According to Frank-Starling curves, which ventricle yields higher cardiac output at the same filling pressure?

According to Frank-Starling curves, which ventricle yields higher cardiac output at the same filling pressure?

• A. Left ventricle
• B. Right ventricle
• C. Both ventricles yield the same cardiac output at the same filling pressure.
• D. Neither ventricle responds to preload changes.

Answer: (B)

The key idea is how preload and afterload shape the heart’s response to filling. The Frank-Starling mechanism says that increasing how much the ventricle fills (preload) stretches the muscle fibers and raises the force of contraction, boosting stroke volume and cardiac output. But the amount of output you get from that filling also depends on the pressure the ventricle has to push against—afterload. The right ventricle pumps into the low-resistance pulmonary circuit, while the left ventricle works against the high-resistance systemic circulation. With the same filling pressure, the right ventricle faces a smaller afterload, so a larger portion of its end-diastolic volume is ejected. That means its stroke volume—and thus cardiac output—will be higher at that same preload compared with the left ventricle. The left ventricle, dealing with greater afterload, ejects a smaller fraction of its filling, resulting in lower output at the same preload. In short, at equal filling pressures, the right ventricle can convert preload into a higher cardiac output due to the lower afterload it encounters.

The key idea is how preload and afterload shape the heart’s response to filling. The Frank-Starling mechanism says that increasing how much the ventricle fills (preload) stretches the muscle fibers and raises the force of contraction, boosting stroke volume and cardiac output. But the amount of output you get from that filling also depends on the pressure the ventricle has to push against—afterload.

The right ventricle pumps into the low-resistance pulmonary circuit, while the left ventricle works against the high-resistance systemic circulation. With the same filling pressure, the right ventricle faces a smaller afterload, so a larger portion of its end-diastolic volume is ejected. That means its stroke volume—and thus cardiac output—will be higher at that same preload compared with the left ventricle. The left ventricle, dealing with greater afterload, ejects a smaller fraction of its filling, resulting in lower output at the same preload.

In short, at equal filling pressures, the right ventricle can convert preload into a higher cardiac output due to the lower afterload it encounters.