V-TACH VS. V-FIB: DIFFERENCES AND SIMILARITIES

Ventricular tachycardia and ventricular fibrillation are ventricular arrhythmias, which are abnormal heart rhythms originating in the ventricles (the heart's lower chambers that pump blood).

Ventricular tachycardia, called  V-tach, is a potentially dangerous heart arrhythmia. It may cause dizziness or palpitations and even cardiac arrest and death if it lasts more than a few seconds.

Ventricular fibrillation, called V-fib, is the most dangerous arrhythmia. It's characterized by rapid, chaotic electrical activity that causes the ventricles to quiver (fibrillate) instead of beating normally. V-fib causes cardiac arrest within seconds and death within minutes if not treated.

This article will review V-tach and V-fib, including what causes these abnormal heart rhythms, what they look like on an electrocardiogram (ECG), and how they are managed.

Defining Characteristics of V-Tach vs. V-Fib

The heart is a muscular organ with four chambers—two atria (upper chambers) and two ventricles.

Learn More: The Heart: Anatomy, Function, and Conditions

Within the top of the upper right heart chamber is the heart's pacemaker, a group of cells called the sinoatrial node (SA node). These cells create electrical signals that start each heartbeat.

The electrical signals the SA node produces move throughout the heart in a coordinated manner—along a specific route and at particular speeds.

With ventricular arrhythmias, the electrical signals originate within the ventricles. In other words, they do not start in the SA node and move along the usual route of the heart muscle.

Specifically, with V-tach, an area within the left or right ventricle usually takes over as the heart's pacemaker, causing the heartbeat to quicken.

With V-fib, multiple electrical signals within different locations in the ventricles are all created and distributed simultaneously, creating an irregular and erratic heartbeat.

V-Tach

  • A fast, abnormal rhythm starts in the ventricles and may last a few seconds or longer.

  • Ventricles contract rapidly, but usually regularly.

  • V-tach can be life-threatening if it's sustained (lasting more than 30 seconds).

V-Fib

  • A fast, abnormal rhythm starts in the ventricles and prevents blood from being pumped throughout the body.

  • Ventricle walls twitch or quiver uncontrollably and irregularly.

  • V-fib is always life-threatening, causing sudden cardiac arrest.

Related: What Is Non-Sustained Ventricular Tachycardia (NSVT)?

Both V-Tach and V-Fib Are a Medical Emergency

V-tach may cause no symptoms, especially if the episode is brief. Usually, though, a person with V-tach experiences significant palpitations, a sensation that the heart is beating too fast or seemingly skipping beats.

Other possible symptoms of V-tach include:

These symptoms occur because the ventricles cannot adequately fill or pump blood due to the rapid heartbeat and the lack of coordinated contractions (pushing blood out of the chambers).

If the V-tach persists and is not treated promptly, it can progress to V-fib.

With V-fib, the ventricles twitch or quiver instead of pumping blood to the rest of the body as they should. This leads to sudden cardiac arrest within seconds and, in severe cases, death.

Sudden cardiac arrest (SCA) means the heart has suddenly stopped beating because of an electrical problem in the heart. SCA results in sudden cardiac death (SCD) if not treated because blood cannot reach the brain or other vital organs.

Symptoms of sudden cardiac arrest include gasping for air or not breathing, sudden collapse, and loss of consciousness.

What Percentage of Deaths Are From SCD?

An estimated 25% of all worldwide deaths are attributed to sudden cardiac death, with up to 300,000 cases occurring in the United States annually. In the majority of witnessed cases, V-fib is the final arrhythmia seen.

Keep in mind that V-tach can also cause sudden cardiac arrest on its own, thereby skipping V-fib. As such, V-tach that is not stopping or lasts at least 30 seconds (sustained V-tach) is an emergency medical condition.

Related: Difference Between Heart Attack and Cardiac Arrest

How Do V-Tach vs. V-Fib Cause Cardiac Arrest?

V-tach and V-fib usually arise from an underlying structural heart condition, namely coronary heart disease or heart failure.

Coronary Artery Disease

The coronary arteries supply oxygen-rich blood to the heart. When fatty deposits (plaque) narrow or clog the arteries, blood cannot flow properly, causing symptoms like chest pain (angina) and trouble breathing. If blood flow is completely blocked, a heart attack may occur.

The heart muscle weakens after one or more heart attacks, and scar tissue forms. A weak heart and scar tissue leads to abnormal electrical circuits and disruption of the heart's regular electrical activity. These factors can produce dangerous arrhythmias like V-tach and V-fib.

Factors that increase a person's risk for coronary artery disease include:

Heart Failure

Heart failure may result from coronary artery disease or years of uncontrolled high blood pressure, among other reasons. Heart failure triggers electrical remodeling of the ventricles (changes in how the electrical signals travel in the ventricles), especially as the heart failure becomes more advanced and severe, increasing the risk of ventricular arrhythmias.

