Exercise as it relates to Disease/Arrhythmia in Athletes
 An arrhythmia is a problem with the rate or rhythm of the heartbeat. During an arrhythmia, the heart can beat too fast (tachycardia), too slow (bradycardia), or with an irregular rhythm (fibrillation).  It is believed that regular endurance athletes are inducing changes in their right ventricle, almost like a form of ventricular dysplasia (scar tissue on the heart). This may eventually lead to ventricular arrhythmia and sudden death. Furthermore, for individuals who already have underlying arrhythmia or other similar heart issues, it appears that with endurance exercise the risk is heightened even further.  Sinus bradycardia and AV block can frequently be observed in athletes, but they do not require attention as long as they are asymptomatic or do not produce pauses exceeding 4 seconds.
At the moment there is no conclusive study that can directly link intense exercise as a cause of arrhythmia, but there is enough cases to warrant concern. Particularly in individuals who have a family history of premature cardiovascular disease, it is recommended that they undergo ECG screening prior to undertaking physical activity.  Medical therapy includes beta blockers or antiarrhythmics, including sotalol, amiodarone, or others. Patients at high risk of sudden death may benefit from the protection of an implanted defibrillator .
•Prevent blood clots from forming to reduce stroke risk •Control your heart rate within a relatively normal range •Restore a normal heart rhythm, if possible •Treat heart disease/condition that may be causing arrhythmia •Reduce other risk factors for heart disease and stroke
Some recommended readings that help support this article http://bjsm.bmj.com/content/33/5/319.full.pdf+html
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2. Endurance athletes: exploring the limits andbeyond . 2013. Endurance athletes: exploring the limits andbeyond . [ONLINE] Available at: http://eurheartj.oxfordjournals.org/content/24/16/1469.. [Accessed 23 October 2013].
3. Stanford Cardiovascular Health - Stanford Hospital & Clinics - Stanford Medicine. 2013. Stanford Cardiovascular Health - Stanford Hospital & Clinics - Stanford Medicine. [ONLINE] Available at: http://stanfordhospital.org/cardiovascularhealth/. [Accessed 23 October 2013].
4. Electrocardiographic changes in 1000 highly trained junior elite athletes. . 2013. Electrocardiographic changes in 1000 highly trained junior elite athletes. . [ONLINE] Available at: http://bjsm.bmj.com/content/33/5/319.full.pdf+html. [Accessed 23 October 2013].Prevention & Treatment of Arrhythmia. 2013. 5. Prevention & Treatment of Arrhythmia. [ONLINE] Available at: http://www.heart.org/HEARTORG/Conditions/Arrhythmia/PreventionTreatmentofArrhythmia/Prevention-Treatment-of-Arrhythmia_UCM_002026_Article.jsp. [Accessed 23 October 2013].