What is a physiologic effect of nitroglycerin?

What is a physiologic effect of nitroglycerin?

• A. Reduces preload
• B. Increases afterload
• C. Increases heart rate
• D. Decreases venous capacitance

Answer: (A)

Nitroglycerin’s main action is venodilation, which increases venous capacitance and lowers venous return to the heart. That drop in venous return reduces left ventricular end-diastolic volume and pressure, i.e., preload, which also decreases myocardial wall stress and oxygen demand. At higher doses it can dilate arteries and lower afterload, but the most consistent and clinically relevant effect is reduced preload. It may cause a reflex tachycardia from the blood pressure drop, but it does not inherently increase heart rate. The reduction of preload best captures its primary physiologic effect.

Nitroglycerin’s main action is venodilation, which increases venous capacitance and lowers venous return to the heart. That drop in venous return reduces left ventricular end-diastolic volume and pressure, i.e., preload, which also decreases myocardial wall stress and oxygen demand. At higher doses it can dilate arteries and lower afterload, but the most consistent and clinically relevant effect is reduced preload. It may cause a reflex tachycardia from the blood pressure drop, but it does not inherently increase heart rate. The reduction of preload best captures its primary physiologic effect.