Ventricular tachycardia (VT) is a type of irregular heartbeat that originates from the lower chambers of the heart (the ventricles). It is characterised by a rapid heart rate, typically greater than 100 beats per minute, and can be a potentially life-threatening condition.
VT can occur in people of all ages, but it is more common in those with underlying heart conditions, such as coronary artery disease, heart attacks, heart failure, or structural abnormalities of the heart. It can also be caused by certain medications or illicit drugs.
Characteristics
- P wave (if present) is not associated with a QRS
- Rhythm is Regular (usually)
- Rhythm is Fast (>100/Min)
- QRS is Wide (QRS > 0.12sec 3 small squares)
Ventricular tachycardia (VT) appears on an electrocardiogram (ECG) as a rapid and regular rhythm with a ventricular rate of more than 100 beats per minute. The QRS complex in VT is typically wide and abnormal, and may be symmetrical or asymmetrical.
In VT, the P waves may be absent or present but are usually not associated with the QRS complex. The QRS complex in VT can be either monomorphic (having the same shape) or polymorphic (having different shapes), and may be associated with a classic “heart-block” pattern, with a long PR interval and no visible P wave.
It is important to note that ECG findings can vary depending on the type and severity of the VT as well as individual patient factors.
Further key characteristics include:
- Rapid heart rate: Ventricular tachycardia is defined as a heart rate of more than 100 beats per minute.
- Origin: The abnormal heart rhythm originates from the ventricles, which are the lower chambers of the heart.
- Prolonged duration: Ventricular tachycardia can last for several seconds to several minutes, or even longer.
- Symptoms: Ventricular tachycardia can cause symptoms such as lightheadedness, dizziness, fainting, chest pain, and shortness of breath.
- Potentially dangerous: Ventricular tachycardia can be dangerous as it can lead to a cardiac arrest and death if left untreated.
Symptoms
Symptoms of VT may include:
- Palpitations: This may feel like a racing or fluttering sensation in the chest.
- Chest pain: This may be a sharp or crushing pain, or it may feel like pressure or tightness in the chest.
- Shortness of breath: This may be accompanied by a feeling of tightness in the chest.
- Lightheadedness or dizziness: These symptoms may be caused by a lack of oxygen due to the rapid heart rate.
- Fainting: In some cases, VT may cause a person to lose consciousness.
Pathophysiology
The pathophysiology of ventricular tachycardia is complex and involves several electrical and structural changes in the heart. Some of the key mechanisms involved in the development of ventricular tachycardia are:
- Abnormal electrical activity: Ventricular tachycardia is caused by abnormal electrical signals that trigger rapid and irregular contractions of the ventricles. This can occur due to reentry, triggered activity, or automaticity.
- Structural heart disease: Ventricular tachycardia is more common in individuals with underlying structural heart disease, such as heart failure, cardiomyopathy, or heart valve disease. These conditions can alter the normal electrical and mechanical function of the heart, leading to the development of ventricular tachycardia.
- Electrolyte imbalances: Electrolyte imbalances, such as low potassium or magnesium levels, can also contribute to the development of ventricular tachycardia.
- Certain medications: Certain medications, such as anti-arrhythmic drugs, can cause ventricular tachycardia as a side effect.
- Myocardial ischemia: Reduced blood flow to the heart muscle (myocardial ischemia) due to coronary artery disease or other conditions can also trigger ventricular tachycardia.
Overall, the pathophysiology of ventricular tachycardia involves a complex interplay of electrical, structural, and biochemical changes in the heart.
In some cases, VT may progress to ventricular fibrillation (VF), a more serious and potentially fatal arrhythmia.
Treatment for VT may include medications to slow the heart rate, electrical cardioversion to restore a normal heart rhythm, or implantation of a cardiac defibrillator to shock the heart back into a normal rhythm in the event of VF.