Arrhythmias
Sinus bradycardia
What is sinus bradycardia?
“Bradycardia” is the medical term for a heart that is beating too slowly – less than 60 beats per minute – and sinus bradycardia is the most common type of bradycardia.
Sinus bradycardia is caused by a disruption of normal sinoatrial node (SA node) function. The SA node is a small patch of electrical tissue that sits at the top of the right atrium and sends out the signals that initiate and control our heartbeats. If it is firing slowly – and there can be many reasons for this – sinus bradycardia will be the result.
Heart contractions: Sinus bradycardia vs normal heart
Sinus bradycardia isn’t always a sign that something is wrong. A slow heartbeat can have many causes, some problematic and some not.
And unlike the other arrhythmias we discuss in this section, sinus bradycardia isn’t necessarily always a disorder itself; it can be a symptom of another underlying disorder. It can also be a side-effect of treatment for some other cardiovascular problem.
It’s normal for our hearts to beat slowly sometimes. Many athletes and physically active adults have resting heart rates below 60 beats per minute, and our pulse always slows when we are asleep or relaxing.
However, if your heart rate is persistently too slow, or if you’re experiencing symptoms like general weakness, dizziness, or shortness of breath, your bradycardia may be a sign of underlying disease and then it needs to be checked out by a physician.
If you want learn more about a normal heartbeat take a look at Your heart: The basics.
What causes sinus bradycardia?
An abnormally slow heart rate can be caused by a wide range of different conditions, some quite serious and some not. And, as we said in the above section, many very athletic people have a slow resting heartrate that is normal for them and isn’t a sign of anything wrong.
Electrical signals: Sinus Bradycardia vs normal heart
Paradoxically, regular users of stimulant drugs like cocaine and methamphetamine often have resting bradycardia. This happens because their hearts become acclimated to over-stimulation and they compensate by dialing the rate down so it’s normal when over-stimulated and artificially slow when not.
If you are diagnosed with bradycardia, your doctor may want to run some tests in order to understand more about any underlying causes.
Common causes of sinus bradycardia include:
- Sleep apnea
- Hypothyroidism (underactive thyroid)
- Medications, especially those used to treat other heart conditions, such as beta blockers
- Diseases such as Lyme disease
- Heart surgery complications
- Heart attack
- Sick sinus syndrome: Your SA node, which is your heart’s pacemaker, isn’t triggering reliably
If you want learn more about how your heart works, take a look at Your heart’s electrical system.
What are the symptoms of sinus bradycardia?
Many people with sinus bradycardia experience no symptoms and don’t even know that they have an abnormally slow heartbeat.
However, a very slow heart rate can lead to problems. You may suffer from insufficient blood flow to the brain and other organs, and this can cause a wide range of symptoms.
Here’s a list of some common symptoms of sinus bradycardia:
- Tiredness or weakness
- Dizziness or fainting
- Shortness of breath
How is sinus bradycardia treated?
If your symptoms are severe, your doctor will recommend treatment. Of course, if your sinus bradycardia is the result of an underlying disease, treating that disease will be the first priority.
Treatments for sinus bradycardia include:
- Treatment of any underlying cause or disorder
- Surgical insertion of a pacemaker
- Changes to your medications and/or lifestyle changes
- Avoidance of any medications or drugs that might further slow down your heart rate
What are the aims of treatment?
The aims of treatment for people with sinus bradycardia are to increase and strengthen the heart rate and lessen the severity of symptoms that can make daily living a struggle.
Increasing blood flow to the brain will reduce the risk of fainting attacks and dizziness, and a stronger, faster heart rate will improve energy levels and sleep health.