Nitroglycerin’s mechanism in ischemic heart disease includes which effect?

Nitroglycerin’s mechanism in ischemic heart disease includes which effect?

• A. It increases afterload
• B. It decreases heart rate
• C. It dilates veins reducing preload
• D. It constricts arteries

Answer: (C)

Nitrates relieve angina mainly by lowering myocardial oxygen demand through venodilation. Nitroglycerin releases nitric oxide, which relaxes vascular smooth muscle, and at typical therapeutic doses it dilates veins more than arteries. This venodilation reduces venous return to the heart, decreasing left ventricular end-diastolic volume and pressure (preload). With less wall tension and lower LV filling pressures, the heart works more efficiently and needs less oxygen, which helps alleviate ischemia. Although nitrates can cause some arterial dilation at higher doses and may lead to reflex tachycardia from the drop in blood pressure, the primary and most consistent effect relevant to ischemic heart disease is reduced preload. They do not constrict arteries, and they do not directly decrease heart rate.

Nitrates relieve angina mainly by lowering myocardial oxygen demand through venodilation. Nitroglycerin releases nitric oxide, which relaxes vascular smooth muscle, and at typical therapeutic doses it dilates veins more than arteries. This venodilation reduces venous return to the heart, decreasing left ventricular end-diastolic volume and pressure (preload). With less wall tension and lower LV filling pressures, the heart works more efficiently and needs less oxygen, which helps alleviate ischemia.

Although nitrates can cause some arterial dilation at higher doses and may lead to reflex tachycardia from the drop in blood pressure, the primary and most consistent effect relevant to ischemic heart disease is reduced preload. They do not constrict arteries, and they do not directly decrease heart rate.