Tachycardia and bradycardia are two types of irregular heart rates. Tachycardia is when the heart beats faster than 100 beats per minute. Bradycardia is when the heart beats slower than 60 beats per minute.

Tachycardia and bradycardia are not always a cause for concern. For example, tachycardia occurs when a person is exercising. Bradycardia can occur when a person is sleeping. It is also common in athletes.

People can also experience abnormal bouts of tachycardia and bradycardia. Medical professionals refer to this as tachy-brady syndrome (TBS).

This article defines tachycardia and bradycardia, along with their associated symptoms, causes, diagnoses, treatments, and outlooks.

It also provides an overview of TBS and answers some frequently asked questions. Finally, it offers advice on when to contact a doctor.

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The American Heart Association (AHA) defines tachycardia in adults as a heart rate faster than 100 beats per minute (bpm).

Healthcare professionals classify tachycardia according to where it originates. Three examples of tachycardia include:

  • Atrial fibrillation (AFib): This is a type of irregular tachycardia originating from the heart’s upper chambers, called the atria.
  • Supraventricular tachycardia (SVT): This is a group of tachycardias involving rhythms above the heart’s lower chambers, called the ventricles. Examples include AV reentrant tachycardia, AV nodal reentrant tachycardia, and atrial tachycardia.
  • Sinus tachycardia (ST): This is a faster-than-normal heart rate that occurs when the heart’s natural pacemaker, called the sinus node, sends out electrical signals faster than usual. This is normal and necessary when a person performs physical activity, like moderate to vigorous exercise.
  • Ventricular tachycardia (VT): This is a rapid heart rate that starts in the ventricles.

The AHA defines bradycardia as a heart rate slower than 60 bpm.

Bradycardia is not always a cause for concern, such as when a person is sleeping. Bradycardia is also common in athletes.

A person cannot have both tachycardia and bradycardia at the same time.

However, a person may develop tachy-brady syndrome (TBS). This is a condition in which the heart’s rate alternates between fast and slow.

A person may experience tachycardia due to AFib alongside sinus node dysfunction, which causes the bradycardia portion of TBS.

The following list outlines some shared symptoms of tachycardia and bradycardia:

Bradycardia more commonly causes:

  • fatigue
  • lightheadedness
  • dizziness
  • fainting

Tachycardia more frequently causes palpitations alongside the faster heart rate.

Tachycardia and bradycardia have different causes. These are outlined below.

Tachycardia causes

The causes of tachycardia include:

Sinus tachycardia has some unique causes, including:

  • exercise
  • anxiety or fright
  • severe emotional distress
  • fever
  • pain

Bradycardia causes

Some potential causes of bradycardia include:

  • problems with the heart’s sinus node
  • problems with the pathways that conduct electrical impulses from the atria to the ventricles
  • heart damage from aging, heart disease, or heart attack
  • congenital heart defects
  • certain heart medications
  • complications from heart surgery
  • an infection of the heart tissue, such as with myocarditis and Lyme disease
  • an imbalance of calcium or potassium in the blood
  • metabolic problems, such as hypothyroidism
  • inflammatory diseases, such as rheumatic fever or lupus
  • obstructive sleep apnea

Many endurance athletes have a heart rate lower than 60 bpm at rest. In these individuals, bradycardia is a sign that the heart is strong and able to effectively pump blood around the body without increasing its pumping rate.

Tachycardia and bradycardia are types of irregular heart rates. Arrhythmias, which are an abnormal heart rhythm, can cause irregular heart rates.

According to the U.K. National Health Service (NHS), the most effective way to diagnose a heart arrhythmia is with an electrocardiogram (EKG). This device records the heart’s electrical activity, rate, and rhythm.

Doctors may advise some people to wear a portable EKG monitor called a Holter monitor for anywhere from 24 hours to 14 days. Others may need to wear an EKG monitor while exercising if physical activity appears to trigger their symptoms.

Other tests doctors may use to diagnose heart arrhythmias and their underlying causes include:

  • Cardiac event recorder: This device records abnormal rhythms whenever they occur.
  • Electrophysiological (EP) study: This test locates the source of electrical signals in the heart. It involves passing soft wires through a vein in the leg and into the heart while a person is under sedation.
  • Other lab tests: A doctor may perform an echocardiogram to look at the structure of the heart. This test uses sound waves to create an image of the heart.

Some possible treatment options for tachycardia and bradycardia are outlined below.

Tachycardia treatments

The treatment for tachycardia depends on the type. Three common types and their associated treatment options are outlined below.

Supraventricular tachycardia (SVT) treatments

People with occasional symptoms due to SVT may not require treatment.