Other Causes

Other heart conditions that may cause V-tach or V-fib include:

Less commonly, inherited conditions like long QT syndrome or Brugada syndrome may cause V-tach or V-fib, especially in young people.

Causes of V-tach and V-fib unrelated to the heart include:

ECG Results: V-Tach vs. V-Fib

V-tach and V-fib can be diagnosed on an electrocardiogram (ECG), which is a recording of the heart's electrical signaling.

V-tach and V-fib may also be seen on a hospital cardiac telemetry monitor or an automatic external defibrillator (AED).

What Is an AED?

An AED is a portable device that can be used when a person has lost consciousness due to sudden cardiac arrest. It analyzes the heart rhythm and can deliver an electrical shock that helps the heart start and establish a regular rhythm.

V-tach is characterized by wide QRS complexes on the ECG. The QRS complex represents the electrical signal traveling across the ventricles.

With V-fib, there are chaotic waves with no discernible QRS complexes. The pattern of the waves can be categorized in two ways:  

  • Coarse V-fib: When the waves measure 3 millimeters (mm) or greater
  • Fine V-fib: When the waves measure less than 3 mm

Compared to fine V-fib, coarse V-fib tends to occur early after the onset of cardiac arrest and is more likely to be shocked into a normal heart rhythm.

Related: How Cardiac Arrhythmias Are Diagnosed

V-Tach and V-Fib Treatment Approaches

Treatment for V-tach depends on factors like a person's symptoms and the duration of the V-tach episodes.

Non-Sustained V-Tach

No treatment is usually needed if V-tach episodes are brief (non-sustained) and asymptomatic. An exception would be if a person has an underlying heart condition like coronary artery disease or heart failure. In that case, therapy directed toward that condition will be optimized.

If a person's V-tach episodes are non-sustained but symptomatic, medication to control heart rate (e.g., a beta-blocker) may be prescribed. Sometimes, an antiarrhythmic drug like Cordarone or Pacerone (amiodarone) is also added.

Sustained V-Tach

Emergency medical attention is required if a person's V-tach is sustained (lasting more than 30 seconds). Precise treatment steps depend on the person's stability.

If a person is experiencing sustained V-tach and is hemodynamically stable (awake with no symptoms/signs like chest pain or low blood pressure ), intravenous (given through a vein) medication may be urgently administered to slow the heart down and restore the rhythm.

On the other hand, if the person is not hemodynamically stable—perhaps they are experiencing chest pain or having low blood pressure but are still alert and awake—a healthcare provider will likely perform electrical cardioversion. In this procedure, external electric shocks are applied to the heart to correct the rhythm.

Pulseless V-Tach or V-Fib

If V-tach progresses into sudden cardiac arrest (no pulse) or V-fib, the first response is cardiopulmonary resuscitation (CPR) and electrical defibrillation. CPR restores blood flow to vital organs, while defibrillation "shocks" the heart to restore its normal rhythm.

Steps for Sudden Cardiac Arrest Outside of Hospital

If cardiac arrest occurs outside the hospital, call 911, start CPR, and use an automated external defibrillator (AED), if one is available. Pulseless V-tach and ventricular fibrillation are two AED shockable rhythms.

V-Tach vs. V-Fib: After Treatment

Multiple therapies are often involved in helping prevent future episodes of V-tach or V-fib. They include:

  • Medications like a beta-blocker and/or amiodarone
  • Catheter ablation: A procedure that uses radiofrequency energy to destroy the part of the heart tissue that is sending abnormal electrical signals
  • An implantable cardioverter defibrillator (ICD): A small electronic device placed in certain people at high risk of sudden cardiac

Adopting healthy lifestyle habits may help prevent V-tach/V-fib episodes in the first place. These habits include:

  • Eating a low-fat diet
  • Increasing physical activity (under the guidance of a healthcare professional)
  • Avoiding smoking
  • Controlling high blood pressure or cholesterol
  • Managing stress (e.g., mindfulness)

Related: How Smoking Affects Your Heart

Summary

Ventricular tachycardia (V-tach) and ventricular fibrillation (V-fib) are two rapid, dangerous arrhythmias that originate in the ventricles (the lower chambers of the heart).

Ventricular fibrillation is the most deadly arrhythmia. It causes the ventricles to "quiver," preventing blood from being adequately pumped throughout the body, leading to cardiac arrest within seconds.

Ventricular tachycardia becomes a medical emergency when sustained (lasting more than 30 seconds), as it can progress into V-fib and cause sudden cardiac arrest.

Treatment of V-fib and pulseless V-tach requires CPR and electrical defibrillation ("shocking" the heart). Medication to slow the heart rate or restore the heart's normal rhythm may be used in people with non-sustained V-tach who experience symptoms like palpitations or light-headedness.

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