Ventricular tachycardia (VT or V-tach) is a type of abnormal heart rhythm, or
arrhythmia. It occurs when the lower chamber of the heart beats too fast to pump well and the body doesn't receive enough oxygenated blood. A normal heartbeat begins with an electrical impulse from the sinus node, a small area in the heart's right atrium (right upper chamber). Ventricular tachycardia begins in the lower chambers (ventricles) and is quite fast. When it lasts only a few seconds, ventricular tachycardia may cause no problems. But when sustained, ventricular tachycardia can lower the blood pressure, resulting in syncope (fainting) or lightheadedness. Ventricular tachycardia can also lead to ventricular fibrillation (a life-threatening arrhythmia) and cardiac arrest. What causes ventricular tachycardia?Structural Heart DiseaseVentricular tachycardia most often occurs when the heart muscle has been damaged and scar tissue creates abnormal electrical pathways in the ventricles. Causes include:
Idiopathic Ventricular TachycardiaSometimes, people with no known heart disease can develop ventricular tachycardia, often due to an irritable focus — when cells outside the sinus node start generating an electrical impulse automatically on their own. This form of ventricular tachycardia is easier to address and is usually not life threatening. Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT)Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a genetic condition that can cause a fast abnormal heart beat from the ventricles. CPVT may cause a loss of consciousness or sudden death due to the lack of blood pumped to the body. This inherited disease is common in individuals who have a family history of syncope, also known as fainting. What are the symptoms of ventricular tachycardia?When ventricular tachycardia lasts a short time, there may be no symptoms except palpitations — a fluttering in the chest. But ventricular tachycardia lasting more than 30 seconds may cause more severe symptoms:
How is ventricular tachycardia treated?
Learn more about arrhythmias or visit the Johns Hopkins Electrophysiology and Arrhythmia Service. Ventricular tachycardia refers to a wide QRS complex heart rhythm — that is, a QRS duration beyond 120 milliseconds — originating in the ventricles at a rate of greater than 100 beats per minute. This can be hemodynamically unstable, causing severe hypotension, and can thus be life-threatening. Ventricular fibrillation, asystole and sudden cardiac death can occur soon after ventricular tachycardia if action is not taken immediately. Ventricular tachycardia can occur with many variations of the QRS morphology, depending on where the arrhythmia originates, which sometimes makes diagnosis on ECG challenging. Below are two examples of ventricular tachycardia with different QRS morphologies — one with a right bundle branch block morphology and one with a left bundle branch block morphology. VT can also occur with QRS morphologies anywhere in between. You can find links to many more examples of VT at the bottom of this review. Ventricular tachycardia can be classified as sustained or non-sustained VT, or NSVT. Sustained VT is any ventricular tachycardia that lasts for more than 30 seconds or is symptomatic. Non-sustained VT lasts for less than 30 seconds and is asymptomatic. Ventricular tachycardia should be described by type (monomorphic or polymorphic), duration (sustained or non-sustained) and heart rate — i.e. monomorphic VT non-sustained at a heart rate of 220 bpm or sustained polymorphic VT at a heart rate of 250 bpm. Electrophysiologists may also describe the location within the ventricles from where the VT is originating. This can be determined by the morphology of the QRS complex. For example, VT that has a LBBB morphology must come somewhere from the right ventricle; this is because the electrical potential takes a long time to reach the left ventricle, similar to what occurs with a simple LBBB. Polymorphic VT (Torsades de Pointes) is a form of VT with multiple QRS morphologies. Polymorphic VT is best treated with intravenous magnesium. Patients with a prolonged QT interval have a higher risk for developing polymorphic VT. Removing offending drugs that prolong the QT interval and correcting potassium or calcium imbalances is crucial. Here is an example of polymorphic VT: Ventricular tachycardia can be difficult to distinguish from supraventricular tachycardia, or SVT, with aberrancy. The Brugada Criteria are most commonly used to differentiate between these two entities — a clinically important distinction. Similar rules are provided in the American College of Cardiology/American Heart Association Guidelines. If present, “fusion beats” and “capture beats” can also be helpful to diagnose VT. A fusion beat — also known as Dressler’s beat — occurs when sinus node activity (P wave) begins to conduct through the normal conduction pathway during an episode of VT. The abnormal ventricular impulse then conducts retrograde (backward) across the atrioventricular node, colliding with the sinus impulse. The resulting QRS is a fusion of the normal QRS morphology and the ventricular morphology from the VT. A capture beat is similar to a fusion beat, except the QRS morphology looks completely like the normal QRS complex, as the sinus node impulse conducts to the ventricles before the retrograde ventricular activation occurs. A few general rules apply to diagnosing ventricular tachycardia:
The Brugada criteria/algorithm is outlined below. 1. Do you see concordance present in the precordial leads (V1-V6)? Sometimes explained as the absence of a “RS complex,” concordance simply means “all up” or “all down.” A simple way to think of this would be to ask the question: Are all QRS complexes completely upright (positive) or completely downward (negative) in the precordial leads? If the answer is yes, then VT is the diagnosis. The images below show positive and negative concordance during VT. 2. Is the R to S interval greater than 100 ms in any one precordial lead? If the R to S interval exceeds 100 ms in any one precordial lead, then VT is the diagnosis. Simply use calipers to measure the distance between the R wave and S wave in each precordial lead. An example is below. 3. Do you see atrioventricular dissociation? If AV dissociation is present, the diagnosis is VT. AV dissociation occurs when P waves, representing atrial depolarization, are seen at different rates than the QRS complexes. This is present in only a small percentage of VT ECG tracings, but it is diagnostic of VT. Frequently, this is difficult to see due to the fast rate of the QRS complex. Below is an ECG strip of a patient with VT. See the PP interval when in sinus rhythm then march out the P waves within the wide QRS complex to find the AV dissociation that is present, confirming the diagnosis of VT. 4. Examine the morphology of the QRS complex to see if it meets the specific criteria for VT. VT is frequently either in a right bundle branch block (upright in V1) or a left bundle branch block pattern (downward in V1). If upward in lead V1 (RBBB pattern), then VT is present in the following situations:
If downward in lead V1 (LBBB pattern), then VT is present in the following situations:
Note that rhythms can, at times, originate in the ventricles but have a heart rate less than 100 bpm. These rhythms — called “idioventricular rhythms” — are sometimes referred to as “slow ventricular tachycardia” or “slow VT” because they meet the diagnostic criteria for VT, but the heart rate is below 100 bpm. When the heart rate is less than 60 bpm, and the rhythm originates in the ventricle, it is simply called an “idioventricular rhythm.” When the heart rate is between 60 and 100 bpm, it is referred to as an “accelerated idioventricular rhythm,” or AIVR; this is a common hemodynamically stable rhythm that occurs after myocardial infarction and requires no treatment. Some examples of both VT and idioventricular rhythms are below. ECG Examples:
References: Is ventricular tachycardia a SVT?Supraventricular tachycardia (SVT) is a condition where your heart suddenly beats much faster than normal. It's not usually serious, but some people may need treatment.
What is considered supraventricular tachycardia?Tachycardia means your heart is beating too fast. It can reach more than 100 beats a minute while resting. With SVT (supraventricular tachycardia), your fast heart rate begins in your upper heart chambers. The cause is a problem with the electrical signals and circuitry in the heart.
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Difference between supraventricular tachycardia and ventricular tachycardia
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