All About Monomorphic Ventricular Tachycardia

Monomorphic ventricular tachycardia is an irregular heartbeat where the bottom chambers of your heart beat quicker than usual. It can cause symptoms such as shortness of breath, dizziness, or fatigue.

Tachycardia is the medical term for an abnormally fast heartbeat. Ventricular tachycardia is when the bottom chambers of your heart (ventricles) beat too fast.

Short-lasting ventricular tachycardia may not cause any noticeable symptoms. More severe cases may lead to dizziness or shortness of breath. Extreme cases can lead to life threatening cardiac arrest.

What is monomorphic ventricular tachycardia?

Ventricular tachycardia falls into a group of conditions called arrhythmias characterized by abnormal heartbeats that are either:

• too fast
• too slow
• in an unusual rhythm

Ventricular tachycardia is a type of arrhythmia in which the bottom chambers of your heart beat too quickly. This means more than 100 beats per minute for at least three consecutive heartbeats .

Ventricular tachycardia is classified as monomorphic or polymorphic depending on how the electrical activity of your heart appears on an electrocardiogram (ECG) . “Monomorphic” refers to a single repeated abnormality in your heart’s electrical activity that occurs during each heartbeat.

Monomorphic ventricular tachycardia can be divided into two subtypes:

• Sustained: It occurs for more than 30 seconds or causes changes to blood flow within 30 seconds that require treatment.
• Nonsustained: It lasts for less than 30 seconds or doesn’t lead to significant changes in blood flow.

Monomorphic ventricular tachycardia can turn into a serious condition called ventricular fibrillation , in which the bottom chambers of your heart beat irregularly. Ventricular fibrillation is a medical emergency that can lead to cardiac arrest, which is when your heart stops beating suddenly.

Causes of monomorphic ventricular tachycardia

Ventricular tachycardia is associated with conditions or events that cause disruption to the electrical activity of your heart. These may include:

• coronary artery disease
• cardiomyopathy , damage to your heart’s muscle tissue
• sarcoidosis , an inflammatory disease
• structural heart disease, often from a previous heart attack
• congenital heart disease, such as long QT syndrome
• electrolyte imbalances
• medication side effects
• use of stimulants like cocaine or methamphetamines

Monomorphic ventricular tachycardia may be a sign of scarring in your heart’s muscle tissue.

Read more about risk factors for heart arrhythmia .

Symptoms of monomorphic ventricular tachycardia

Minor cases of ventricular tachycardia may only last a few seconds and have no noticeable symptoms. Severe cases may be a life threatening emergency.

When symptoms appear with monomorphic ventricular tachycardia, they may include:

• dizziness
• fainting
• fatigue
• chest pain
• heart palpitations , fluttering or pounding heartbeat
• shortness of breath
• neck tightness

If an episode lasts for more than 30 seconds , it has the potential to lead to cardiac arrest.

People who experience cardiac arrest may:

• collapse suddenly
• stop breathing
• lose consciousness
• not have a pulse

Cardiac arrest often occurs without warning, but some people may experience:

• heart palpitations
• shortness of breath
• weakness
• chest pain

These symptoms combined are always a medical emergency.

Read more about when to worry about heart palpitations .

How is monomorphic ventricular tachycardia diagnosed and treated?

The main diagnostic test for monomorphic ventricular tachycardia is an ECG. During this test, you’ll have adhesive electrodes attached to your chest. These electrodes measure the electrical activity of your heart and provide the doctor with a printout.

The printout includes a line that moves up and down with each heartbeat. People with monomorphic ventricular tachycardia have a single, stable change in their expected heartbeat with no beat-to-beat variation. In other words, the abnormal or unusual electrical pattern is the same in each heartbeat.

Read more about arrhythmia diagnosis tests and doctors .

You likely won’t need treatment if you don’t have symptoms and the doctor doesn’t feel you’re at risk of developing complications of ventricular tachycardia.

People experiencing symptoms or who are at risk of developing cardiac arrest may be treated with:

• antiarrhythmic medications
• beta-blockers
• implantable cardioverter-defibrillators to protect against cardiac arrest
• defibrillation to shock your heart back to its usual rhythm
• a type of surgery called ablation to change electric activity in your heart
• emergency treatments like:
  • oxygen
  • chest compressions
  • breathing tube
  • ventilation

Read more about medications for arrhythmia .

Monomorphic vs. polymorphic ventricular tachycardia

Monomorphic ventricular tachycardia is characterized by a single irregularity in your ECG reading that’s the same for each heartbeat. Polymorphic ventricular tachycardia is characterized by more than one abnormality during each heartbeat.

Acute coronary syndrome is commonly linked to polymorphic ventricular tachycardia.

Outlook

The outlook for people with ventricular tachycardia depends on the underlying cause. People without other heart difficulties often have a positive outlook .

People with ischemic cardiomyopathy, on the other hand, may have a more conservative outlook, with a lower survival rate, especially if left untreated. Ischemic cardiomyopathy is damage to heart muscle from lack of blood flow, often due to a previous heart attack .

Ventricular tachycardia may lead to cardiac arrest, which requires immediate medical treatment with an automated external defibrillator (AED) . People who are treated promptly with an AED have the highest chance of survival.

Monomorphic ventricular arrhythmias aren’t uncommon among athletes. They often don’t cause difficulties but may raise concerns in some cases. Some countries, such as Italy, screen competitive athletes for ventricular arrhythmias that may increase the risk of sudden cardiac death.

Read about the potential complications of heart arrhythmia .

Takeaway

Monomorphic ventricular tachycardia is an abnormal heart rhythm that occurs when the bottom chambers of your heart beat too frequently. Serious cases can cause symptoms such as shortness of breath or fainting. In extreme cases, it can lead to cardiac arrest and sudden death.

A doctor can diagnose monomorphic ventricular tachycardia with an ECG test. The test can also help the doctor rule out other abnormal heart rhythms and determine whether your condition needs treatment.