What is the Difference Between Unstable Angina and Myocardial Infarction?

Unstable angina and myocardial infarction (MI), also known as heart attack, are both acute coronary syndromes that involve an imbalance of supply and demand of oxygen available to the myocardium. They share similarities but have distinct differences:

Unstable Angina:

• It occurs when blood flow to the heart decreases, but it's not severe enough to cause cell death or a heart attack.
• There is myocardial ischemia without cardiac biomarkers of myocardial necrosis, such as creatine kinase MB isozyme, troponin, or myoglobin.
• Symptoms may occur at rest, become more frequent, severe, or prolonged than the usual pattern of angina, change from the usual pattern of angina, or not respond to rest or nitroglycerin.
• It belongs to the spectrum of clinical presentations referred to collectively as acute coronary syndromes, which also include STEMI (ST-segment elevation MI) and non-STEMI (NSTEMI).

Myocardial Infarction (MI):

• It happens when cell death damages or destroys heart tissue, usually due to a blood clot formation after a fatty deposit ruptures or splits.
• The distinguishing feature between unstable angina and non-STEMI or STEMI (types of MI) is the presence of elevated cardiac markers, such as troponin, which imply myocardial damage.

Symptoms of acute coronary syndromes are similar and may include chest pain or discomfort, pain or pressure in the back, neck, jaw, abdomen, shoulders, or arms, sweating, dyspnea, nausea, vomiting, dizziness, or sudden weakness. It is usually impossible to distinguish these syndromes based on symptoms alone. Diagnosis requires a combination of patient history, ECG results, and biomarkers.

Comparative Table: Unstable Angina vs Myocardial Infarction

Unstable angina and myocardial infarction (MI) are both acute coronary syndromes that result from a sudden blockage in a coronary artery. However, there are differences between the two conditions. Here is a table comparing the key differences between unstable angina and myocardial infarction:

In summary, unstable angina is characterized by chest pain or discomfort without a specific cause and is relieved with rest or nitroglycerin, whereas myocardial infarction involves complete blockage of blood supply to the heart, causing cell death. Unstable angina is generally considered less severe than MI, as it does not result in permanent damage to the heart.