A mural in Copenhagen signed by fans in support of Eriksen, Image courtesy of the Associated Press

What Is an ICD and Why Did Danish Footballer Christian Eriksen Receive One After His Collapse?

A physician demystifies the event of a cardiac arrest and explains how it can be treated and even prevented.

Bo Stapler, MD
Science For Life
Published in
9 min readJun 22, 2021


“Damn it, I’m only 29 years old!” declared Christian Eriksen shortly after returning to consciousness. He awoke to find himself sprawled on a football pitch surrounded by concerned teammates and medical staff.

Seconds earlier the limp body of Denmark’s star midfielder had been subject to chest compressions, rescue breaths, and the electrical shock of a defibrillator in a desperate attempt to bring him back. Thousands at Parken stadium in Copenhagen and millions watching on television held their collective breath waiting for Eriksen to regain his.

A few minutes before halftime of Denmark’s Euro 2020 match against Finland on June 12th of 2021, Eriksen collapsed just as he attempted to field a ball coming towards him near the sideline. Team captain, Simon Kjaer, sprinted toward his fallen teammate and astutely helped keep Eriksen lying on his side. Maintaining such a position is beneficial when an unconscious person is still able to breathe as reports indicate was the case for Eriksen at the time. Remaining on his side rather than his back, served to prevent Eriksen’s tongue or other material like a mouthguard or vomit from obstructing his airway.

Denmark’s team doctor, Morten Boesen, recalled what happened next. “We were called onto the field when Christian collapsed. He was lying on his side when we approached him and there was respiration and pulse.” But just moments later, as Boesen described, “That picture changed.”

Footage of the television broadcast reveals medical staff initiating cardiopulmonary resuscitation (CPR) with chest compressions approximately two minutes after Eriksen’s initial collapse. CPR outside the hospital setting follows a simple algorithm as outlined in the figure below:

A summary of the American Heart Association’s Basic Life Support Algorithm, image by ACLS Medical Training, AED (Automated External Defibrillator), EMS (Emergency Medical Services)

Rescue breaths and chest compressions were administered once Eriksen was found to be breathless and without a pulse. Sticky pads attached to electrical wires were applied to Eriksen’s chest. These wires connected to a defibrillator. Compressions were paused for a moment so the defibrillator could detect any electrical signals coming from the heart of the young athlete.

Manikin attached to a defibrillator, image by James Rein at Pixabay

If the signals were consistent with a shockable rhythm — either ventricular fibrillation or ventricular tachycardia — as shown below, then a shock would be delivered by the defibrillator. As reports suggest, this was the case for Eriksen whose heart likely returned to a normal rhythm (3rd image below) after its disorganized electrical activity was reset by the shock. And yes, just like in the movies or on TV, the individual(s) operating the defibrillator would have yelled something like, ‘stand clear,’ before the device discharged so as not to shock anyone else at the scene.

Electrocardiogram (EKG) tracing of ventricular tachycardia, image from Amboss, creative commons
EKG tracing of ventricular fibrillation, image from Shutterstock
Normal Heart Rhythm (sinus rhythm) on an EKG, image from Wikimedia, creative commons

Eriksen had suffered from a cardiac arrest which is an often-deadly event that occurs when an individual’s heart either stops beating or contracts with such abnormal movements that it can no longer pump blood effectively enough to produce a pulse and deliver oxygen to vital organs like the brain.

The heart has four chambers. The top two are called the atria and contribute in a small portion to the heart’s overall pumping ability. The bottom chambers, called the ventricles, are larger and perform most of the work to pump blood to the lungs and other tissues of the body. The atria and ventricles normally contract in a coordinated fashion that allows blood to course through the heart and arteries smoothly and efficiently.

There are many medical conditions that could adversely affect the heart’s ability to conduct electrical signals, but whatever the underlying cause, something happened to Christian Eriksen during the match that caused his ventricles to contract abnormally. Perhaps they were beating very rapidly and inefficiently (ventricular tachycardia) or perhaps they were just quivering (ventricular fibrillation) as in the figure below. Either way, his heart was no longer able to supply his brain with enough oxygen to keep him conscious. If this had persisted for much longer, Eriksen could have suffered from permanent brain damage or even death.

Image from Anonymous at Makeagif

A cardiac arrest is not the same thing as a heart attack. From what can be gathered based on the limited information provided to the media about Eriksen’s health since his collapse, he did not suffer from a heart attack.

A heart attack, also called a myocardial infarction, is a sudden blockage of blood flow through the coronary arteries which are blood vessels lying on the outside of the heart (see above). The coronary arteries supply the muscle cells of the heart with oxygenated blood essential to maintain the life of these cells and fuel their high metabolic demand. When a plaque composed of platelets and cholesterol breaks off the wall of a coronary vessel and completely or partially obstructs blood from flowing through the artery, some of the muscle tissue in the heart can become damaged and even die.

If severe enough, or if left untreated, a heart attack can lead to a cardiac arrest, but there are also many other potential causes of cardiac arrest. Some of these are permanent conditions whereas others are considered reversible.

Common reversible causes of a cardiac arrest include electrolyte abnormalities like low or high potassium, calcium, phosphorus, or magnesium. Even though our electrolyte intake from food can vary from meal to meal, a healthy body tightly regulates levels of electrolytes in the blood by adjusting absorption in the intestines and output from the kidneys. Electrolyte disturbances are more likely to occur in patients with underlying health problems like chronic kidney or gastrointestinal disease, nutritional deficiencies, or as a side effect from medications.

