Exercise as it relates to Disease/Exercise-induced ventricular tachycardia

What is Ventricular Tachycardia?
Ventricular tachycardia is a type of arrhythmia defined by a series of three or more consecutive heart beats arising below the atrioventricular node at a rate of between 100 and 250 beats per minute (bpm). It is the most commonly occurring life-threatening arrhythmia and is known to become increasingly prevalent with age. A higher risk of ventricular tachycardia exists among the following populations:
 * People with conditions that may affect heart disease, such as hypertension or diabetes
 * People with a family history of sudden cardiac death or coronary artery disease
 * Smokers
 * Alcoholics
 * People who have previously experienced heart disease

Types of Ventricular Tachycardia
Ventricular tachycardia can be classified as either sustained (occurring for more than 30 seconds) or non-sustained (occurring for less than 30 seconds). The condition is often found in patients with underlying structural heart diseases, such as myocarditis, congenital heart disease and myocardial ischemia. However, around ten percent of all cases of ventricular tachycardia occur in patients with structurally normal hearts and no underlying disease. In this instance, the condition is referred to as idiopathic.

Ventricular Tachycardia and Exercise
For sufferers of ventricular tachycardia, exercise may be a trigger of the condition. In many cases, exercise-induced ventricular tachycardia leads to the discovery of an underlying structural heart condition. However, the occurrence of idiopathic ventricular tachycardia during exercise is also common. Often, ventricular tachycardia will occur during the recovery period post exercise due to increased levels of adrenaline. In a study conducted in 1991, it was found that 70% of patients tested experienced idiopathic ventricular tachycardia as a result of exercise. A similar study found that exercise initiated ventricular tachycardia in 80% of idiopathic patients and 80% of patients with coronary artery disease.

Research identifies that there may also be a link between endurance exercise and the prevalence of ventricular tachycardia. It has been suggested that athletes undergoing continuous and excessively strenuous training may have a weakened heart, predisposing them to a decrease in cardiac function. As a result, left ventricular function may also be decreased and the risk of ventricular tachycardia amplified. Research shows that a heightened vagal tone may also contribute to athletes experiencing bouts of ventricular tachycardia. Greg Welch and Emma Carney, both triathletes, are examples of high level endurance athletes who have had their careers cut short by exercise-induced ventricular tachycardia.

Symptoms
Symptoms experienced by patients with both sustained and non-sustained ventricular tachycardia may include:


 * Palpitations
 * Breathlessness
 * Light-headedness
 * Vertigo
 * Dizziness
 * Angina
 * Syncope

However, ventricular tachycardia patients may also be asymptomatic.

Prognosis and Recommendations
The prognosis for patients with ventricular tachycardia is largely dependent on whether or not there is an underlying structural heart condition. For idiopathic patients, ventricular tachycardia induced by exercise may be recurrent but ultimately has a good prognosis. However, patients with a heart condition may be at a higher risk of ventricular fibrillation, an uncoordinated contraction of the heart resulting in cardiac arrest.

When symptoms of ventricular tachycardia present, it is highly recommended that the patient be transferred to hospital immediately, where they will undergo an electrocardiogram (ECG) to confirm the diagnosis. Upon diagnosis of ventricular tachycardia, patients generally undergo further investigation for any structural heart diseases. Treatment of ventricular tachycardia varies depending on the results of this investigation; however, various lifestyle changes are often recommended to all patients. These include discontinuing smoking, avoidance of excessive drug and alcohol use as well as dietary modification. Use of an implantable cardiac defibrillator (ICD) is also common amongst patients with ventricular tachycardia. An ICD is a small, electronic device placed in the chest that detects any abnormal heart rhythm, such as that experienced during ventricular tachycardia. The ICD returns the heart to normal rhythm either by tuning the heart beat to a programmed rhythm or electrically shocking the heart. Another treatment commonly used is radiofrequency ablation, a procedure in which abnormal tissue is destroyed by heat generated from a high-frequency current. Radiofrequency ablation produces a cure rate of around 90% in patients with idiopathic ventricular tachycardia.

Patients with ventricular tachycardia are often restricted from participating in exercise of moderate to high intensity; however, controlled levels of exercise can be maintained following medical consultation. It has been found that the risk of ventricular tachycardia decreases with deconditioning, which in turn may decrease the risk of sudden cardiac death. For this reason, athletes with the condition are generally no longer able to compete at a high level and may be forced to retire from competitive sport.