Overview 

Bradycardia is when the heart rate is fewer than 60 beats per minute. 

It can be normal. Athletes, in particular, will often have a resting heart rate under 60. A slow heart rate in young, otherwise healthy individuals is also common during sleep. 

However, diseases affecting the normal electrical activity of the heart can cause interruption or block of signals, resulting in slower heart rates. 

Symptoms 

Often a slow heart rate has no symptoms and can be picked up incidentally.

However, it can be associated with: 

  • light-headedness 
  • transient loss of consciousness (syncope) 
  • breathlessness 
  • Fatigue 

Causes 

Bradycardia can be caused by: 

  • age related heart tissue damage 
  • a heart attack
  • something you are born with (congenital) 
  • inflammation of heart muscle (myocarditis) 
  • complication of heart surgery
  • underactive thyroid gland (hypothyroidism) 
  • inflammatory diseases (e.g. lupus) 
  • medications 

The heart is essentially two pumps working in parallel. Each pump consists of two chambers (atria and ventricles).  

The heart has a natural pacemaker (called the SA node) in the right atrium which initiates each heartbeat. The electrical signal spreads from the SA node through the atria before crossing to the ventricles via the AV node.  

Block in any part of this system can cause bradycardia. 

Diagnosis 

Problems with the conduction system of the heart can often be identified on a standard 12-lead ECG. If the issue is intermittent, then continuous ECG monitoring may be required. 

For less frequent issues, you may need to have an implantable loop recorder inserted. 

Treatment 

Bradycardia does not always need treatment, especially if it is not associated with symptoms. 

However, if you have symptoms and we cannot identify a cause which we can reverse, you may need a permanent pacemaker. 

Occasionally, if there is evidence of significant conduction disease, a pacemaker may be recommended even in the absence of symptoms.