Sudden Cardiac Death: Prevention and Screening – ACSEP Highlight

The wonderful Professor Kim Harmon presented at the ACSEP annual conference on the highly topical issue of sudden cardiac death in athletes. She outlined the issues in data collection that classically underestimates the prevalence of this devastating issue and discussed the management issues we face as a community. Here we summarise her presentation and add our own thoughts too.

Sudden cardiac death is a frightening thought. This phenomenon essentially refers to dying suddenly and unexpectedly due to heart problems with no significant warning symptoms. Many high profile cases have raised public awareness of sudden cardiac death. 2 prominent cases include the tragic deaths of Hank Gathers in the U.S. and of Marc Vivien-Foe whilst representing Cameroon in an international football match. Shock and alarm reverberates through society when an otherwise healthy professional athlete, who essentially is a symbol of optimum fitness and health, dies from sudden cardiac death during sport. Understandably a fear of exercise in the general public can then take grip. These responses are entirely natural and a media inquest usually begins. Was it a freak occurrence? Was it exercise that caused the death? Could it have been prevented? Are other athletes at risk? Am I at risk when I exercise?

All of these questions are important and relevant and create some difficult conundrums that the medical community have been trying to address for years. Despite the volume of research performed in sudden cardiac death, there is still some doubt in how aggressively this problem should be tackled.

One area where there is complete consensus in the medical community, is that the general public should be reassured that exercise is safe. These high profile cases attract significant media attention and can add an additional barrier to getting people moving and exercising. There is a small rise in risk of sudden cardiac death whilst exercising in all people but with regular exercise the overall risk of sudden cardiac death falls by approximately 40% and falls even further when considering all causes of death.

What Is The Risk Of Sudden Cardiac Death In Athletes?

The risk of sudden cardiac death is difficult to quantify accurately and varies considerably between different groups of athletes. Some studies have quoted incidences that range from 1 event per 35,000 athletes to as low as 1 event per 1 million athletes!

Much of the high-quality research has been performed in the U.S. in the college sports scene (NCAA). This group of young athletes have been interesting to study due to their age. We know SCD is more common in people older than 35 years old as this is when lifestyle-related disease (problems that occur because of poor health choices throughout life) such as coronary artery disease/atherosclerosis (blocked heart arteries) starts to kick in (this is what nearly killed Tony Butterfield recently who is a local Newcastle Knights Legend). However, the younger population should not have these lifestyle-related disease changes yet, as such their problems are usually congenital. This means they were born with the heart problem even if it hasn’t been an issue in their career as yet.

Coronary artery disease as a cause of sudden cardiac death
Coronary Artery Atherosclerosis

The overall risk of SCD in the NCAA athletes is approximately 1 in 50,000 with a much higher risk in males than females (5 to 10 times higher). People with African-American descent and Polynesians have a higher risk compared to caucasian ethnicity too (2-6 times the risk).

Sports that are high intensity and have a strength component tend to have higher risk as they place the cardiovascular system under higher stress. Basketball is consistently the sport with the highest risk (approx 1 in 9,000) versus football (soccer) for example where the risk is 1 in 24,000.

When the level of competition (professional vs amateur etc) was factored in, there was a significant change in SCD rates. This would be expected as at the higher echelons of all sports, the intensity is higher. In Division 1 NCAA basketball; the athletes’ risk was as high as 1 in 5000 per year. When this data was drilled into further, it was noted that there were a number of sudden cardiac arrests that occurred but did not result in the athlete dying (4 out of 5 survived due to rapid medical intervention with defibrillators which shows just how important it is to have medical personnel and defibs present at elite sports – Fabrice Muamba’s collapse and survival is an excellent example of this and well worth a read). Astonishingly there was 1 sudden cardiac arrest event per 1000 NCAA Division 1 athletes annually.

What Causes Sudden Cardiac Death?

In people older than 25, a large number of SCD is related to coronary artery disease. However, in younger patients this is a rare cause of SCD. Conditions that people are born with (congenital) are responsible for most deaths in young athletes but sometimes these conditions remain silent until a certain age. Some problems can be acquired during life too as a result of infection or systemic illness. All of the commonest causes of sudden cardiac death tend to trigger arrhythmias and cardiac arrest.

