MI and referred pain
EDP column by Dr Ketan Dhatariya

“My father was recently diagnosed as having a heart attack. His only symptom was being a little breathless. I thought that having a heart attack meant pain in the chest or in the arm, was I wrong?"

I am sorry to hear about your father, I hope he is recovering well. A heart attack is caused by a blockage or narrowing of the blood supply to the heart muscle. As the tissues are deprived of oxygen, the cells die off. As they die, they release a variety of substances that can trigger the nerves surrounding the heart, and eventually then nerves themselves can be deprived of oxygen long enough for them to die as well. It is the origin of these nerves that determines where pain is felt, this phenomenon is known as ‘referred pain’.

During development as an embryo the nerves develop from specialised tissues. As the body gets bigger, the nerves also enlarge, often taking long routes to get to places that would seem to be anatomically quite close by. The nerves emerge from along the developing spinal cord. Different nerves that emerge from the same place in the spinal cord often supply different areas, but the brain can occasionally confuse the signals that it receives. For example, the heart is supplied by nerves that share their origins along the spinal cord, with other nerves that supply sensation from the left arm or neck, thus, when the nerves around the heart are stimulated (for example by being deprived of oxygen) then the pain may be perceived as coming from the left arm or from the neck as well as from the chest. Another example is feeling pain at the right tip of your shoulder from gall bladder problems. This is because the nerves that supply sensation to the tip of the shoulder share their origin with nerves that supply the muscle that helps you breath, the diaphragm. If the gall bladder becomes inflamed, such as can happen if there are gall-stones present, then this can be felt as shoulder pain.

Having referred pain is not a bad thing. In the case of angina (the Latin word for pain) it can act as a warning. It tells the individual that something is wrong and that they need to seek help. However, there are a few conditions that can lead to the nerves being damaged and so not being able to give the warning signals when needed, examples of this include long term poorly controlled diabetes, or sometimes, just old age. Everyone is different and the same condition can lead to different symptoms in different people. If you suspect that something is ‘not quite right’, then there is no harm in paying a visit to your GP and letting them know your concerns.

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