Ventricular tachycardia is a heart rhythm disorder (arrhythmia) caused by abnormal electrical signals in the lower chambers of the heart (ventricles).
Your heart rate is regulated by electrical signals sent across heart tissues. A healthy heart normally beats about 60 to 100 times a minute when at rest and is defined by signals that originate in the upper chambers of the heart (atria).
In ventricular tachycardia (V-tach or VT), abnormal electrical signals in the ventricles cause the heart to beat faster than normal, usually 100 or more beats a minute, out of sync with the upper chambers.
When that happens, your heart may not be able to pump enough blood to your body and lungs because the chambers are beating so fast or out of sync with each other that they don't have time to fill properly.
Ventricular tachycardia may be brief, lasting for only a few seconds, and perhaps not cause any symptoms. Or it can last for much longer and cause symptoms such as dizziness, lightheadedness, palpitations or even loss of consciousness.
In some cases, ventricular tachycardia can cause your heart to stop (sudden cardiac arrest), which is a life-threatening medical emergency. This condition usually occurs in people with other heart conditions, such as those who have had a previous heart attack or other structural heart disease (cardiomyopathy).
Ventricular fibrillation
A dangerous condition related to ventricular tachycardia is ventricular fibrillation (V-fib). In V-fib, your lower heart chambers contract in a very rapid and uncoordinated manner.
Sometimes this rhythm may occur as a result of ventricular tachycardia degenerating into ventricular fibrillation, or it may originate from single ventricular beats. This abnormal rhythm happens most often in people with established heart disease or a prior heart attack. It may also occur due to electrolyte abnormalities (such as high or low potassium levels) or, rarely, in otherwise normal hearts.
Ventricular fibrillation may also cause sudden cardiac arrest and lead to death if not treated immediately.
Brief episodes of ventricular tachycardia may not cause any symptoms in some people. Others may experience:
- Dizziness
- Shortness of breath
- Lightheadedness
- Feeling as if your heart is racing (palpitations)
- Chest pain (angina)
- Seizures
Sustained or more serious episodes of ventricular tachycardia may cause:
- Loss of consciousness or fainting
- Cardiac arrest (sudden death)
V-tach is caused by a disruption in the normal electrical impulses that control the rate of your ventricles' pumping action.
Many things can cause or contribute to problems with the heart's electrical system. These include:
- Lack of oxygen to the heart due to tissue damage from heart disease
- Abnormal electrical pathways in the heart present at birth (congenital heart conditions, including long QT syndrome)
- Structural heart disease (cardiomyopathy)
- Medication side effects
- An inflammatory disease affecting skin or other tissues (sarcoidosis)
- Abuse of recreational drugs, such as cocaine
- Imbalance of electrolytes, mineral-related substances necessary for conducting electrical impulses
In some cases, the exact cause of ventricular tachycardia can't be determined (idiopathic ventricular tachycardia).
The heart's electrical system
To understand the causes of heart rate or rhythm problems such as ventricular tachycardia, it helps to understand how the heart's internal electrical system works.
Your heart is made up of four chambers — two upper chambers (atria) and two lower chambers (ventricles). The rhythm of your heart is normally controlled by a natural pacemaker called the sinus node, which is located in the right atrium. The sinus node produces electrical impulses that normally start each heartbeat.
From the sinus node, electrical impulses travel across the atria, causing the atria muscles to contract and pump blood into the ventricles.
The electrical impulses then arrive at a cluster of cells called the atrioventricular (AV) node — usually the only pathway for signals to travel from the atria to the ventricles.
The AV node slows down the electrical signal before sending it to the ventricles. This slight delay allows the ventricles to fill with blood. When electrical impulses reach the muscles of the ventricles, they contract, causing them to pump blood either to the lungs or to the rest of the body.
When anything disrupts this complex system, it can cause the heart to beat too fast (tachycardia), too slow (bradycardia) or with an irregular rhythm.
Any condition that puts a strain on the heart or damages heart tissue can increase your risk of ventricular tachycardia. Lifestyle changes or medical treatment may decrease the risk associated with the following factors:
- Heart disease (for example, prior heart attack, hypertrophic cardiomyopathy, inflammatory diseases of the heart or genetic conditions)
- Use of recreational drugs
- Severe electrolyte abnormalities
- Medication side effects
Other risk factors
If you have a family history of ventricular tachycardia or other heart rhythm disorders, you may have an increased risk of ventricular tachycardia.
Complications of ventricular tachycardia vary in severity depending on such factors as the rate, and duration of a rapid heart rate, the frequency with which it happens, and the existence of other heart conditions. Possible complications include:
- Inability of the heart to pump enough blood (heart failure)
- Frequent fainting spells or unconsciousness
- Sudden death caused by cardiac arrest
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