What term describes the resistance the heart must overcome to eject blood?

• A. Preload
• B. Stroke volume
• C. Cardiac output
• D. Afterload

Answer: (D)

Afterload is the resistance the heart must overcome to eject blood. It represents the arterial pressure the ventricle must generate during systole to open the outflow valve and push blood into the aorta (or pulmonary artery). When systemic vascular resistance or arterial pressure rises, afterload increases, making it harder for the ventricle to eject blood and potentially lowering stroke volume if contractility can’t compensate. Preload is about filling the ventricle at the end of diastole, stroke volume is how much blood is ejected per beat, and cardiac output is the amount ejected per minute (stroke volume times heart rate). Higher afterload occurs with hypertension or valvular/arterial resistance, while vasodilators can reduce afterload and improve ejection.