MBBS (Hons), MD, FRACP, FACC, FCSANZ
Director, Cardiac Electrophysiology Laboratory, St. Vincent’s Hospital, Sydney
In 2009, a woman pleaded guilty to reckless homicide and faces up to five years in prison for exercising her husband to death in a swimming pool. He suffered a ‘heart attack.’  We cannot know, however, whether this was an ischaemic event or an arrhythmia. Exercise is promoted and encouraged in society; it is considered a healthy pursuit with benefits to the heart and mind. We know that certain heart diseases make exercising dangerous, but what risk is exercise to a healthy person without known heart disease?
Ancient history records the death of the Greek messenger Phidippides who ran 26 miles from Marathon to Athens to deliver the news of the victory over Persian invaders, only to collapse and die soon after his arrival.
In the past few years we have heard of professional athletes collapsing during soccer and basketball games and on the athletics track. These are graphically represented and frequently viewed on YouTube. In September last year, Evander Sno, a midfielder for Dutch soccer giants, Ajax, suffered a cardiac arrest during a match. He was successfully resuscitated after four shocks from an external defibrillator – an outcome unfortunately not shared by several athletes in recent years.
Not so long ago, there was evidence to suggest that marathon runners were immune to coronary artery disease,  and this idea has pervaded public perception. If someone can compete in countless marathons and triathlons, how could they possibly be at risk of dying from a heart attack? This has been debunked however, with the finding that coronary disease is the major cause of exercise related deaths in the over 35 age group; a phenomenon also seen in younger individuals.  To confuse matters more, there is evidence that strenuous activity kills patients with known heart disease but the risk is reduced if they exercise on a regular basis compared with those who are sedentary.  To top it off, recent Australian research shows evidence of damage to the right ventricle detected by MRI following a triathlon in normal hearts. 
One of the problems in identifying athletes at risk is the similar appearances of the athletic heart to abnormal pathological hearts. Physiologic changes can occur which mimic the appearance of these conditions (so-called ‘athlete’s heart’). They can manifest as morphologic changes (such as wall thickening mimicking hypertrophic cardiomyopathy), ECG changes (usually voltage changes, non-specific…