The level of activity or stress that provokes the angina is somewhat predictable, and the pattern changes only slowly. It is the most common variety and is not very dangerous. Unstable angina, instead of appearing gradually, may first appear as a very severe episode or as frequently recurring bouts of angina. The established stable pattern of angina may change sharply. This may be provoked by an exercise or it may appear at rest.
Unstable angina is very dangerous and can even lead to the death of the patient.
There are two other forms of angina pectoris. This is a recurring pain which narrows the coronary artery and lessens the flow of blood to the heart. The other is a recently discovered type of angina called micro-vascular angina . In this, patients experience chest pain, but have no apparent coronary artery blockages. Studies have revealed that the pain results from poor function of tiny blood vessels nourishing the heart as well as the arms and legs.