Afterload is defined as the

Afterload is defined as the

• A. The volume of blood in the ventricle at end-diastole
• B. Total resistance the heart must overcome to eject blood
• C. The force of myocardial contraction
• D. The heart rate

Answer: (B)

Afterload is the pressure the ventricle has to overcome during systole to eject blood. It basically reflects the total resistance in the arterial system—the arterial pressure and systemic vascular resistance the heart must push against to open the aortic valve and move blood forward. That makes the description “the total resistance the heart must overcome to eject blood” the best fit. The other ideas describe different things: the volume in the ventricle at end-diastole is preload (the filling pressure/volume), the force of myocardial contraction is contractility, and heart rate is simply how fast the heart beats. These factors are not what the ventricle must overcome to eject blood, which is why they aren’t afterload.

Afterload is the pressure the ventricle has to overcome during systole to eject blood. It basically reflects the total resistance in the arterial system—the arterial pressure and systemic vascular resistance the heart must push against to open the aortic valve and move blood forward. That makes the description “the total resistance the heart must overcome to eject blood” the best fit.

The other ideas describe different things: the volume in the ventricle at end-diastole is preload (the filling pressure/volume), the force of myocardial contraction is contractility, and heart rate is simply how fast the heart beats. These factors are not what the ventricle must overcome to eject blood, which is why they aren’t afterload.