What is the primary action of long-acting nitroglycerin in relieving angina?

The primary action of long-acting nitroglycerin in relieving angina is to dilate blood vessels, particularly the coronary arteries. This dilation enhances blood flow to the heart muscle, allowing for improved oxygen delivery during episodes of angina, which is typically caused by reduced blood flow due to coronary artery disease. By increasing the diameter of the coronary arteries, nitroglycerin effectively alleviates symptoms of angina, providing relief by addressing the underlying issue of inadequate blood supply to the myocardium.

While it is important to recognize that nitroglycerin does have effects on other vascular areas, the key role it plays in treating angina is its capacity to specifically target the coronary circulation. This is critical as angina results from insufficient perfusion to the heart muscle itself, making this action vital for symptomatic relief.

The other options do not align with the mechanism by which long-acting nitroglycerin alleviates angina. For example, enhancing myocardial contractility would not directly address the reduced blood flow that causes angina. Similarly, increasing systemic vascular resistance or raising blood pressure could further complicate or worsen the myocardial oxygen demand without relieving angina. Thus, the selective dilation of the coronary arteries is the most pertinent action that directly relates to