Afterload is best described as which of the following?

Afterload is best described as which of the following?

• A. The volume in the ventricle at end of diastole.
• B. The heart rate independent of preload.
• C. Composed of peripheral vascular resistance and the tension in the ventricular wall; increases with distention and vasoconstriction, increasing myocardial oxygen demand.
• D. The speed of electrical impulse through the AV node.

Answer: (C)

Afterload is the pressure the ventricle must overcome to eject blood during systole. This depends mainly on systemic vascular resistance and the arterial pressure the ventricle pumps against. The wall stress the ventricle must generate to push blood out increases with higher vascular resistance and with ventricular dilation, which raises the tension the heart must develop. Therefore, when afterload rises, the heart works harder and myocardial oxygen demand increases. This fits best with the description that includes peripheral vascular resistance and ventricular wall tension, noting that afterload increases with vasoconstriction and chamber distention. The other descriptions refer to preload (the volume in the ventricle at end of diastole) or to aspects of conduction, which are not afterload.

Afterload is the pressure the ventricle must overcome to eject blood during systole. This depends mainly on systemic vascular resistance and the arterial pressure the ventricle pumps against. The wall stress the ventricle must generate to push blood out increases with higher vascular resistance and with ventricular dilation, which raises the tension the heart must develop. Therefore, when afterload rises, the heart works harder and myocardial oxygen demand increases.

This fits best with the description that includes peripheral vascular resistance and ventricular wall tension, noting that afterload increases with vasoconstriction and chamber distention. The other descriptions refer to preload (the volume in the ventricle at end of diastole) or to aspects of conduction, which are not afterload.