Sunday, 11 December 2011

The athlete's heart

As I lay in bed the other night I was more aware of my heart beat than normal. All athletes should at some point start learning to listen to their body as it talks to us in many ways. Muscle soreness tells us we have done a harder session or used muscles in ways we are not use to. Muscle pains warn us of impending, or if ignored announce, new injuries. Tiredness tells us we need rest and fever suggests we have some form of infective illness. Part of the monitoring process should include checking your resting pulse from time to time, ideally when you awake as this can warn you about whether your cold is more significant or whether your tiredness is perhaps starting to overreach your fitness.

What about if you are lying there and you become aware that your pulse is skipping beats or has become irregular? Should we be worried? What should we do? Well as I lay there I could feel a strong beat every third or fourth beat and then when I felt my pulse it was occasionally irregular. So I woke my wife up, she happens to be a doctor, and got her to check it and sure enough it was irregular. Half an hour later I had decided either I had some fatal heart arrhythmia or I had athlete's heart syndrome.

So what is "athlete's heart syndrome" (AHS) and what should you do about it? T

The most important distinction of AHS is that it is a diagnosis of exclusion, meaning you have to exclude more significant causes of heart problems, and that it is essentially benign, meaning that it is not associated with ill health or indeed sudden death which is pretty reassuring.

So what are the symptoms of athlete's heart syndrome?

Often there are no symptoms but features would include a slow heart rate (the bradycardia of fitness which most endurance athletes are aware of) such as exhibited by TdF cyclist Miguel Indurain who had a resting heart rate of 29 (which is definitely pathological in a non athlete). Other features might include occasional ectopic heart beats, leading to a slightly irregular pulse, but otherwise there is little else.

Where the problem comes is when you have either an ECG (electronic tracing of your heart rhythm, or an echocardiogram of you heart- an ultrasound scan of your heart which can look at how your heart functions).

What should you do if you have an irregular heart beat or other "unusual symptoms"?

1. See your doctor and get some tests

Firstly you should see you doctor and explain your symptoms: they should arrange some blood tests and a ECG. The blood tests are to exclude biochemical abnormalities such as a low a plasma potassium level, and other things that can cause problems such as an overactive thyroid which can cause arrythmias. They should also enquire about risks factors for arrythmias such as excess caffeine, alcohol, recreational drugs and fatigue all of which can induce abnormal heart rhythms. If you have had arrythmias then you should also have a 24 hr ECG and an echocardiogram.

2. The ECG, 24hr ECG and Echocardiogram

The ECG should be able to identify if you have a pathological heart rhythm, but here it gets difficult. Just like Miguel's heart rate being too slow for the untrained, fit people may have findings on their ECG that would be abnormal in an untrained person. So there is a grey area, and what if you only get the arrhythmia occasionally? If there is still concern then you can have a 24 hr ECG which essentially means having your heart monitored for 24 hrs and an echocardiogram to assess your heart function. The 24 hr ECG should identify if you have a significant risk of heart arrythmias but again should be interpreted with caution since some arrythmias are normal in the fit hea

3. What is a fit heart, why does it cause problems interpreting tests and who should I see?

As we train (say more than an hour a day) our heart gets fitter, which means amongst other things the muscle of our heart gets bigger. This occurs especially in the bit that does the most work, the left ventricle or LV for short. When the heart muscle gets bigger it becomes more efficient at pumping blood and is one of the reasons why at rest our heart rate becomes slower, as with each heart beat we can pump more blood around our body. Enlargement of our LV can be pathological and his is one of the key causes of sudden death and is therefore a cause for concern when it is seen on an ECHO study of you heart. It is very unlikely that an athlete who has been training for more than a year at a high level will have a pathological cause of LV enlargement. Where concern arises there are some subtle differences in the pattern of the echo changes between the fit heart and the abnormal heart, and perhaps the ultimate test is to detrain for a period of 1-3 months in which case if it is an athletic heart the LV enlargement should reverse. Where this does not occur it may be pathological (the condition is called HOCM) and would need further tests.

4. Should I be worried?

Sudden death in training athletes is very rare. Pathological findings are most common in those with less than a year of athletic training under their belt. In the older mid life crisis athlete (typically late thirties early forties with a history of little previous exercise and general poor lifestyle e.g. smoker etc) it is usually due to coronary artery disease resulting in a "heart attack". If you are this person and get chest discomfort on exercise you need to get a check up. In the younger athlete new to regular training
it is nearly always HOCM or occasionally a pathological heart rhythm. A family history may exist in which case you should have a screening test but unfortunately in some the first they know of it can be too late.

Happily for me my heart studies were completely normal, for an athletes heart, so I can continue training.

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