Another set of conditions that could potentially lead to cardiac arrest include infectious diseases such as viral myocarditis. Covid-19 is one of the many viruses that can cause myocarditis, an inflammation of the heart muscle. Despite internet rumors that Eriksen’s cardiac arrest was related to the Covid vaccine, reliable sources have confirmed that he has neither received the vaccine nor suffered from a known Covid infection. In case you’re curious, the risk of myocarditis is significantly higher from a Covid infection than the vaccine.

Other reversible causes of cardiac arrest include the aforementioned heart attack as well as severe blood loss, a blood clot in the lungs, pneumonia, sepsis, adverse drug reactions or overdoses, chest trauma, and many other conditions that can be cured by medical or surgical treatment or will resolve on their own.

On the other hand, there are also a number of underlying conditions that could lead to cardiac arrest which are not reversible. These include abnormalities in the heart’s electrical conduction system such as prolonged QT syndrome and Brugada syndrome as well as valvular heart disease, or diseases of the heart muscle like hypertrophic, ischemic, or restrictive cardiomyopathy.

Footballers and other professional athletes often undergo pre-participation cardiac screening which involves tests such as electrocardiograms (EKGs) and echocardiograms designed to identify the irreversible heart conditions described above. Eriksen currently plays professionally with the Italian club, Inter Milan, but prior to his stent in Italy, he played for Tottenham Hotspur of the English Premier League.

Dr. Sanjay Sharma was Eriksen’s cardiologist during his time in Tottenham. Sharma commented the day after Eriksen’s collapse, “From the day we signed him, it was my job to screen him and we tested him every year. So certainly his tests up to 2019 were completely normal, with no obvious underlying cardiac fault.” Despite being highly reliable at identifying many heart conditions before they produce symptoms, these screening tests are not perfect, and sometimes underlying cardiac conditions are either missed or simply fail to manifest until some time after the testing is performed.

The outpouring of support for Christian Eriksen from those in the football community and the general public has impressed many, including Eriksen himself. After observing displays like the t-shirts worn by Russia and Finland prior to their match on June 16th and the wall of signatures penned on a mural in Copenhagen, Eriksen commented from his hospital bed on social media, “Hello everyone. Big thanks for your sweet and amazing greetings and messages from all around the world. It means a lot to me and my family.”

Photo of warmups prior to the Finland vs. Russia football match on 6/16, Image courtesy of Sportsstar

Some fans have taken a more practical approach to show support for Eriksen and raise awareness about cardiac arrest. Denmark has witnessed a seven-fold increase in the number of citizens registering for its Heartrunner app, a smartphone tool that alerts its users if there is a nearby individual in need of CPR so that assistance can arrive promptly.

Those who have experienced the trauma of a cardiac arrest while also having the good fortune to survive one, often undergo surgical placement of an implantable cardioverter-defibrillator, also known as an ICD. This device is like a mini defibrillator placed under the skin on the left chest. Thin wires connecting the ICD to the heart muscle allow the device to sense the heart’s rhythm and, in the event of an arrhythmia like ventricular tachycardia or fibrillation, deliver appropriate pacing signals or an electric shock to restore a normal rhythm. Because electrical pacing or a shock from an ICD can be initiated immediately after an arrhythmia occurs without having to wait for bystanders to provide and attach an external defibrillator, the victim is much more likely to survive a cardiac arrest.

Diagram of an ICD, image from Wikimedia, creative commons

Sometimes patients with a known cardiac disease that places them at high risk for a cardiac arrest, like congestive heart failure, for instance, undergo placement of an ICD even if they have never had an arrest in the past. This is referred to as primary prevention. As you might guess, when someone like Christian Eriksen, who has a history of cardiac arrest, receives an ICD it is considered secondary prevention.

ICD placement for secondary prevention is only recommended if the cause of a patient’s prior cardiac arrest is determined not to be reversible. So, it can be inferred that doctors have uncovered some irreversible etiology of Eriksen’s cardiac arrest which places him at increased risk for another arrest in the future. Irrespective of the underlying cause, by successfully undergoing ICD placement, Christian Eriksen, who was discharged from the hospital on June 18th, now carries both a better prognosis for his condition and the reassurance of a life-saving defibrillator with him at all times.

Will Christian Eriksen be able to return to professional football? It’s still too early to know at this point. However, playing with an ICD is not unprecedented. Daley Blind of the Netherlands played alongside Eriksen in Amsterdam from 2010–2013 and continues to play professionally for Ajax after receiving an ICD in 2019.

As I place my hand on my own chest and palpate impulses radiating from a heart that, for a few more than 29 years, has ceaselessly performed its task without me even noticing most of the time, I realize how Christian Eriksen’s story makes me appreciate the blessing of every beat. Football fans around the world, myself included, wish him the best as he continues to recover, and, regardless of whether or not he returns to the pitch, hope he is able to enjoy what some might consider his ‘second life’ to the fullest.

Dr. Stapler practices adult and pediatric hospital medicine in Billings, Montana, USA, and loves every minute of it (usually). Check out more of his work and follow him at bostapler.medium.com.



Bo Stapler, MD
Science For Life

Health & science writer on Elemental & other pubs. Hospitalist physician in internal medicine & pediatrics. Interpreter of medical jargon. bostapler.medium.com