MINOCA : When a heart attack is not a heart attack
The term MINOCA stands for Myocardial infarction with non-obstructive coronary arteries.
Ill try and explain this a bit better by using a case study.
A 50 year old lady was admitted to my hospital with crushing ches tightness. She had an ECG which suggested changes in keeping with a lack of blood getting to the heart. She had a blood test to measure Troponin. Troponins are enzymes released from the heart when the heart has been damaged. In this lady the troponin was found to be elevated. On the basis of these findings we told her that she had suffered a heart attack. She asked me why I felt she had had a heart attack and I explained to her that she had had chest pains and the blood test indicating damage to the heart was elevated and that was all we needed to say that she had had a heart attack. Clearly quite upset, she asked me what would happen next and i said to her that the heart attack was probably caused by a very severe narrowing or even a blockage of one or more of the blood vessels that supplied blood to the heart and the next step would be to do a test called an angiogram to look at her coronary vessels, identify exactly where the narrowings were and fix them. She agreed and we performed an angiogram and we were fully expecting a blockage but interestingly there weren’t any. She had some very minor plaque but certainly nothing that could explain the heart attack and therefore she was discharged with a diagnosis of MINOCA i.e to all intents and purposes she had a heart attack but without significant obstructive disease in her coronaries.
We have known that patients can present with heart attacks in the absence of obstructive coronary disease for over 80 years but the term MINOCA has been adopted for about the past 7-8 years.
MINOCA is not an uncommon diagnosis. Up to 5-15% of all patients who present with heart attacks are found to have unobstructed coronary vessels and therefore diagnosed with MINOCA. The big problem is that as nothing major is found, there is nothing to fix and this leaves the poor patient feeling very perplexed and uncertain about their future.
Whilst traditional heart attacks are seen in older patients and more men than women, MINOCA is seen more often in younger women . Genetics and physiological stress are also risk factors.
Whilst it is reassuring to find that the heart arteries are not obstructed, MINOCA should not be considered a benign diagnosis because the heart has still suffered damage and the areas of damage can cause the heart to become irritable and cause dangerous heart rhythm disturbances. In addition, the heart can still be left weak and of course, the underlying problem can still manifest with another ‘heart attack’ and more damage in the future.
It is important for me to stress that MINOCA is not a complete diagnosis in itself but rather an umbrella term for patients who present like the lady I mentioned earlier did. There are lots of underlying causes that could explain MINOCA and this is why the diagnosis of MINOCA should prompt more detailed and more sophisticated investigation.
The causes can be divided into 3 groups:
Coronary causes
Cardiac Causes
Non-Cardiac Causes
