Without treatment, some arrhythmias can lead to life threatening complications, such as heart failure, cardiac arrest, or a stroke.

Arrhythmia is the term used to describe an irregular or abnormal heartbeat. A person with an arrhythmia might have a heart that beats too fast, too slowly, or irregularly.

In this article, we discuss the types of arrhythmia that can be life threatening and outline their causes, symptoms, risk factors, and treatment.

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Arrhythmia is a condition that causes the heart to beat abnormally or irregularly. Arrhythmia can cause a person’s heart to beat too fast, too slowly, or with an irregular rhythm.

If people do not receive treatment for arrhythmia, it can lead to life-threatening complications, such as heart failure, stroke, or cardiac arrest. The heart may not be able to pump blood around the body properly, which can damage organs, such as the brain and heart.

Arrhythmias happen when there are changes in heart tissue or in the electrical impulses that control the heartbeat. Multiple factors can cause these changes, such as damage from disease, toxins, stress, injury, or a person’s genetics.

According to the National Heart, Lung, and Blood Institute (NHLBI), a person may not notice any symptoms of arrhythmia. Alternatively, people can notice symptoms occasionally, and these may become more frequent over time.

It is possible for a person to feel an irregular heartbeat. It may feel like their heart has skipped a beat or that it is slow or racing.

More serious symptoms of arrhythmia include:

Some types of arrhythmia can cause a person to have a sudden cardiac arrest (SCA), which can be life threatening. According to the Arrhythmia Alliance, SCA is a condition where the heart suddenly stops working due to a malfunctioning of its electrical system.

A person may show the following signs of having a cardiac arrest:

  • unresponsiveness and not responding to tapping on the shoulders
  • loss of consciousness
  • lack of normal breathing — for example, a person may stop breathing entirely or gasp for breath
  • lack of pulse

Learn more about SCA here.

We outline the types of arrhythmia that can lead to SCA below.

Ventricular fibrillation (V-fib) is the most serious arrhythmia and is a life threatening medical emergency.

Disordered electrical signals in the heart cause the ventricles to quiver instead of pumping normally. This quiver is known as fibrillation.

When the ventricles fibrillate, it can prevent the heart from pumping blood. This can cause the heart to collapse and trigger SCA.

One 2021 article states that nearly 70% of cardiac arrest patients have V-fib.

Causes of V-fib

A number of factors can cause V-fib, including:

  • poor blood flow to the heart muscle
  • damaged heart muscle
  • cardiomyopathy
  • issues with the aorta
  • toxicity from drugs
  • sepsis

Treatment of V-fib

If someone is having a cardiac arrest, a person should respond quickly and follow these steps:

  1. call 911 for emergency medical assistance
  2. give the person CPR
  3. use an automated external defibrillator (AED) if available

Learn more about how to perform CPR here.

Ventricular tachycardia is a condition that affects the lower chambers of the heart (ventricles). It causes a person’s heart rate to reach 100 bpm or higher.

Some people’s hearts may tolerate ventricular tachycardia and not collapse, but for others, it can be life threatening, requiring immediate treatment. This also depends on the extent of the condition and whether the arrhythmia affects other heart structures and functions.

Sometimes, a person with an arrhythmia can feel well, but their heart might pump so fast that it increases pressure in the heart. This can cause fluid to back up in the lungs or the heart muscle to become weak and unstable.

According to the American Heart Association (AHA), ventricular tachycardia happens when electrical impulses in the heart’s lower chambers start firing abnormally. This interferes with signals from the heart’s natural pacemaker, the sinoatrial (SA) node, resulting in a faster heart rate than normal.

Causes of ventricular tachycardia

There are a number of factors that can cause ventricular tachycardia. These include:

  • lack of blood flow to the heart, depriving the heart tissues of oxygen
  • cardiomyopathy that distorts the structure of the heart
  • illicit drug use
  • medication side effects
  • sarcoidosis, which is an inflammatory disease affecting skin or body tissues

Treatment of ventricular tachycardia

According to the AHA, the cause of a person’s ventricular tachycardia will help a medical professional decide on the right treatment.

Common treatments for ventricular tachycardia include medication, surgery, or catheter ablation with radiofrequency ablation.

If a person is in cardiac arrest, they may require immediate electrical defibrillation to restore a normal heartbeat.

High-grade atrioventricular heart block (HAVB) is the most serious type of heart block. A heart block occurs when the electrical signal between the heart’s atria, the upper chambers, and the ventricles is blocked and not conducted through the usual pathway. This can cause the heart to beat slowly or irregularly.

There are two types of HAVB: second degree or type two, and third degree or complete heart block. It happens when there are no electrical signals reaching the ventricles from the atria. HAVB can result in bradycardia, which is a slow heart rate. This in turn leads to fatigue, shortness of breath, or loss of consciousness/fainting.

If a person does not receive immediate treatment, their chances of surviving a complete heart block are very low. Doctors may fit a temporary pacemaker as the first line of treatment, use medications to increase heart rate, or go straight to a permanent pacemaker.

Congenital complete heart block can be discovered at birth or may be due to other conditions. According to the NHLBI, children who have a congenital heart block often have mothers with an autoimmune disease, such as lupus.

