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Anaphylaxis: the heart of the matter

Anaphylaxis: the heart of the matter

The severe allergic reaction that develops due to several stimuli could cause heart rate and rhythm disorder, and in some cases, heart failure

The rare but severe allergic reaction anaphylaxis which could result in severe cardiac shock and heart attack has become a major cause of worry during the pandemic

In early 2022, a 29-year-old covid positive man arrived at a hospital in Khar, Mumbai, complaining of severe chest pain and breathlessness 24 hours after receiving his covid booster shot. “His ECG revealed that he had heart attack symptoms. His front artery, the LAD, had a significant clot, the angiogram revealed. Doctors had to suck the clot out, but he didn’t require a stent because a stent is put where there are blockages, but this was just a clot. So, once the clot was out, he stabilised and was discharged,” recounts Dr Nilesh Gautam, consultant, interventional cardiology, PD Hinduja Hospital & Medical Research Centre, Khar, Mumbai, the doctor who treated him.

Explaining further, Dr Gautam says, “Any vaccine is a foreign protein that we are injecting into the body. Some people may experience anaphylaxis after receiving the covid vaccine, or any vaccine for that matter. Having said that, we have seen people in whom covid vaccines caused anaphylactic complications. We have seen an increase in clot formation in them. We know covid as a virus is a procoagulant, which means that an individual infected with covid tends to form clots, which we saw many times, especially the omicron variant.”

The US Centre for Disease Control and Prevention (CDC) charted out a separate set of guidelines for frontline and health workers to deal with and respond to anaphylaxis during the covid vaccine rollout. As per these guidelines health personnel trained in recognising anaphylactic symptoms and administering first aid had to be specifically stationed at all vaccination centres along with an adequate supply of anti-anaphylactic medicines.

The impact of anaphylaxis on the heart

According to Dr Naresh Kumar Goyal, director and HOD, cardiology and heart failure programme, Fortis Hospital Shalimar Bagh, New Delhi, “Anaphylaxis is a severe allergic reaction. Most commonly, it causes intense dilatation of blood vessels of the whole body, leading to shock and multi-organ dysfunction. It impacts the cardiovascular system in many ways. Usually, it leads to heart rate and rhythm disorder, increase or decrease heart rate or mild arrhythmias like atrial fibrillation (irregular rhythm in the upper chambers of the heart)”

Anaphylaxis activates the mast cell which releases the inflammatory markers known as cytokines in the body. These cytokines may cause spasms in coronary arteries – the blood vessels which supply nutrition to the heart which may lead to a reduction of blood flow to the heart.

Occasionally there is a rupture of plaque because of an intense allergic reaction which may lead to a heart attack known as kounis syndrome. It has its complications. Sometimes these cytokines attack heart muscles rather than blood vessels and cause heart failure which may lead to cardiogenic shock or sudden cardiac arrest because of conditions like ventricular tachycardia (irregular rhythm in the lower chambers of the heart).

What causes anaphylaxis?

The trigger for anaphylaxis could be anything from certain foods (especially in children) or medications to stings from bees, yellow jackets, wasps, hornets and fire ants.

Foods that cause anaphylaxis include peanuts and tree nuts, fish, shellfish, wheat, soy, sesame and milk. In adults, besides food, medications like antibiotics, aspirin, pain relievers and the intravenous (IV) contrast used in some imaging tests could be the trigger factors. Recurring episodes of anaphylaxis are often more severe than the previous ones. People with underlying health conditions especially heart-related ones are also at higher risk.

According to a review article in the Allergo Journal International, anaphylaxis accounts for more than 500 deaths annually. It is the most fatal and it is well known that the heart is directly and/or indirectly involved in severe human anaphylaxis. In conclusion, there is extensive experimental and clinical evidence that the human heart can be viewed as both a site and a target in anaphylaxis.

When an anaphylactic attack occurs, the heart is affected severely. Histamines, the substances released by the body during an allergic reaction, cause the blood vessels to expand, which in turn causes a dangerous drop in blood pressure. Fluid can leak into the lungs, causing swelling (pulmonary edema). Anaphylaxis can also cause heart rhythm disturbances.

What to do during anaphylaxis?

Experts say the immediate remedy is an injection of epinephrine after being rushed to the emergency room. “If not treated quickly, it could be fatal,” says Dr Nitin Jagasia, consultant emergency medical services, Apollo Hospitals, Navi Mumbai.


Anaphylaxis is a severe allergic reaction that could trigger extreme inflammation which could lead to heart failure. It had also emerged as a cause of worry during the pandemic due to some reports of isolated cases of people developing anaphylaxis after their covid shots.

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