Exercise-induced tachycardia in elite athletes can be either benign or malignant. A normal response to exercise is an elevated sinus tachycardia and is perfectly safe. However, ventricular tachycardia is a malignant arrhythmia that can lead to death. According to a study published in the American Family Physician Journal, ventricular tachycardia is usually associated with an idiopathic hypertrophic cardiomyopathy, or abnormal thickening of the heart muscle. It is an arrhythmia that most athletes, including elite athletes, should be concerned about. Ventricular tachycardia can be brought on by exercise, taking stimulants or abnormal blood chemistry.
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What is Ventricular Tachycardia?
Ventricular tachycardia is an abnormally fast or rapid heart rate, usually over 150 beats per minute. It is a type of arrhythmia caused by problems with the heart's pacemaker or electrical system and can be brought on suddenly -- paroxysmal -- or have a slow onset -- non-paroxysmal. Ventricular tachycardia can be potentially life-threatening because it can lead to ventricular fibrillation, a severely abnormal heart arrhythmia, and sudden death.
An episode of ventricular tachycardia can have cardiac and non-cardiac causes and also can be exercise-induced. Cardiac causes include acute and chronic ischemic heart disease, valvular heart disease, mitral valve prolapse and cardiomyopathy, the most common cause in elite athletes. Stimulants such as caffeine, cocaine and alcohol can cause ventricular tachycardia, as can other drugs like psychotropics, antiarrythmics and sympathomimetics. Certain conditions and underlying diseases can also lead to tachycardia, such as abnormal potassium levels, excessive acid in the body fluids, abnormally low magnesium levels and an abnormally low level of oxygen in the blood.
Signs and Symptoms
People most often notice ventricular tachycardia when their heart rate is especially rapid or the episode lasts longer than a few seconds. Common symptoms include chest discomfort, fainting, fast heartbeat or palpitations, light-headedness, dizziness and shortness of breath. Typical signs are rapid or absent pulse, loss of consciousness and low to normal blood pressure.
Ventricular Tachycardia and Elite Athletes
A ventricular tachycardia diagnosis can be life-altering for an elite athlete, either forcing early retirement from a sport, as it did for triathlete Greg Welch, or requiring an implanted defibrillator to continue competing, as triathlete Emma Carney opted to do. In 2005, the 36th Bethesda Conference created recommendations for competition eligibility for athletes with ventricular tachycardia. Further evaluation of elite athletes is required, such as 12-lead ECGs, exercise testing, echocardiograms and cardiac catheterization. Experts recommend athletes with hypertrophic cardiomyopathy resulting in ventricular tachycardia be barred from competing in strenuous sports and suggest they participate in low-intensity sports such as bowling, golf, billiards or cricket. Elite athletes who have tried to compete in their sport while taking medications for their condition frequently complain of fatigue or diminished performance.