The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 62

76. Is it true that allergic reactions can cause heart attacks?

  • Yes.
  • Kounis Syndrome is an acute coronary syndrome caused by activated mast cells releasing chemicals. It is sometimes referred to as “allergic heart attack.” In acute coronary syndrome, there is not enough blood being pumped into the heart. It is named for two of the large blood vessels supplying oxygen to the heart, the coronary arteries. When not enough blood is getting to the heart via the coronary arteries, it can damage heart muscle, sometimes permanently. Heart attack and angina are examples of acute coronary syndromes.
  • In Kounis Syndrome, mast cells become activated, releasing lots of chemicals. These chemicals can irritate the coronary artery, causing it to spasm. This spasm reduces the amount of blood getting to the heart. Sometimes, mast cell activation can trigger the formation of a clot. A clot can be the reason not enough blood is passing through the artery.
  • Several of the molecules released by mast cells can affect the cardiovascular system and contribute to causing Kounis Syndrome. Histamine and leukotrienes can cause the coronary artery to narrow. It can also activate platelets, helping a clot to form. Both tryptase and chymase can cause clots formed elsewhere to break off and get stuck in the coronary artery.
  • Mast cells also help regulate an important molecule called angiotensin II. Angiotensin II is a powerful regulator of blood pressure and can cause the coronary artery to narrow and tighten up.
  • People with Kounis Syndrome may have a history of coronary artery disease. Some patients have a stent in the coronary artery from a previous coronary issue. A stent is a tube that helps keep the blood vessel the right size so that the heart gets the blood it needs. However, many patients with Kounis Syndrome do not have any history of problems with their heart or blood vessels.
  • The symptoms of Kounis Syndrome sometimes look just like the symptoms of any other mast cell reaction or anaphylaxis, making it hard to know that a person is having Kounis Syndrome. Chest pain, irregular heart beat, the heart beating too fast or too slow, and palpitations are all common symptoms of Kounis Syndrome.
  • Another tricky thing about Kounis Syndrome is that it doesn’t always show up on the tests we use to look for heart attack or coronary issues. Because of this, doctors don’t always realize what is happening. Some people do have positive results to these tests, things like EKG, echocardiogram, chest x-ray, and bloodwork to look at levels at cardiac enzymes or troponin. Cardiac enzymes and troponins are often high in a person who is having a heart attack but are sometimes normal for patients with Kounis Syndrome.
  • In order to manage Kounis Syndrome, patients may need treatment for both the allergic reaction and the coronary syndrome.
  • Treatment for the allergic reaction is similar to anaphylaxis treatment: an H1 antihistamine like Benadryl, an H2 antihistamine like famotidine, a corticosteroid like methylprednisolone, IV fluids, and sometimes epinephrine, if that’s appropriate. Please note that epinephrine is not always appropriate for patients who have Kounis Syndrome because epinephrine can actually also cause the coronary artery to narrow.
  • Treatment for the cardiovascular aspect of Kounis Syndrome is very dependent upon symptoms and test results. Calcium channel blockers like verapamil, aspirin, and nitroglycerin are commonly used. Importantly, some of the common medications used to manage coronary syndrome are not safe for mast cell patients. These medications include beta blockers like metoprolol or atenolol, and, to a lesser extent, ACE inhibitors like lisinophil. These medications can interfere with epinephrine so epinephrine may not work if a patient needs it for anaphylaxis.
  • Anything that triggers mast cell activation can cause Kounis Syndrome, including emotional stress.

For additional information, please visit the following posts:
Kounis Syndrome: Subtypes and effects of mast cell mediators (Part 1 of 4)
Kounis Syndrome: Diagnosis (Part 2 of 4)
Kounis Syndrome: Treatment (Part 3 of 4)
Kounis Syndrome: Stress (Part 4 of 4)
Beta blockers and epinephrine
Cardiovascular manifestations of mast cell disease: Part 1 of 5
Cardiovascular manifestations of mast cell disease: Part 2 of 5
Cardiovascular manifestations of mast cell disease: Part 3 of 5
Cardiovascular manifestations of mast cell disease: Part 4 of 5
Cardiovascular manifestations of mast cell disease: Part 5 of 5
The Provider Primers Series: Medications that impact mast cell degranulation and anaphylaxis