--- title: Ventricular tachycardia and sudden cardiac death description: What ventricular tachycardia is, why it can cause sudden cardiac arrest, how it is detected, which treatment and prevention approaches clinical guidelines describe and when urgent help is needed. type: disease preset: ventricular-tachycardia aliases: - VT - SCD - ventricular arrhythmias sources: - tier: guideline org: minzdrav-rf title: Желудочковые нарушения ритма сердца. Внезапная сердечная смерть year: 2025 doi: 10.15829/1560-4071-2025-6670 url: https://cr.minzdrav.gov.ru/view-cr/569_2 - tier: reference org: msd-manuals title: Ventricular Tachycardia (VT) year: 2024 url: https://www.msdmanuals.com/professional/cardiovascular-disorders/specific-cardiac-arrhythmias/ventricular-tachycardia-vt - tier: reference org: msd-manuals title: Ventricular Tachycardia (Consumer Version) year: 2025 url: https://www.msdmanuals.com/home/heart-and-blood-vessel-disorders/abnormal-heart-rhythms/ventricular-tachycardia - tier: reference org: msd-manuals title: Cardiac Arrest year: 2025 url: https://www.msdmanuals.com/professional/critical-care-medicine/cardiac-arrest-and-cpr/cardiac-arrest - tier: guideline org: nice title: Implantable cardioverter defibrillators and cardiac resynchronisation therapy for arrhythmias and heart failure (TA314) year: 2014 url: https://www.nice.org.uk/guidance/ta314 - tier: guideline org: nice title: Transient loss of consciousness ('blackouts') in over 16s (CG109) year: 2023 url: https://www.nice.org.uk/guidance/cg109 - tier: textbook title: Anatomy and Physiology 2e (OpenStax), Chapter 19.2 Cardiac Muscle and Electrical Activity year: 2022 isbn: 9781711494067 url: https://openstax.org/books/anatomy-and-physiology-2e/pages/19-2-cardiac-muscle-and-electrical-activity sources_checked: 2026-10-12 review: null --- Ventricular tachycardia (VT) is a rhythm disorder in which fast beats are triggered not by the sinus node but by the ventricles: below the bundle of His, in its branches, the Purkinje fibres or the ventricular muscle. The Russian Ministry of Health guideline defines VT as three or more consecutive beats arising from the ventricles at a rate of more than 100 per minute. VT is dangerous because it can turn into ventricular fibrillation, a form of cardiac arrest. How the impulse normally travels through the heart is explained in the article on the [conduction system of the heart](../../anatomy/conduction-system/). Sudden death is an unexpected death, not caused by injury, within an hour of the onset of symptoms in a person who seemed healthy; it is called sudden cardiac death (SCD) when its most likely cause is heart disease or a rhythm disorder. SCD accounts for about half of all deaths from cardiovascular disease, in half of cases it is the first sign of disease, and its most common mechanism is a ventricular tachyarrhythmia.

Normally every heartbeat is started by an impulse from the sinus node in the right atrium. The ventricles are activated by the impulse that comes from the atria through the atrioventricular (AV) node.

In VT the fast beats start in the ventricles themselves, independently of the atria and the AV node. The diagram shows a common mechanism in people with a scar in the ventricular wall: the impulse travels round a re-entry circuit in the scar zone, and the narrow part of this circuit is called the critical isthmus. The circuit activates the ventricles again and again, so the rhythm is fast and regular and the QRS complexes on the ECG look identical (monomorphic VT).

