After a cause of angina is found, one big distinction is whether the chest pain is stable or unstable. Stable angina occurs predictably, when the heart is working harder, and it usually is short (sometimes less than 5 minutes). Rest and medicine relieve the pain, which is similar every time it occurs.
Unstable angina, though, occurs at rest—even during sleep—and can be a surprise. This type lasts longer, can worsen with time, and doesn’t get better with rest or medicine.