How does nitroglycerin primarily affect a patient?

Nitroglycerin primarily acts as a vasodilator, which means it relaxes and widens the blood vessels. This effect is particularly significant in the coronary arteries, which supply blood to the heart muscle itself. By dilating these arteries, nitroglycerin increases blood flow to the heart, enhancing oxygen delivery, and alleviating angina chest pain. This mechanism is crucial for patients with conditions like coronary artery disease, where blood flow is often restricted.

While nitroglycerin can cause headaches and flushing due to its vasodilatory effects, these are secondary effects and not its primary action. The drug can also lead to increased heart rate as a compensatory response to the drop in blood pressure caused by vasodilation, but this is not the primary way it affects a patient. Thus, the most accurate answer is that nitroglycerin actively dilates coronary arteries, directly improving oxygen supply to the heart.