What is a key way to differentiate between angina and a myocardial infarction (MI)?

One of the most important distinctions between angina and a myocardial infarction lies in the response of the symptoms to nitroglycerin and rest. Angina, which is often caused by temporary ischemia of the heart muscle, typically presents as a sharp, crushing chest pain that can be relieved by rest and the administration of nitroglycerin. This is because nitroglycerin works by dilating blood vessels, thus improving blood flow to the heart muscle during times of increased demand or when there is an obstruction.

In contrast, a myocardial infarction results from prolonged ischemia leading to damage of the heart muscle. The chest pain associated with an MI is often more severe and does not improve significantly with rest or nitroglycerin. Therefore, assessing the relief of pain through these interventions serves as a key diagnostic tool in differentiating between angina and a myocardial infarction.

Other options, such as checking for a heart murmur, observing swelling in the legs, or monitoring blood glucose levels, do not provide direct insight into the nature of the chest pain or the underlying cardiac issue in question.