What Are the Types of Bradycardia?

Medically Reviewed by James Beckerman, MD, FACC on August 17, 2022
3 min read

If your doctor says you or a loved one has bradycardia, a resting heart beat that's less than 60 beats per minute, it's only part of the diagnosis.

Your doctor will also want to figure out which type it is. They may talk to you about these kinds: sinus bradycardia, sick sinus syndrome, and heart block.

What kind of treatment you get, if any, will depend on how mild or serious your case is, along with which kind you have.

The term “sinus” may make you think of your nasal passages. But when it comes to the heart, it refers to what’s called the sinus node.

That’s a group of cells that sends out electrical signals that tell you when to pump out more blood. It’s sometimes called “the heart’s natural pacemaker.” It should start the signal about 60 to 100 times a minute.

If that node sends out those signals too slowly or fails to fire off a pulse at all, you might have sinus bradycardia.

It is somewhat common in children, athletes, and older adults. It may be mild enough that you never notice any symptoms.

With a more serious case, you might have dizziness, breathing problems, and chest pains, among other problems. You should see a doctor if you have any of these.

Any number of other conditions can scar or injure your sinus node. Some of them are:

  • Heart attack
  • Pericarditis, or inflammation of the thin tissues around the outside of the heart
  • A defect at birth
  • Sleep apnea, or when you briefly stop breathing while you sleep
  • A problem with your thyroid, the gland in your neck that helps control many of your body’s functions
  • Certain medications, including a class of medicines called beta blockers. You may take them to lower blood pressure or for other heart conditions.

This type of bradycardia causes an abnormal heart rhythm. You may have irregular heartbeats or ones that flip between slow and fast.

This syndrome is not as common.

It can be caused by some of the same conditions you see with sinus bradycardia.

It is often the result of heart disease. If you’ve had a heart attack or surgery, the sinus node may be scarred or damaged.

Sometimes the normal wear and tear on your heart as you age is the cause.

Your heart has four chambers. The upper two are called the atria, the lower two are the   ventricles. They pump and squeeze in a rhythm so your body has a steady supply of oxygen-rich blood. They get their “orders” from those electrical signals the nodes send.

But with heart block, that doesn’t happen. The flow of electrical signals from the sinus node down to another collection of cells, called the AV node, is cut off. You might hear your doctor call this “atrioventricular (AV) block.”

It can come in several types. First degree is the mildest and may not even cause symptoms. Third degree is the most serious and is sometimes called “complete heart block.” You may need emergency care for this kind.

Heart block can be what’s called a congenital defect, meaning you were born with it. But most of the time, it comes from something you got later in life.

The main cause is a heart attack. Other conditions can also damage the steady electrical flow between the sinus and AV nodes. They include:

  • Heart failure, because the heart is not pumping enough blood for your body
  • Myocarditis, or inflammation of the heart muscle
  • Coronary artery disease, or narrowing of the arteries in the heart
  • Rheumatic fever, which is most common in children who didn’t get treated well for strep throat or scarlet fever

You may not need any treatment if you have a mild case. Your doctor will just want to keep a watchful eye. If you have a more serious situation, they have a range of options to make you better depending on the type and what may be causing it.

Your doctor may need to change your medications or lower the dose if that’s causing your heart to slow down.

You may need a pacemaker. That’s a small, battery-powered device a surgeon puts in your chest, just under your collarbone, to help you keep a steady heart rate.

Sometimes, you need to treat what’s called an “underlying condition.” For instance, managing thyroid disease or sleep apnea may clear up the slow or erratic heartbeat.