Variance in sudden cardiac death causes by region and activity
Variance in SCD causes by region and activity

Commonest Causes of Sudden Cardiac Death

Causes of sudden cardiac death are usually due to either structural problems with the heart or electrical conduction problems. Structual problems include abnormal arteries or abnormal size and shape of the chambers within the heart. Conduction problems result in irregular heart rhythms and can trigger ventricular fibrillation (cardiac arrest).

Hypertrophic cardiomyopathy as a cause of sudden cardiac death
  • Structural Problems With The Heart:
    • Hypertrophic cardiomyopathy (HCM)
    • Other cardiomyopathies (arrhythmogenic right ventricular dysfunction, dilated cardiomyopathy)
    • Coronary artery anomalies (different than normal anatomy of heart arteries)
    • Hole in the heart (Atrial or ventricular septal defects)
  • Electrical Conduction Problems With The Heart
    • Wolff-Parkinson White syndrome
    • Long QT syndrome
    • Brugada Syndrome
ECG showing hypertrophic cardiomyopathy
ECG showing hypertrophic cardiomyopathy

Cardiac Screening: For Everyone or Targeted To High Risk Groups?

I want to reinforce the message that for the vast majority of people, exercise is healthy and safe and the health benefits far outweigh any potential risk. For the general population, in the absence of known cardiovascular disease, metabolic disorders (such as diabetes) or kidney disease or symptoms of any of the above, exercise can be commenced at a low intensity and gradually increased safely – without the need for screening. Specific guidelines have been drawn up by the American College of Sports Medicine for assessing this and can be viewed below (click on the image).

ACSM pre-participation exercise screening guidelines

For athletes the questions is much more complex. Talking to your doctor and having a thorough examination will identify some causes of SCD, but it will also miss many others – in the medical field we refer to this as lots of ‘false negatives’. Essentially a normal examination does not mean you have no risk. Often SCD is the 1st sign of a problem, with only 18% of those who suffer sudden cardiac death having any symptoms prior to their death. So what else can be done?

The Role of the ECG in Cardiac Screening

What to expect during an ECG

The ECG tends to operate at the other end of the spectrum. So a normal ECG is very reassuring, especially in the presence of no symptoms and a normal examination (99% likelihood of having no problem). Unfortunately, ECG is what we call ‘very sensitive’. This means it can identify lots of ‘false positives’. Simply put, you may have a normal heart but an ECG may say otherwise. This is particularly true in young athletic populations (especially those under 16 years of age) and in Black athletes. As our understanding of Sports Cardiology has grown (International Criteria for ECG interpretation in athletes), we have managed to improve our understanding of normal variants in athletes and have reduced the number of ‘false positives’ identified. This is important as an abnormal test result has significant consequences including:

  • Unnecessary distress for the patient
  • Altered insurance eligibility or higher premiums
  • High expense of unnecessary investigations for people with no issue

These issues are of considerable concern given that as many as 1 in 300 youngsters will have something identifiable on ECG associated with increased risk of SCD, but even in NCAA athletes, the risk of SCD is only 1 in 50,000.

ECG Sensitivity and Specificity for detecting

Cardiac Screening for Sudden Cardiac Death Causes

This discrepancy in ECG ‘positives’ and actual rates of SCD is why screening is not supported in the general population. However, the Australasian College of Sport and Exercise Physicians does recommend selective screening in young elite athletes (16 to 25 years old) every 2 years and a cardiac screen for people older than 25 years on entering an elite program.

In U.S. soccer there is a significant cardiac screening program in play. Despite this, the incidence of SCD is 1:15,000. An adverse finding on screening doesn’t mean the athlete MUST stop sport, but they need to be appropriately counseled on the risk of sudden cardiac death if they continue with certain sports. In one review, 5 athletes were found to have had hypertrophic cardiomyopathy (a common structural cause of SCD). After medical advice, 3 athletes stopped playing and all survived. 2 athletes chose to continue playing. Tragically, both athletes died.

Cardiac Screening at Newcastle Sports Medicine

If you would like to have a cardiac screen performed, this can be completed by Dr Cairns. Dr Cairns frequently screens elite athletes and is able to assess for multiple issues such as SCD, undiagnosed respiratory issues, nutritional problems such as iron deficiency as well as musculoskeletal and biomechanical problems. To make an appointment call (02) 4910 0805.

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