David Nunan, programme Director for the PGCert in Teaching Evidence-Based Health Care, writes with Evidence-Based Healthcare MSc student Aaron Lear, Akron General Orthopedics, Cleveland Clinic.
The footage of Denmark’s midfielder Christian Eriksen collapsing on the pitch and receiving treatment was shocking. The professionalism of the medical staff meant there was thankful relief at the end of an emotional night in Copenhagen.
Within 24 hours Denmark’s team doctor revealed Erisken suffered a heart attack which caused him to collapse. At some point, his heart also stopped — medically referred to as a cardiac arrest. The only way to restart the heart is to apply an electric shock to it using a defibrillator. This is why the team doctor proclaimed “He was gone”.
Many questions remain unanswered. What was the underlying cause of Eriksen’s collapse? How can this happen to a player at the highest level of football? Perhaps most importantly, can we stop this from happening again? The science will likely provide a clear answer as to the cause but it isn’t so clear on how we prevent such cases in the future.
Why did a young and fit sports person suddenly collapse?
The cause of Eriksen’s collapse has yet to be reported, but it is unusual for a 29-year-old to suffer a typical heart attack (due to a blocked artery for example). More common in these situations is for the heart to go into an abnormal rhythm, which can lead to a sudden cardiac arrest. Causes of abnormal rhythms include underlying genetic conditions that affect heart muscle growth, such as cardiomyopathy, or the heart’s electrical system such as long QT syndrome; or congenital abnormalities of the coronary arteries disrupting blood flow. Inflammation of the heart muscle can also be a cause and can occur after a recent infection. Sometimes the cause remains unknown; a study of American athletes was unable to identify a cause in 37% of cases of sudden cardiac arrest due to a lack of records.
The heart muscle can also change in size and function due to prolonged, vigorous exercise, which can lead to changes to its electrical and chemical activities. There is debate as to whether these adaptations lead to abnormal rhythms and cardiac arrest but the consensus is these are healthy adaptations and do not present a risk. This position may change as the true volume of unexplained cardiac arrest in sport becomes clearer.
How common is what happened to Eriksen?
Good estimates as to how frequently young athletes collapse due to sudden cardiac arrest, and how many of these unfortunately die, are difficult to determine and vary widely. We recently published a systematic review assessing evidence for how often sudden cardiac death and arrest occurs in young athletes and military members. We identified high-quality evidence that each year around 2 to 5 out of every 100,000 competitive athletes aged 14 to 25 years old are likely to suffer sudden cardiac death. This risk goes up when considering only males, and increases further still in black males. High-quality evidence of cardiac arrest was too few to be reported with confidence.
How often does this occur in football players? Again the evidence varies, but estimates from one high-quality study on mostly male teenage footballers in the English Football Association put the numbers of sudden cardiac deaths between 3 to 14 for every 100,000 players annually.
For perspective, we would expect between 50 to 100 cases of cardiac death per 100,000 people in the general population over one year.
Why was Eriksen’s condition missed?
Athletes at many levels routinely undergo preparticipation evaluations which typically include questions about previous heart symptoms or events and a physical assessment including a doctor listening to the heart. At more advanced levels of sport, electrocardiogram (ECG) and ultrasound scans might be added to these examinations to identify cardiac abnormalities which might lead to cardiac arrest. While the details in Eriksen’s case have not yet been reported, it has been stated that he passed his medicals with his current teams.
Part of the problem is that many of the normal adaptations to the athlete's heart can overlap with some of the causes of abnormal rhythms, including cardiomyopathies that would be of concern in non-athletes. This can lead to incorrectly diagnosing a problem that doesn’t exist or is unlikely to lead to a serious event. The term for when this occurs is a false-positive finding. The overlap between the electrical manifestations of cardiomyopathies and athletic training has a false-positive rate of 9% to 25% for ECGs, meaning as many as 25 out of 100 athletes who undergo ECG testing could be falsely diagnosed with a serious heart condition.
The other issue is that abnormalities can be intermittent and potentially missed by the ECG heart traces and ultrasound scans. Assessments falsely interpreted as normal when there is an underlying condition are known as false negatives.
Can we prevent another Eriksen?
Preparticipation examinations act as screening to identify those at risk of a serious event and prevent it from happening. It might surprise you to know the evidence to support this claim is not clear cut.
Some evidence for the efficacy of ECG-based screening in reducing sudden cardiac death comes from a large prospective Italian study that started after a move to require ECG screening for athletic participation. Over a 25-year period, the study found that ECG screening in athletes reduced the incidence of sudden cardiac death by 90%. Other similar studies have not found a benefit of ECG-based screening.
The problem is these studies were not properly designed to assess the impact of ECG-based screening for preventing sudden cardiac death in athletes. To do this we need to compare death rates in young athletes who undergo screening with a control group of unscreened athletes from the same population. Ideally, athletes should be allocated to screening or no screening at random to prevent biasing the results.
In a second study, we looked to see if these types of studies had been conducted and what they found. The first finding was there were only a few such studies — 4 in total. When we combined the data from two studies in 3,869,274 participants, we found an inconclusive 42% relative decrease in risk of sudden cardiac death in athletes who were screened equating to an absolute risk reduction of 0.0016%. Another way to express this is we would need to screen 625 athletes to prevent one of them from sudden cardiac death. There was a lot of uncertainty in our data, with findings also indicating the potential for an increased risk of sudden cardiac death in the athletes who were screened. None of the studies we found randomly assigned participants to screening or no screening meaning we have less confidence in the findings. Evidence for the role of ECG-based screening to prevent sudden cardiac death remains very uncertain.
There is difficulty in gathering good evidence here. Asking athletes to participate in a study where they might be falsely disqualified from participating in their sport, with the potential emotional, psychological and financial implications, is a hard ask. Add in the issue of false-negative findings and the need for professionals skilled in interpreting athlete screening tests means the current approach to the cardiac screening of young athletes is that it should be voluntary and not mandatory.
Early defibrillation saves lives
In the case of cardiac arrest in athletes, acknowledging this occurs and being prepared for it when it does is probably the best strategy we have to save lives. Being prepared includes quickly recognizing a cardiac arrest compared to a routine injury, having coaching and medical staff available who are trained in cardiopulmonary resuscitation (CPR), and the availability of automated external defibrillators (AEDs) for rapid deployment when called for. Research from the US suggests that approximately 50% or more of athletes suffering cardiac arrest survive. This likely corresponds to the wide availability of AEDs and personnel trained to respond to these incidents being onsite.
Eriksen’s case has also raised awareness of the importance of early intervention in sudden cardiac arrest in the general public. Such discussions are vital given that the rate of survival in members of the public drops to around 10% and is likely due to a lack of early CPR and the availability of an AED.
About the authors:
David Nunan - Director of the PGCert in Teaching Evidence-Based Health Care
Aaron Lear - MSc in EBHC student, Akron General Orthopedics, Cleveland Clinic