Unstable angina is a serious medical condition that requires immediate attention, as it is considered a medical emergency. It occurs when the blood flow to the heart is suddenly blocked or reduced, leading to chest pain or discomfort. Unstable angina is different from stable angina, which usually occurs during physical activity or emotional stress and goes away with rest or medication. Unlike stable angina, unstable angina is unpredictable and can occur at any time, even at rest. Nitroglycerin can provide temporary relief, but it does not address the underlying cause of the condition. Treatment for unstable angina may include medications, lifestyle changes, and medical procedures such as angioplasty or coronary artery bypass surgery.