There are several types of angina.
Stable or chronic angina
Stable angina occurs when the heart is working harder than usual, for instance, during exercise. It has a regular pattern and can be predicted to happen over months or even years. Rest or medication relieves symptoms.
Unstable angina does not follow a regular pattern. It can occur when at rest and is considered less common and more serious because rest and medication do not relieve it. This version can signal a future heart attack within a short time - hours or weeks.
Variant and microvascular angina
Variant or Prinzmetal's angina and microvascular angina are rare and can occur at rest without any underlying coronary artery disease. This angina is usually due to abnormal narrowing or relaxation of the blood vessels, reducing blood flow to the heart. It can be relieved by medicine.