1) We sometimes read about marathon runners, athletes, and other fit, young individuals just dropping dead during or after a jog/run or a game. Common reason is cardiac arrest, heart attack or some kind of heart condition. Can you explain why this tends to happen to people who are more or less fit and healthy (and young), with no obvious health issues? 

People who appear and look healthy and fit does not necessarily imply that they have no underlying heart conditions.  The main reason for sudden cardiac death is often due to the development of a serious life-threatening abnormal rhythm of the heart known as ventricular fibrillation.  In this condition, the heart loses its pump function to deliver blood from the heart to the circulation of the body.  The heart muscles simply quiver instead of contracting.  This abnormal rhythm if left untreated will lead to cessation of heart beat called cardiac arrest and brain damage will ensue within 4 minutes and by 10 minutes brain death is almost certain.

There is significant myth and misconceptions that the cause of cardiac arrest in people who are athletes and marathons runners are due to heart attack.  There are different causes for sudden cardiac deaths in the young athletes and they differ from the middle-aged and older athletes.  The young athletes are defined as people below the age of 35 years and the older athletes include ages 35 and above.  For young athletes below the age of 35, a common cause of sudden cardiac death is not heat attack but congenital inherited conditions, the commonest being hypertrophic cardiomyopathy (33% of death occurs with this condition).  This is a condition where there is thickening of the muscles of the heart and also resultant fibrosis of the muscles of the heart, i.e. scarring of the heart.

Another inherit condition is called arrhythmogenic right ventricular dysplasia.  This condition is again due to scarring of the muscles of the right heart which can cause significant serious life-threatening abnormal rhythms when a person has extreme exercises.  Then there is a whole host of conditions called ion-channelopathies.  This is a condition where there is a defect or an imbalance of the electrolytes in particular sodium and potassium that maintains the electrical stability of the heart.

Finally there are also conditions called coronary ostial anomalies whereby the coronary arteries, i.e. the blood vessels that supply the heart are coming out from abnormal directions, from its usual sites, on the left and right side and may result in cut-off of blood supply during extreme physical activities.

These conditions are in contrast to sudden cardiac death in middle-aged and older athletes which are more related to heart attacks as well as a condition called myocarditis which is an infection of the muscles of the heart.  Please refer to my write-up for details on special issues on sudden death in the young.

As can be seen from the above, by just looking at athletes or marathon runners, one may not be able to access the existing underlying pathological heart conditions.

2) What are some of the signs of impending heart trouble while playing sports? At what point should you stop and seek medical advice? 

Warning symptoms and signs that may lead one to stop and to seek medical advice would obviously include the following:

1. Chest pain. I have listed a table of what constitute chest pain related to a heart problem as against chest pain which are atypical and are probably do not warrant medical treatment or advice.  See below.

How to recognize a heart attack : Chest Pain?

2. Unusual increasing shortness of breath during physical training or a marathon run that occurs earlier that the usual duration of physical activity
3. Giddiness associated with light-headedness; sensation of passing out
4. Excessive cold sweats especially related to the above: feeling nausea and abdominal discomfort/distension.
5. Irregular heartbeats or missed beats or palpitations that are apart from the normal exercise-induced acceleration of the heart rate.

3) Is there a way to tell if you are susceptible to these heart problems, since the attacks come without warning? Any genetic factors? Family history? Diet? 

Yes there are many ways to look at the possibility of a susceptible heart problem.  I have attached for your preview and importantly there is a questionnaire which is modified from the American Heart Association recommendations for pre-participation cardiovascular screening of competitive athletes.  People before embarking on high endurance sports and exercise may find this useful.

I have also listed some of the important conditions for sudden cardiac arrest.

4) These attacks while playing sports may be rare, but what advice can you give people who may be afraid to run take part in marathons, etc., because they worry they may be next? 

If somebody is interested in taking part in extreme sports but is afraid to do so because of concern of sudden cardiac arrest, the best thing to do is to see a doctor and to undergo a pre-participation screening program to certify themselves fit for such activities.  This will include consultation with a doctor focusing on detecting symptoms and signs of underlying heart conditions and also history of premature coronary artery disease and risks of sudden cardiac death in the family.  Cardiac testing which will usually include an electrocardiogram (ECG), exercise stress testing and heart imaging scans.  In addition one should not just take part in marathons without proper training.  This is mandatory as the heart needs to be physically conditioned to take on the physical strain involved in the marathon runs.

5) What advice can you give athletes who train a lot – are breaks important to rest the heart, how can you tell you are pushing yourself too far or exerting yourself?

There are 2 different forms of training that needs clarifications.  The first is cardiovascular fitness.  In this training program, one need not push oneself to the extreme.  Cardiovascular fitness is doing a form of exercise be it swimming, jogging or bicycling that push the heart rate to about 75 to 80 % of the maximum predicted heart rate of the particular person’s age and keep at this level of exercise for about 30 minutes.  A rule of thumb recommended by the Singapore Heart Foundation is a 3-5-7 routine – exercise 30 minutes a day, 5 times a week and up to a pulse rate of “170 minus age“ beats per minute.  The way to gauge this is to be able to converse in sentences with somebody next to you without having shortness of breath or taking gulps of air in between words.  Therefore the exercise would be enjoyable and very easily attainable.

In endurance exercise you will have to push much harder reaching the maximal heart rate and sustaining this level of heart rate for a longer period of time.  Clearly running at this level is meant for training for more extreme sports including marathon runs and playing competitive sports.

6) If you suffer an attack or cardiac arrest while playing sports, what are the chances you can be saved? 

A cardiac arrest that occurred during a marathon run or while playing sports is a medical emergency.  Time is of the essence because when the heart goes into fibrillation or stops, there will be a loss of blood supply to the brain and within 4 minutes, brain damage will star and by 10 minutes brain death is almost certain. Therefore it is mandatory that people around the victim should learn or should possess the skill of CPR, i.e. cardiopulmonary resuscitation which will be able to buy sometime for the ambulance medical service to arrive.  In most instances if there is an AED available, this should be applied to the victim and diagnosis made by the AED would prompt the bystander to deliver a shock to the heart, thus reverting the fibrillation, allowing the heart to re-set and to pump.

7) Do you think performance anxiety has anything to do with these attacks? Excess worry and anxiety over playing well, especially during competition, can put pressure on the heart, right? (As it might elevate stress levels?)

Performance anxiety is related to the activation and over-stimulation of the sympathetic nervous system. This is the nervous system that produces an increase in the blood adrenaline levels that allows a person to prepare to meet the task ahead.  Stimulation of the sympathetic nervous system increases the heart rate and also lowers the threshold for potential ventricular fibrillation if there any underlying heart conditions.  However this mechanism will also allow one to excel in competition and allow one to achieve greater competitiveness as well as endurance.