Sinus Bradycardia

What is sinus bradycardia?

Sinus bradycardia is a type of slow heartbeat. A special group of cells begin the signal to start your heartbeat. These cells are in the sinoatrial (SA) node. Normally, the SA node fires the signal at about 60 to 100 times per minute at rest. In sinus bradycardia, the node fires less than 60 times per minute. Bradycardia means a slow heartbeat. In sinus bradycardia, the heartbeat is starting in the normal part of the electrical system, the SA node.

Many adults and children have normal sinus bradycardia that does not cause symptoms. In these cases, the bradycardia does not mean there is a heart problem. This is very common in young people, in athletes, and in some elderly people, especially during sleep. This is sometimes called physiologic sinus bradycardia. Many people with sinus bradycardia don’t know that they have it. In some cases, sinus bradycardia is a sign of a problem with the heart or another medical condition.

Sometimes, sinus bradycardia happens off and on in response to specific situations. In other cases, it can be permanent. It is more likely to happen during deep sleep. Sinus bradycardia can happen without any other heart rhythm problems. Other times, the heart may skip or drop beats. Sinus bradycardia might slow or block the heart’s signal along its path. In some people, sinus bradycardia alternates with a heartbeat that is too fast. This is called tachycardia. This is referred to as tachycardia-bradycardia syndrome.

What causes sinus bradycardia?

A number of conditions can cause sinus bradycardia. In some cases, the cause is not known.

Causes of pathophysiologic sinus bradycardia include:

  • Advanced age
  • Problems with the SA node (sick sinus syndrome)
  • Inflammatory heart conditions, like pericarditis or myocarditis
  • Heart conditions that exist at birth (congenital)
  • Increased pressure inside the head (for example, in an injury to the brain)
  • Heart attack (myocardial infarction)
  • Obstructive sleep apnea
  • Drugs that affect the SA node and heart rate, like beta-blockers
  • Hypothyroidism
  • Certain rare genetic conditions, like myotonic dystrophy

Causes of physiologic sinus bradycardia include:

  • High-endurance athletic training
  • Pressure on the carotid sinus (for example, from a very tight collar)
  • Vomiting or coughing
  • Bearing down when having a bowel movement
  • Sudden contact with cold water
  • Hypothermia

What are the risks for sinus bradycardia?

Certain factors may increase the risk of bradycardia, such as:

  • Coronary artery disease
  • Diabetes
  • High blood pressure
  • Heart valve disease
  • Cardiomyopathy

What are the symptoms of sinus bradycardia?

Sinus bradycardia often causes no symptoms at all. When it does, they may include:

  • Lightheadedness or dizziness
  • Fainting
  • Fatigue
  • Dizziness
  • Shortness of breath
  • Reduced exercise tolerance
  • Worsened chest pain (if already present)
  • Worsened heart failure (if already present)

In very rare cases, sinus bradycardia can lead to cardiac arrest.

How is sinus bradycardia diagnosed?

Your healthcare provider will take a medical history and give you a physical exam. You will need a test called an electrocardiogram (ECG). This gives a snapshot of your heart rhythm. This test alone is often enough to make the diagnosis. Continuous electrocardiogram, such as Holter or event monitoring, may be used to check the heart for a longer period.

Other tests to diagnose the condition may include:

  • Blood tests to rule out hypothyroidism or other abnormalities
  • Tests to diagnose sleep apnea
  • Exercise stress testing, to check the heart rate’s response to exercise
  • Electrophysiological testing, to check the heart rhythm in more detail
  • Tests to study the autonomic nervous system

How is sinus bradycardia treated?

If you don’t have symptoms, you likely won’t need any treatment. People with symptoms will need treatment. This may include treating a cause such as an underactive thyroid. You may need to reduce or stop medicines that cause the slow heart rate. These can include beta-blockers and calcium channel blockers. Some people may need a temporary or permanent pacemaker. This uses a small electrical current to take over for the heart’s electrical system.

How to manage sinus bradycardia

Lifestyle changes to help manage sinus bradycardia include:

  • Eating a low-salt, heart healthy diet
  • Getting enough exercise
  • Taking medicines to lower cholesterol or treat diabetes

When should I call my healthcare provider?

Call the healthcare provider right away if you have severe symptoms, such as dizziness or fainting. If you notice your symptoms getting worse, plan to see your healthcare provider soon.

Key points about sinus bradycardia

Sinus bradycardia is a kind of slow heartbeat. It happens when the sinoatrial node fires less than 60 times per minute. In some cases, sinus bradycardia is normal, but other times it can mean an underlying problem.

  • Sinus bradycardia can be caused by some health conditions. But in some people, it’s normal.
  • Most people with sinus bradycardia don’t have any symptoms. It is common in athletes and in the elderly.
  • If you do have symptoms, your healthcare provider may remove or reduce any medicines that might be triggering it. Some people need a pacemaker.
  • Follow all of your healthcare provider’s instructions carefully.
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