Ventricular tachycardia (VT) is a fast arrhythmia (> 100/min) that originates in the right or left ventricle. The ventricles are the two chambers of the heart that receive blood from the atria. They contract in a synchronized way to send blood to the lungs (role of the right ventricle) or to other organs of the body (role of the left ventricle). An electrical impulse keeps the contractions from the upper chambers of the heart (atria) uniform and organized. Ventricular tachycardia occurs when the electrical impulse originates in the muscle of one of the two ventricles and not the atria. Ventricular contractions then become disorganized and inefficient, which compromises blood flow to the organs. Ventricular tachycardia is usually caused by abnormal muscle fibres, such as those resulting from an infarct scar, valve disease, a congenital (or birth) heart defect, or myocarditis (inflammation of the heart muscle). Some muscle problems are caused by genetic abnormalities such as hypertrophic cardiomyopathy, arrhythmogenic cardiomyopathy, and familial dilated cardiomyopathy. In these cases, a genetic abnormality is passed down from parents to a child or is caused by a new mutation of a gene. Ventricular tachycardia is one of the complications of these abnormalities.
Sometimes, ventricular tachycardia is not associated with any heart muscle abnormality. In these cases, the tachycardia may be caused by a genetic abnormality that is not associated with muscle weakness (cardiomyopathy), and the ventricular tachycardia is the only evidence of a genetic disease. Genetic abnormalities cause different syndromes (Brugada, long QT, short QT, catecholaminergic polymorphic ventricular tachycardia), which are all associated with ventricular tachycardia. Finally, some patients have ventricular tachycardia without evidence of a genetic disease or heart muscle disease. This is known as idiopathic ventricular tachycardia.
An infarct scar, a valve or congenital disease, or cardiomyopathy increases a person's risk of developing ventricular tachycardia. The family members of someone with genetic ventricular tachycardia are also at risk of having the same type of arrhythmia.
Tachycardia episodes may be very short (a few seconds) and symptomless.
Most patients who experience longer episodes (up to a few hours) may feel:
- Palpitations often accompanied by shortness of breath
- Chest pain (sometimes)
- Dizziness, if the tachycardia is particularly fast
- Syncope (fainting)
The severity of symptoms depends on the speed of the arrhythmia, its duration and the associated heart disease.
Ventricular tachycardia can also degenerate into another type of arrhythmia called ventricular fibrillation. This can lead to sudden death if not treated quickly.
A diagnosis is established with an electrocardiogram recorded during a ventricular tachycardia episode. Some patients require an electrophysiology study so that the arrhythmia can be identified. When a ventricular tachycardia diagnosis is established, other tests are conducted to determine the presence or absence of an associated heart disease.
- Echocardiogram
- Coronary angiography
- Cardiac magnetic resonance imaging
- High-resolution electrocardiogram
- Molecular genetic testing of a blood sample
- Holter monitoring
Depending on the severity of the problem and the associated heart disease determined by a medical evaluation and diagnostic tests, the doctor will recommend:
- Treatment for the underlying disease (coronary disease, valve disease, congenital disease)
- Drug treatment
- Implantation of a cardioverter defibrillator
- Catheter ablation of the ventricular tachycardia site of origin in the ventricle
- Surgery
- Family evaluation at the Genetics Centre