Ventricular tachycardia, commonly called V-tach or VT, is a dangerously fast heart rhythm that originates in the lower chambers of the heart (the ventricles) and drives the heart rate above 100 beats per minute. In many cases the rate climbs well beyond that. Because the ventricles are responsible for pumping blood to the body and lungs, a rhythm this fast doesn’t give them enough time to fill between beats, which can sharply reduce blood flow to the brain, organs, and the heart muscle itself.
How V-Tach Differs From a Normal Fast Heart Rate
A normal heartbeat begins in the upper chambers (atria), travels through an electrical relay station in the middle of the heart, and then activates the ventricles in a coordinated wave. V-tach skips that orderly path. Instead, an abnormal electrical signal fires rapidly from within the ventricle tissue itself, causing the lower chambers to contract too quickly and out of sync with the upper chambers.
The most common trigger for this abnormal signal is a reentry circuit, where electrical impulses loop repeatedly through scar tissue in the heart muscle. Scar from a prior heart attack is the single most common cause of sustained V-tach. Less often, V-tach results from abnormal cells in the ventricles that fire on their own or from electrical “aftershocks” that re-trigger the heart before it has fully recovered from the previous beat.
On an ECG (the standard heart-tracing test), V-tach shows up as a series of wide, abnormal electrical complexes lasting longer than 120 milliseconds each, at a rate above 100 beats per minute. These wide complexes are the hallmark that distinguishes it from fast rhythms originating higher up in the heart.
Sustained vs. Nonsustained V-Tach
The distinction that matters most is how long an episode lasts. Nonsustained V-tach is a burst of three or more rapid ventricular beats that stops on its own within 30 seconds. It can happen without any noticeable symptoms and is sometimes caught incidentally on a heart monitor. Sustained V-tach lasts longer than 30 seconds or causes symptoms severe enough to require immediate treatment before that threshold. Sustained episodes are far more dangerous because the longer the heart races in this pattern, the less blood it pumps and the higher the risk of collapse or progression to an even more lethal rhythm.
What Causes V-Tach
Scarring from a previous heart attack is the leading cause. The scar creates zones where electrical signals slow down and circle back on themselves, forming the reentry loops that sustain the arrhythmia. Other structural heart conditions that can produce V-tach include dilated cardiomyopathy (a weakened, enlarged heart), hypertrophic cardiomyopathy (abnormally thick heart muscle), arrhythmogenic right ventricular cardiomyopathy, and cardiac sarcoidosis.
V-tach can also occur in people with structurally normal hearts. In these cases, the rhythm typically arises from a small focus of abnormal electrical activity rather than scar-related loops. This form, sometimes called idiopathic V-tach, tends to originate near the outflow tracts where blood exits the ventricles and generally carries a better prognosis.
Additional triggers include severe electrolyte imbalances (particularly low potassium or magnesium), certain medications that affect the heart’s electrical timing, inherited conditions that alter the heart’s ion channels (such as long QT syndrome), and acute ischemia, where part of the heart muscle isn’t getting enough blood flow in real time.
Symptoms: Stable vs. Unstable
What you feel during V-tach depends largely on how fast the rate is, how long it continues, and whether your heart has underlying disease. The rapid ventricular rate slashes the amount of blood the heart can push out with each beat. In someone whose heart is already weakened, that drop in output can be catastrophic.
Stable V-tach means the heart is still generating enough blood pressure to keep organs perfused. You might feel a racing or pounding heartbeat, lightheadedness, chest pressure, or shortness of breath, but you remain conscious and alert. Unstable V-tach produces more alarming signs: dangerously low blood pressure, severe dizziness, fainting, altered consciousness, or chest pain. Pulseless V-tach, the most extreme form, means the heart is beating so ineffectively that no pulse can be felt. It is treated identically to cardiac arrest.
Why V-Tach Is a Medical Emergency
The central danger is that V-tach can degenerate into ventricular fibrillation (V-fib), a completely chaotic rhythm where the ventricles quiver instead of pumping. V-fib produces no meaningful blood flow and is fatal within minutes without defibrillation. V-fib is strongly associated with sudden cardiac death, and V-tach often represents the rhythm that precedes it.
Survival rates illustrate the stakes. Only about 10% of people who experience cardiac arrest outside a hospital survive to be discharged. When the arrest is witnessed and the initial rhythm is V-fib or pulseless V-tach, survival improves to roughly 30%. For cardiac arrest that happens inside a hospital, survival to discharge reaches approximately 44%. Every minute without treatment lowers the odds.
How V-Tach Is Treated in an Emergency
Treatment hinges on whether the person has a pulse and whether they’re hemodynamically stable. Pulseless V-tach is treated with immediate CPR and electrical defibrillation, following the same cardiac arrest protocol used for V-fib. If the initial shock doesn’t restore a normal rhythm, medications are given intravenously to help the next shock succeed.
Unstable V-tach with a pulse calls for synchronized cardioversion, a precisely timed electrical shock delivered while the person is sedated. Stable V-tach may be managed initially with intravenous anti-arrhythmic medications, but if the rhythm doesn’t convert or the person’s condition worsens, cardioversion follows.
Long-Term Prevention
After an episode of V-tach, the priority shifts to preventing recurrence and protecting against sudden death. The cornerstone of long-term prevention for many patients is an implantable cardioverter-defibrillator (ICD), a small device placed under the skin that continuously monitors heart rhythm and delivers a shock if it detects a life-threatening arrhythmia.
Current guidelines from the American College of Cardiology give their strongest recommendation for an ICD in patients whose heart pumps 35% or less of the blood in the left ventricle with each beat (normal is roughly 55 to 70%), who have moderate heart failure symptoms despite optimized medications, and whose life expectancy is at least one year. Patients who have had a heart attack and whose pumping function is below 30% also qualify, even without symptoms. An ICD is not recommended for people with severe, end-stage heart failure who are not candidates for advanced therapies or have less than a year to live, because the device is unlikely to improve their overall outcome.
Catheter Ablation
Catheter ablation is a procedure where a thin, flexible wire is threaded through a blood vessel to the heart. The tip of the catheter delivers targeted energy (heat or cold) to destroy the small patches of tissue responsible for generating or sustaining the abnormal rhythm. It’s used when V-tach keeps recurring despite medication, or when frequent ICD shocks are reducing quality of life.
Success rates vary considerably depending on the type of heart disease involved. In patients with scar from a prior heart attack, one major trial found 88% were free of V-tach recurrence at two years after ablation, compared with 67% who received no ablation. Other studies in the same population have reported less optimistic numbers, with recurrence rates of 49 to 56% within one year, reflecting the complexity and variability of scar patterns.
Results are generally less durable in people with non-ischemic cardiomyopathy, where one-year freedom from recurrence hovers around 40%, compared with roughly 57% in those with heart attack-related scarring. Cardiac sarcoidosis poses the greatest challenge, with V-tach recurrence rates as high as 75% within six months of ablation. In contrast, certain inherited conditions like hypertrophic cardiomyopathy show more encouraging outcomes, with about 70% of patients remaining free of V-tach at roughly 20 months. Ablation is rarely a one-and-done solution for complex heart disease, but it can significantly reduce the burden of episodes and ICD shocks, improving day-to-day quality of life even when it doesn’t eliminate V-tach entirely.