## Why it happens Most often VT occurs in people with a serious heart condition: coronary heart disease, especially when a heart attack has left a scar in the heart muscle, inflammation of the heart muscle, or a cardiomyopathy. In damaged muscle there are areas where the impulse is conducted more slowly, and the impulse can start travelling round in a circle in the scar zone. An episode can be triggered by low potassium or magnesium in the blood, lack of oxygen, too much acid in the blood, reduced blood supply to the heart muscle (ischaemia), fever and side effects of some medicines. Less often VT occurs in young people without an obvious heart condition, for example in inherited disorders of the heart's ion channels (channelopathies), which include [long QT syndrome](../long-qt-syndrome/). The main mechanisms of ventricular arrhythmias are re-entry, abnormal automaticity, triggered activity due to early or delayed afterdepolarisations, and enhanced normal automaticity. In patients with LV dysfunction and sustained VT the mechanism is in many cases a re-entry circuit related to scar, and such VT is most often monomorphic. Non-sustained VT lasts less than 30 seconds and stops spontaneously; sustained VT lasts 30 seconds or longer or needs intervention to terminate it; in monomorphic VT the QRS complexes are identical (a single focus or re-entrant pathway), in polymorphic VT their configuration varies. Torsades de pointes is a subtype of polymorphic VT associated with QT prolongation. Without an evident structural heart disorder there are idiopathic outflow tract VTs and ventricular arrhythmias in channelopathies: long QT syndrome, Brugada syndrome, catecholaminergic polymorphic VT and short QT syndrome. ## Symptoms What people feel varies a lot: from no symptoms at all to palpitations, chest discomfort or pain, breathlessness, dizziness, feeling faint and fainting. During a long episode the ventricles cannot fill adequately or pump blood normally, so blood pressure falls. Palpitations, feeling faint and fainting are the three most important symptoms that need a visit to a doctor and further tests. In cardiac arrest the person collapses suddenly, without warning, sometimes with brief jerking movements; they are unconscious, not breathing and have no pulse. VT of short duration or slow rate may be asymptomatic, whereas sustained VT is almost always symptomatic, causing palpitations, symptoms of haemodynamic compromise or sudden cardiac death. Sudden cardiac arrest is an unexpected cessation of circulation within an hour of the onset of acute symptoms that was reversed by successful resuscitation (for example, defibrillation). Cardiac arrest is diagnosed clinically by unconsciousness, apnoea and pulselessness. ## How it is diagnosed The main tests are the [electrocardiogram](../../diagnostic/ecg/) (ECG) and [Holter monitoring](../../diagnostic/holter-monitoring/). ECGs recorded during a rhythm disturbance are especially valuable: keep them and show them to your doctor. If rare fainting episodes cannot be recorded, an implantable heart rhythm monitor may be needed. Echocardiography (heart ultrasound) is recommended for everyone with suspected or confirmed VT: it shows how the ventricles work and whether there is heart disease. If echocardiography does not give a clear answer, a cardiac MRI or CT scan may be done. Blood tests for potassium and magnesium help find causes that can be corrected. The doctor will ask whether any relatives died suddenly and unexpectedly at a young age, for example by drowning. If a post-mortem found no clear cause of a sudden death, the person's close relatives should be told about their possible risk and be examined by a cardiologist. ECG features common to all ventricular arrhythmias are a wide, abnormal QRS complex (≥ 120 ms), no preceding P wave, a T wave discordant to the main deflection of the QRS complex, and fusion complexes. Any wide QRS complex tachycardia should be considered VT until proved otherwise; concluding that it is supraventricular only because the patient is haemodynamically stable is a common mistake. In all adults with VT, transient factors are looked for: use of cardiac glycosides and antiarrhythmic drugs, serum potassium and magnesium, signs of acute myocardial infarction, and hyperthyroidism. In about half of cases an inherited arrhythmic disease, mostly a channelopathy, is found in relatives of SCD victims. The guideline does not recommend ECG screening of the general population. ## How it is treated If VT compromises the circulation — blood pressure falls, the person faints or nearly faints, there are signs of acute ischaemia of the heart muscle or fluid on the lungs — the rhythm is urgently restored with an electric shock (electrical cardioversion). Even when the person is stable, a long (sustained) episode of VT is stopped straight away because their condition can worsen quickly; this is done with a shock, antiarrhythmic medicines or electrical pacing of the heart. Short episodes usually do not need urgent treatment unless they are frequent or long enough to cause symptoms. The main long-term goal is to prevent sudden death rather than simply to suppress the arrhythmia. The basis is treating the heart condition that caused VT, above all coronary heart disease. The main means of preventing sudden death is an implantable cardioverter defibrillator (ICD): a small, battery-powered device implanted under the skin just below the collarbone, with leads (tiny wires) inserted into the heart. The ICD monitors the heart rhythm and stops a dangerous arrhythmia with a painless burst of electrical pulses or with a shock. It is usually implanted under local anaesthetic. Catheter ablation is a procedure in which a special catheter is passed through the blood vessels into the heart and energy is delivered to an area of heart muscle to eliminate the arrhythmia. Antiarrhythmic medicines are an additional treatment: each carries a considerable risk of side effects, including causing rhythm disturbances themselves. The doctor and the patient decide together which approach to take. People with an ICD need to have the device checked by their doctor as scheduled; under the Russian guideline they must not drive for the first 3 months after implantation and for 3 months after the ICD has fired to treat a genuine arrhythmia (an appropriate therapy). Emergency electrical cardioversion is recommended for VT with acute haemodynamic compromise: symptomatic hypotension, syncope or presyncope, signs of acute myocardial ischaemia, pulmonary oedema or acute heart failure. In sudden cardiac arrest (pulseless VT or VF), immediate cardiopulmonary resuscitation is required, and its key element is emergency defibrillation. Sustained monomorphic VT is terminated immediately even when haemodynamically stable — by cardioversion, antiarrhythmic drugs or pacing; all antiarrhythmic drugs can cause hypotension, and cardioversion is not indicated for recurrent non-sustained VT. Apart from beta-blockers, no antiarrhythmic drug has been shown to reduce all-cause mortality. The ICD is the main means of primary and secondary prevention of SCD. For secondary prevention, implantation is recommended after documented VF or haemodynamically significant VT without a transient cause and more than 48 hours after the onset of myocardial infarction; for primary prevention after myocardial infarction, with LVEF of 35% or less and NYHA class II–III heart failure on optimal medical therapy, no earlier than 40 days after the infarction and 90 days after revascularisation. The decision to implant an ICD is made only if life expectancy is more than 1 year. In scar-related VT the target of catheter ablation is the critical isthmus of the re-entry circuit. Ablation is recommended for patients with coronary heart disease and recurrent symptomatic sustained monomorphic VT or ICD shocks despite ongoing antiarrhythmic therapy; for VT from the right ventricular outflow tract it is the first-choice treatment. ## When to call an ambulance Sudden collapse without warning, loss of consciousness and absence of breathing and pulse are signs of cardiac arrest. If someone has lost consciousness, call your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK). The Russian guideline requires immediate cardiopulmonary resuscitation in cardiac arrest, with emergency defibrillation as its key element: with immediate defibrillation the chances of restoring a normal rhythm are much higher than with delayed defibrillation. That is why automated external defibrillators are recommended in places where many people gather, such as schools, airports, railway stations and stadiums. The chances of survival are higher if the arrest is witnessed, if bystanders start resuscitation early and if defibrillation is early. The Russian guideline advises calling an ambulance if an arrhythmia episode comes with dizziness, weakness, feeling faint, loss of consciousness or a fast heartbeat. An ambulance should also be called if an ICD fires (delivers a shock or another treatment). NICE regards as warning signs a blackout during exertion, and a blackout in a person with a family history of sudden cardiac death under the age of 40 or an inherited heart condition: such a person is referred urgently for cardiovascular assessment, and a specialist reviews the referral within 24 hours (the recommendation covers people over 16).