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Your heart rate is carefully controlled to respond to the needs of your body, increasing when you exercise, for example, before returning to a normal resting rate. Sometimes the system that controls your heart rate becomes abnormal and speeds up (tachycardia), slows down (bradycardia) or becomes irregular (arrhythmia). If the problem is in the main heart pump (the ventricles) rather than the atria, it can reduce the effectiveness of the pumping of blood.
Ventricular tachycardia (VT) refers to abnormally rapid beats originating from the lower chambers of the heart. If the heart rate is too fast, there is not enough time for new blood to enter the ventricle between contractions. VT occurs most often in patients with a weakened heart muscle, known as cardiomyopathy, or when scar tissue develops after a heart attack (myocardial infarction), but it can also occur in structurally normal hearts if the problem is primarily electrical. Certain drugs can also cause VT.
Symptoms of Ventricular Tachycardia
Often the symptoms of VT are mild, but if the heart rate during a ventricular tachycardia episode is very fast or lasts longer than a few seconds, several symptoms are often present:
- Chest discomfort (angina)
- Lightheadedness or dizziness that may result in fainting
- Awareness of your heartbeat (palpitations)
- Shortness of breath (dyspnea)
Certain forms of VT, particularly in the context of other coexisting heart diseases, can cause sudden cardiac death.
Diagnosing Ventricular Tachycardia
The diagnosis of VT requires an electrocardiogram (EKG), which measures the electrical activity of your heart. This needs to be done during the occurrence of VT. Because VT is episodic — it comes and goes — an EKG may not be able to catch it if the heart rhythm is normal at that particular time. Other tests may be required.
- A Holter monitor is a prolonged EKG recorded over a day or more
- An intracardiac electrophysiology study evaluates your heart's electrical circuits that control heart rate
- Blood tests identify possible medications or recreational drugs that may be accelerating your heart rate
Treating Ventricular Tachycardia
Some patients with VT may not need treatment at the time of diagnosis or ever; others may benefit from one of the antiarrhythmic medications available.
The definitive treatment for symptomatic long-term VT is an implantable cardioverter defibrillator (ICD), which is a device similar to a pacemaker that is implanted in the chest to normalize the heart rate.
A curative treatment is catheter ablation, a procedure in which doctors can find the areas where the VT is generated and destroy it with catheters inserted through the groin.