that should go to tissues circulates back through the venous/pulmonary circulation. This contrasts with a right-to-left shunt, which dumps deoxygenated blood into the systemic circulation and causes hypoxemia, and with ventilation of unperfused alveoli or a pulmonary embolism, which are not true shunts but involve V/Q mismatch or dead space perfusion.