Nitroglycerin primarily reduces which hemodynamic parameter to lower myocardial oxygen demand?

Nitroglycerin primarily reduces which hemodynamic parameter to lower myocardial oxygen demand?

• A. Preload
• B. Afterload
• C. Heart rate
• D. Contractility

Answer: (A)

Nitroglycerin works mainly as a venodilator, pulling blood into the venous system and reducing venous return to the heart. This lowers the left ventricular end-diastolic pressure and volume, which decreases wall stress (the tension the heart has to generate). Because myocardial oxygen consumption tracks with wall stress and filling pressures, reducing preload substantially lowers myocardial oxygen demand. While nitrates can influence afterload at higher doses, their primary hemodynamic effect at typical clinical doses is preload reduction, which is why this option best fits the goal of decreasing oxygen demand. Heart rate and contractility aren’t directly reduced by nitrates, and any decrease in afterload is not the main mechanism at usual doses.

Nitroglycerin works mainly as a venodilator, pulling blood into the venous system and reducing venous return to the heart. This lowers the left ventricular end-diastolic pressure and volume, which decreases wall stress (the tension the heart has to generate). Because myocardial oxygen consumption tracks with wall stress and filling pressures, reducing preload substantially lowers myocardial oxygen demand. While nitrates can influence afterload at higher doses, their primary hemodynamic effect at typical clinical doses is preload reduction, which is why this option best fits the goal of decreasing oxygen demand. Heart rate and contractility aren’t directly reduced by nitrates, and any decrease in afterload is not the main mechanism at usual doses.