What are the types of heart attacks?

What are the types of heart attacks?

(Please see the YouTube video above for illustrations)

Most of us would think that heart attack is just one disease. World Heart Federation along with major European and North American Heart Societies have brought forth the universal definition of myocardial infarction, the technical name for heart attack. It has been revised the fourth time in 2018. In the latest revision heart attacks have been classified into 5 types, of which type 4 has three subtypes as well.

Type 1 is the type of heart attack which all of us are familiar with. It occurs due to obstruction of a blood vessel supplying oxygenated blood to the heart muscle. This leads to chest pain and ECG changes. Heart muscle damage can be noted on ultrasound imaging of the heart as well as other imaging modalities like magnetic resonance imaging (MRI). A clot is observed within the blood vessel on X-ray imaging known as coronary angiography.

Type 2 occurs when there is supply-demand mismatch. Sudden loss of a lot of blood from the body due to any bleeding can reduce the supply of oxygen to the heart muscle and consequent damage. Type 2 is more common in women and has poorer outcome due the often associated other ailments.

In type 3, death occurs before blood troponin test which is essential for the diagnosis of a heart attack can become positive. The person would have chest pain and early ECG changes, though the troponin evidence is lacking.

Type 4a is a heart attack associated with procedures for removing blocks in blood vessels like coronary angioplasty. They will have symptoms and ECG changes as in type 1. Coronary angiogram will show a fresh block in a blood vessel which is related to the procedural complication.

In type 4b a stent or spring link material implanted during an angioplasty procedure gets blocked later due to clot formation inside it. This is known as stent thrombosis.

Type 4c is caused by narrowing of a region of blood vessel in which stent has been implanted by growth of cells into it. This is documented by coronary angiogram.

Type 5 is associated with coronary artery bypass grafting (CABG). It is also documented by ECG and coronary angiogram. Ultrasound or other imaging studies will show the new damage to heart muscle.

Documentation of heart attack in all these types needs a blood test known as cardiac troponin in addition to other evidence, except in type 3. Troponin levels rise in a delayed pattern after a heart attack, reaching a peak at 24 hours. So, in type 3, the levels do not reach diagnostic levels due to early death. Cardiac troponin is a heart muscle protein released into the blood after damage to heart muscle.