Bradycardia is known as a slow heart rate, where the heart usually beats fewer than 60 times a minute as opposed to a normal heart, beating between 60 and 100 times a minute in an adult at rest. Bradycardia can be a serious issue to individuals whose hearts don’t pump enough oxygen-rich blood to the body. For some people, however bradycardia doesn't cause symptoms or complications.


Individuals who have bradycardia do not get enough supply of oxygen to the brain and other organs. As a result, they may experience these symptoms:

  • Lightheadedness
  • Tiredness
  • Weakness
  • Faint
  • Shortness of breath
  • Chest pains
  • Bewilderment


Bradycardia is caused when something disrupts the normal electrical impulses controlling an individual’s rate of heart pumping action. Many issues can be the cause for a malfunction of the heart’s electrical system, including:

  • Damage to heart tissues due to heart disease or cardiac attack
  • Damage to heart tissues due to aging
  • High blood pressure (Hypertension)
  • Heart disorder at birth (Congenital heart defect)
  • Heart surgery complication
  • Inflammatory disease such as rheumatic fever or lupus
  • Too much potassium in the blood (Electrolyte imbalance)
  • Infection of heart tissue (Myocarditis)         
  • Increase of iron in organs (Hemochromatosis)
  • Slow electrical impulses of the heart (Hypothyroidism)
  • Disruption of breathing during sleep (Obstructivesleep apnea)
  • Medications

The Heart’s Electrical System

In general, two types of problems result in bradycardias:

  • Disorders of the sinoatrial node (SA node)
  • Disorders of the atrioventricular node (AV node)

The sinoatrial node (SA node) is located in the right atrium and controls the rhythm of the heart. The atrioventricular node (AV node) helps transmit a signal to a specialized collection of cells called the bundle of His, where these cells then transmit the signal down to the left branch serving the left ventricle and right branch serving the right ventricle. This in turn informs the ventricles to contract and pump blood, where the right ventricle sends oxygen-poor blood to the lungs and the left ventricle sends oxygen-rich blood to the body. Bradycardia is what occurs when these electrical signals slow down or are blocked.

Sinus node problems

Bradycardia often starts in the sinus node. A slow heart rate may occur due to:

  • Discharging of electrical impulses at a slower rate
  • Pausing or failing to discharge at a regular rate
  • Discharging an electrical impulse that's blocked before causing the atria to contract

Heart block (atrioventricular block)

Bradycardia may also occur because electrical signals transmitted through the atria aren't transmitted to the ventricles, in turn causing heart block. These heart blocks are classified based on the degree to which signals from the atria reach the heart's main pumping chambers (ventricles).

  • First-degree heart block.: All electrical signals from the atria reach the ventricles, but the signal is slowed down slightly. First-degree heart block is a mild form and usually does not require treatment.
  • Second-degree heart block: Not all electrical signals reach the ventricles. Some beats are dropped, resulting in a slower and sometimes irregular rhythm.
  • Third-degree (complete) heart block: None of the electrical impulses from the atria reaches the ventricles. In this case, the bundles of His or other tissues of the ventricles start to function as a substitute pacemaker for the ventricles. This results in a slow and sometimes unreliable electrical impulse in the heart’s pumping chambers.
  • Bundle branch block: When electrical signals are blocked near the end of the pathway for electrical impulses. The severity of a bundle branch block depends on where both the left and right branches are affected and the presence of other types of heart block, as well as the degree of damage to the heart tissue.


Complications of untreated bradycardia vary depending on how slow the heart rate is and what kind of damage it may present to the heart tissue. Possible complications of a slow heart rate may include:

  • Frequent fainting spells
  • Inability of the heart to pump enough blood (heart failure)
  • Sudden cardiac arrest or sudden death

Risk Factors

There are many risk factors related to individuals facing heart conditions. Some of these risk factors are:

  • Age: bradycardia is most common in older adults with heart problems
  • High blood pressure
  • Smoking
  • Alcohol abuse
  • Use of recreational drugs
  • Psychological behavior


There are many effective ways to prevent bradycardia and reduce the risk of developing heart disease. Some of the following steps can taken to treat of eliminate risk factors:

  • Exercising regularly
  • Eating a healthy diet, rich in fruits, vegetables and whole grains
  • Maintaining a healthy weight
  • Keeping blood pressure and cholesterol under control
  • Eliminating smoking
  • Drinking alcohol in moderation
  • Ending recreational drug use
  • Controlling stress and learning coping techniques
  • Making appointments for physical exams and reporting any signs of symptoms to a doctor