Causes of HAVB

HAVB has a number of possible causes, including:

  • congenital heart disease
  • coronary heart disease
  • thickened heart muscle
  • certain medicines
  • heart attack
  • cardiomyopathy
  • some lung conditions
  • infections such as Lyme disease
  • heart procedures such as ablation or surgery
  • electrolyte problems, such as high or low blood levels of calcium, magnesium, and potassium
  • aging of the heart’s electrical pathways

Treatment for HAVB

A person will need to have an EKG in the hospital, which shows the electrical rhythm of the heart and can help doctors diagnose HAVB.

Doctors usually insert a pacemaker for anyone with HAVB that is causing a slow heart rate or other symptoms.

If a person’s HAVB is due to a heart attack, doctors may insert a temporary pacemaker. If the heart rhythm does not return to normal soon after the heart attack, doctors will insert a permanent pacemaker.

If a person has HAVB due to medications or electrolyte imbalances, doctors will give treatments to reverse the medications or correct the imbalances.

Sick sinus syndrome happens when the SA node does not function normally. The SA node, an area of specialized cells in the atria, usually sends electrical signals to the rest of the heart that trigger the cardiac muscle to contract and pump blood. It is the pacemaker of the heart.

In sick sinus syndrome, the SA node malfunctions or something disrupts the electrical impulses. This can make the heart beat too slowly, too fast, or switch between the two, known as tachycardia-bradycardia syndrome.

This condition is most common in older adults, but it can affect people of any age. It can increase the risk of complications such as atrial fibrillation, heart failure, syncope, cardiac arrest, and stroke.

Causes of sick sinus syndrome

The genetic or environmental factors that can cause sick sinus syndrome include:

  • mutations in particular genes, which are usually not inherited
  • muscular dystrophy
  • abnormal inflammation
  • a shortage of oxygen, or hypoxia
  • trauma to the SA node, which can happen during heart surgery
  • medications
  • age-related changes in the heart, such as fibrosis or hardening of the SA node

Treatment for sick sinus syndrome

Doctors usually treat sick sinus syndrome by changing medicines if they could be contributing to the condition or inserting a pacemaker to control a person’s heartbeat.

Can other arrhythmias be dangerous?

There are other arrhythmias that can have dangerous complications. These include:

  • Long QT syndrome (LQTS): This rare disorder causes the heart’s ventricles to take too long to contract and release. This can cause rapid, uncoordinated heartbeats. Long QT syndrome can cause fainting or SCA. According to the NHLBI, for about 1 in 10 people with LQTS, SCA is the first sign of the disorder.
  • Short QT syndrome (SQTS): This extremely rare genetic disorder is when the heart muscle takes less time than usual to contract and release. It can cause life threatening arrhythmias to occur when a person is resting or during exercise, with no apparent trigger.
  • Torsades de pointes: This is a complication of LQTS and happens when the ventricles beat faster than the atria. It can develop into ventricular fibrillation, which is a medical emergency. A person with torsades de pointes will need immediate medical care.

Learn more about heart block here.

There are a number of factors that can increase a person’s risk of developing arrhythmia. They include:

  • Heart disease: Certain types of heart disease, such as from high blood pressure, can increase a person’s chances of developing arrhythmia.
  • Age: A person’s chances of developing arrhythmia increase as they get older.
  • Congenital conditions: If a person is born with a congenital heart defect, it may increase their risk of arrhythmia.
  • Chemical agents: Certain chemical agents can also cause arrhythmias. If a person has exposure to high levels of certain minerals such as potassium, magnesium, and calcium, this may increase their risk of developing arrhythmia. Some cardiac medications can also cause arrhythmia.
  • Smoking: A 2018 review concluded that tobacco use can increase a person’s chances of developing atrial fibrillation.
  • Recreational drug use: Using illicit drugs, such as cocaine and amphetamine, can increase a person’s chance of developing arrhythmia.
  • Cardiomyopathy: A group of conditions in which the walls of the heart chambers become thickened, stiff, or stretched. There are several types of cardiomyopathy, which are mostly inherited and seen in children and young people.

There are a number of steps that a person can take to lower their chances of developing arrhythmia. These include:

If a person is experiencing symptoms of arrhythmia, they should contact a doctor. Some symptoms may require immediate care, while others may have links to underlying conditions that need diagnosis and treatment.

If someone is experiencing chest pain or pressure inside their chest, then they may be having a heart attack. A person should call 911 immediately and carry out CPR.

Arrhythmia is the term for an irregular or abnormal heartbeat. The heart may beat too fast, too slow, or irregularly.

Many types of arrhythmia are not a cause for concern. However, without treatment, some arrhythmias can cause cardiac arrest or lead to other serious complications.

Common symptoms of arrhythmia include feeling faint, dizziness, weakness, fatigue, and a pounding sensation in the chest.

Factors that can increase a person’s chances of having an arrhythmia include a history of heart disease, becoming older, having a congenital heart defect, exposure to some chemical agents, smoking, and recreational drug use.

To lower the chances of developing an arrhythmia, a person can take steps to reduce high blood pressure, lower their cholesterol levels, maintain moderate weight, and eat a heart-healthy, balanced diet. They may also wish to stop or avoid smoking, avoid secondhand smoke, become physically active, and reduce alcohol consumption.