How ICDs Protect Against Sudden Cardiac Death: Lessons From Christian Eriksen’s Collapse
When Danish footballer Christian Eriksen collapsed during a recent friendly match, many viewers were startled to see him regain consciousness and walk off the pitch. The incident immediately revived memories of his on-field cardiac arrest during Euro 2020 in 2021, when his heart stopped and he required urgent resuscitation.
After that emergency, Eriksen received an implantable cardioverter-defibrillator (ICD), a small device designed to detect and treat dangerous heart rhythms. Following his latest scare, he reported that his ICD had acted as intended, saying it protected him when he needed it most. He is now recovering at home.
Doctors and heart charities have welcomed the positive outcome but caution that even the best devices cannot offer complete protection. ICDs can be highly effective at preventing sudden cardiac death, yet they do not cure the underlying heart condition. People with ICDs may still experience symptoms, blackouts and future medical complications.
What An ICD Actually Does
An implantable cardioverter-defibrillator is a small, battery-powered device, roughly the size of a large matchbox. It is placed under the skin, usually below the collarbone, and connected to the heart by one or more thin leads that pass through veins into the heart chambers.
The ICD continuously monitors every heartbeat, looking for signs of life-threatening rhythm disturbances such as ventricular tachycardia or ventricular fibrillation. These dangerous rhythms can prevent the heart from pumping enough blood to the body and brain, leading to collapse and, if untreated, cardiac arrest.
When the device detects a dangerous rhythm, it can respond within seconds. Depending on the specific pattern, it may first deliver a series of rapid pacing impulses to restore a normal heartbeat. If that fails, or if the rhythm is extremely unstable, the ICD can deliver a stronger electric shock to reset the heart.
Cardiologists often compare an ICD to an airbag in a car. It does not prevent the problem from occurring, but it stands ready in the background, providing critical protection when something goes badly wrong. Patients usually do not feel the device working unless a major shock is delivered.
Who Is Advised To Receive One?
ICDs are recommended for people who have survived a cardiac arrest or face a high risk of life-threatening heart rhythms. This group includes some patients with inherited heart disorders, such as long QT syndrome or hypertrophic cardiomyopathy, which can disrupt the heart’s electrical system.
They are also used in people with significant heart muscle damage after a major heart attack, or in those with cardiomyopathies that weaken the heart’s pumping function. When the heart is severely impaired, the risk of sudden arrhythmias rises sharply, and an ICD can significantly reduce the risk of sudden death.
International guidelines from major cardiology societies set out detailed criteria for ICD implantation. Doctors weigh the potential benefits against possible complications, as well as the patient’s overall health, age and preferences. For many people at elevated risk, ICDs have become a standard component of modern heart failure and arrhythmia care.
How An ICD Feels During An Event
When a dangerous rhythm develops, patients often experience warning symptoms such as palpitations, chest discomfort, shortness of breath or a feeling that they may faint. If the ICD delivers a high-energy shock, many describe it as a sudden kick or thump to the chest.
The shock can be painful and alarming, particularly the first time it occurs. However, it is specifically designed to stop a potentially fatal rhythm and restore normal circulation. For people who have already survived sudden cardiac arrest, the device is often viewed as a lifesaving safeguard.
Modern ICDs do more than deliver therapy. They also store detailed information about heart rhythms before, during and after each treated episode. Many newer models can transmit this data wirelessly to hospital monitoring systems, allowing cardiology teams to review events quickly and adjust treatment when necessary.
Why Blackouts Can Still Occur
Even with the rapid response of an ICD, there can be a brief period when blood flow to the brain falls. If a dangerous rhythm begins suddenly, a person may become dizzy or lose consciousness before the device has completed its analysis and delivered therapy.
Not every blackout in someone with an ICD is caused by a life-threatening arrhythmia. Other factors, including low blood pressure, dehydration, illness or overheating, can also cause fainting. This is especially relevant for athletes and highly active individuals, whose cardiovascular systems are already under significant strain during exercise.
Many ICD patients also take medications that slow the heart rate or lower blood pressure to reduce strain on the heart. While these medications are important, they can sometimes leave circulation less able to adapt to sudden changes in posture or intense exertion, contributing to lightheadedness or collapse.
Assessment After An ICD Shock
Whenever an ICD delivers a shock or records a serious arrhythmia, doctors aim to determine exactly what happened. The first step is often device interrogation using a specialized programmer, allowing specialists to download detailed information about heart rhythms and therapies delivered.
Doctors may also perform an electrocardiogram, blood tests and imaging studies such as echocardiography to assess heart function. These investigations help determine whether the shock was appropriate, whether new heart damage has occurred and whether medications or device settings require adjustment.
Clinicians also look for possible triggers, including missed medication doses, recent treatment changes, infections, electrolyte imbalances or increased physical and emotional stress. Addressing these factors may help reduce the risk of future episodes.
Special Challenges For Elite Athletes
Athletes such as Eriksen present particularly complex challenges for cardiology teams. Regular exercise is strongly recommended for most people with heart disease, but elite sport places the body under extraordinary physiological stress. Extremely high heart rates during competition can make it more difficult for an ICD to distinguish between normal exertion and dangerous arrhythmias.
In some individuals, intense exercise can itself increase the risk of arrhythmias, particularly when underlying heart scarring or inherited electrical disorders are present. For this reason, many professional organizations historically advised against high-level competitive sport for people with ICDs, although evidence in recent years has become more nuanced.
Eriksen’s successful return to Premier League and international football following his 2021 cardiac arrest demonstrated that, with careful evaluation and close monitoring, some athletes with ICDs can safely resume their careers. His latest collapse has renewed discussion about risk assessment, monitoring strategies and the balance between personal choice and medical caution.
Benefits, Limits And Everyday Life
ICDs have transformed survival prospects for many people at high risk of sudden cardiac death. Large studies have demonstrated significant reductions in mortality among selected patient groups, particularly those with severely weakened heart function following a heart attack or with specific inherited heart conditions.
At the same time, living with an ICD is not always straightforward. Some patients experience anxiety about potential shocks, restrictions on certain activities, and occasional device or lead complications that require additional procedures. Psychological support and clear information are often just as important as the technical aspects of treatment.
Eriksen’s collapse is a reminder that an ICD is only one component of comprehensive management for serious heart disease. These devices cannot eliminate underlying risk, but they provide a powerful safety net, allowing many people, including some professional athletes, to continue active and fulfilling lives while remaining under specialist care.
For the wider public, the incident also highlights broader lessons about cardiac emergencies. Rapid access to defibrillation, CPR training, widespread availability of automated external defibrillators and timely specialist care all play vital roles in improving survival after sudden cardiac arrest, both in elite sport and in everyday life.
