Why is the right ventricle more susceptible to increases in afterload?

• A. The RV has thicker walls and operates in a high-pressure systemic circuit.
• B. The RV has more coronary perfusion than the left ventricle.
• C. The RV has thinner walls and operates in a low-pressure pulmonary circuit.
• D. Increased pulmonary vascular resistance lowers RV afterload.

Answer: (C)

Afterload and the right ventricle’s normal design go hand in hand here. The right ventricle normally pumps into the lungs, where the pulmonary circulation offers relatively low resistance, and it has thinner walls with less muscular mass. When pulmonary vascular resistance climbs, the ventricle must generate much higher pressure to eject blood. Its thinner walls mean less muscle to produce that pressure and less reserve to cope with the sudden rise in workload, so its stroke volume falls and the ventricle can dilate and fail. The left ventricle, by contrast, has thick, muscular walls built to produce high pressures for the systemic circuit, so it handles increases in afterload more effectively. Hence, the right ventricle is more susceptible to increases in afterload.