In a patient with high MAP and high SVR due to an afterload problem, what is the expected effect of a vasodilator?

In a patient with high MAP and high SVR due to an afterload problem, what is the expected effect of a vasodilator?

• A. Increase MAP
• B. Decrease SVR and MAP with an increase in SV and CO
• C. No change
• D. Increase PCWP

Answer: (B)

The main idea being tested is how lowering afterload with a vasodilator changes hemodynamics when systemic vascular resistance and MAP are high. A vasodilator decreases SVR, easing the left ventricle’s job of ejecting blood. This improves stroke volume and thus increases cardiac output. Since MAP is roughly CO × SVR, lowering SVR tends to reduce MAP unless CO rises enough to offset it; in this scenario CO does rise, but the fall in SVR is still enough that MAP decreases overall. Vasodilators don’t raise left atrial pressure, so an increase in PCWP is not expected. Therefore, the best description is that SVR and MAP decrease while stroke volume and CO increase.

The main idea being tested is how lowering afterload with a vasodilator changes hemodynamics when systemic vascular resistance and MAP are high. A vasodilator decreases SVR, easing the left ventricle’s job of ejecting blood. This improves stroke volume and thus increases cardiac output. Since MAP is roughly CO × SVR, lowering SVR tends to reduce MAP unless CO rises enough to offset it; in this scenario CO does rise, but the fall in SVR is still enough that MAP decreases overall. Vasodilators don’t raise left atrial pressure, so an increase in PCWP is not expected. Therefore, the best description is that SVR and MAP decrease while stroke volume and CO increase.