The AHA lists the following techniques that may help stop an episode of SVT. The organization states these are most effective immediately after SVT begins:

  • Carotid sinus massage: This involves applying gentle pressure on the neck, where the carotid artery splits into two branches. Only a trained healthcare professional should perform this technique.
  • Valsalva maneuver: This involves holding the nostrils and mouth closed while exhaling air.
  • Dive reflex: This involves plunging the face into cold water to elicit a decreased heart rate and other physiological changes.

People should discuss whether these techniques are appropriate for them with a healthcare professional.

Prolonged episodes of SVT may require emergency treatments, such as medications that aim to control the heart rate or restore a normal heart rhythm, or cardioversion.

Cardioversion is a procedure that involves delivering a shock through the heart to restore a normal heart rhythm.

People who experience frequent episodes of SVT may require one or more of the following treatments:

  • Catheter ablation: This procedure involves a healthcare professional threading catheters through blood vessels to the heart and using heat, extreme cold, or radio frequency energy to scar a small area of heart tissue. This blocks the conductive pathway responsible for the arrhythmia.
  • Daily medications: These drugs aim to prevent episodes of SVT.
  • Pacemaker: An implanted electrical device, a pacemaker helps override a fast heart rate.
  • Surgery: Surgery aims to correct the electrical signals causing the abnormal heart rhythm.

Sinus tachycardia (ST) treatment

The treatment for ST involves diagnosing and treating the cause of the condition. According to the AHA, simply slowing the heart rate can be harmful if the ST is a symptom of a more serious underlying condition.

Ventricular tachycardia (VT) treatment

The treatment for VT depends partly on the cause. Some potential treatment options include:

  • medications to help prevent arrhythmias
  • radiofrequency ablation, which is a procedure that destroys the cells causing VT
  • implanted cardioverter defibrillator (ICD) surgery, which involves implanting an ICD device that delivers an electrical pulse to the heart to reset an extremely irregular heart rate
  • electrical defibrillation, but only in the event of a life threatening arrhythmia


A doctor may prescribe medications to help control the heart rate. These include:

  • beta-blockers
  • calcium channel blockers
  • antiarrhythmic medications
  • anticoagulants to prevent stroke

Cardioversion, pacemakers, and surgery can also treat AFib.

Bradycardia treatments

People who experience occasional bradycardia may not require treatment.

Treatments for severe or prolonged bradycardia may include adjusting or stopping medications that cause bradycardia as a side effect, or inserting a pacemaker to help regulate the heart’s rhythm.

A person should never make changes to their medication unless their doctor advises them to do so.

The outlook for people with tachycardia depends on the type. Both SVT and VT may cause cardiac arrest in extreme cases. A person should talk with a doctor about the type of tachycardia they have and their individual outlook.

The outlook for people with bradycardia depends on the underlying cause. People with borderline or occasional bradycardia may not require any treatment.

Below are answers to frequently asked questions about tachycardia, bradycardia, and TBS.

How do doctors treat tachycardia-bradycardia syndrome?

TBS falls under the umbrella of sick sinus syndrome, or sinus node dysfunction.

The initial treatment for TBS and other types of sinus node dysfunction involves identifying any factors causing or contributing to the condition and correcting these, where possible. Some people with TBS may require a permanent pacemaker to help regulate their heart rhythm.

Is tachycardia-bradycardia syndrome serious?

TBS and other forms of sinus node dysfunction are generally benign and present a low risk of sudden cardiac death. However, some forms of sinus node dysfunction have associations with heart disease. Additionally, AFib, which is often present with TBS, increases the risk of stroke.

These conditions are treatable. A person can discuss their specific situation with a healthcare professional.

What is the difference between tachycardia, bradycardia, and heart arrhythmias?

Tachycardia and bradycardia are two types of irregular heart rates. Tachycardia is when the heart rate is more than 100 bpm, whereas bradycardia is when the heart rate is slower than 60 bpm.

Arrhythmia is an abnormal heart rhythm. Many arrhythmias can cause a faster or slower heart rate.

A person should contact a doctor if they experience any signs or symptoms of heart arrhythmia, such as chest pain or dizziness, or if they have a personal or family history of heart problems.

Tachycardia and bradycardia are two types of irregular heart rates. Tachycardia is when the heart beats faster than 100 bpm. Bradycardia is when the heart beats slower than 60 bpm.

An electrocardiogram (EKG) is usually the first step in diagnosing an irregular heart rate. Doctors may request additional tests, such as an echocardiogram or a cardiac event recorder.

Some general treatment options for tachycardia and bradycardia include medications, ablation, or a pacemaker. However, some people do not require any treatment.

Some people may experience TBS, in which they have alternating episodes of tachycardia and bradycardia.