NHS UK lists the three main types of acute coronary syndrome (ACS):
- ST segment elevation myocardial infarction (STEMI)
- non-ST segment elevation myocardial infarction (NSTEMI)
- unstable angina
ST segment elevation myocardial infarction (STEMI)
An STEMI is the most serious type of heart attack where there is a long interruption to the blood supply. This is caused by a total blockage of the coronary artery, which can cause extensive damage to a large area of the heart. An STEMI is what most people think of when they hear the term “heart attack”.
Non-ST segment elevation myocardial infarction (NSTEMI)
An NSTEMI can be less serious than an STEMI because the supply of blood to the heart may be only partially, rather than completely, blocked. As a result, a smaller section of the heart may be damaged. However, an NSTEMI is still regarded as a serious medical emergency. Without treatment, it can progress to serious heart damage or STEMI.
Unstable angina is the least serious type of ACS. However, like NSTEMI, it is still a medical emergency as it can also progress to serious heart damage or STEMI. In unstable angina, the blood supply to the heart is still seriously restricted, but there is no permanent damage, so the heart muscle is preserved.