Which statement best defines afterload?

• A. End diastolic volume
• B. Total peripheral resistance
• C. Cardiac contractility
• D. Venous return

Answer: (B)

Afterload is the pressure the left ventricle must overcome to eject blood during systole, and in the systemic circulation this load is mainly set by arterial pressure and the resistance the arteries provide. That’s why total peripheral resistance is the best descriptor of afterload—it captures the overall opposition the ventricle faces from the vasculature.

End diastolic volume reflects preload—the filling pressure before contraction—rather than the pressure the heart must push against. Cardiac contractility describes the heart muscle’s intrinsic ability to contract, independent of the load. Venous return concerns how much blood returns to the heart to fill it (affecting preload), not the resistance against which the heart must eject.