What is heart block?
Electrical signals control the beating of your heart. They tell your heart muscle
when to contract, a process known as conduction. The normal timing of heartbeats is
generated in the upper chamber of the heart (atria) in a structure called the sinus
node. The signal moves from the sinus node to the pumping chambers (ventricles) of
the heart to cause a heartbeat (contraction). When you have heart block, there is
interference with the electrical signals that usually move from the atria to the ventricles.
. This is known as a conduction disorder. If the electrical signals can’t move from
your atria to your ventricles, they can’t tell your ventricles to contract and pump
In most cases of heart block, the signals slow down, but don't completely stop. Heart
block is called first-, second-, or third-degree:
First-degree heart block is the least severe. The electrical signals slow down as they move from your atria
to your ventricles. You may not need any treatment for first-degree heart block.
Second-degree heart block means that the electrical signals between your atria and ventricles can intermittently
fail to conduct. There are 2 types of second-degree heart block
Mobitz type I: The electrical signals get slower and slower between beats. Eventually your heart
drops a beat.
Mobitz type II: The electrical signals sometimes get to the ventricles, and sometimes they don't.
There is no progressive slowing of the electrical signal. This type of heart block
can often progress to third-degree heart block.
Third-degree heart block is the most severe. Electrical signals don't go from your atria to your ventricles
at all with this type. There is a complete failure of electrical conduction. This
can result in no pulse or a very slow pulse if a back up heart rate is present.
What causes heart block?
If you are born with heart block, it's called congenital heart block. It is caused
by a condition your mother had during her pregnancy or heart problems you were born
For most, heart block develops as you get older. It happens as the wires (nerve fibers)
that connect the top and bottom of the heart develop fibrosis and eventually fail.
Sometimes this may happen because of advancing age. Any process that can damage these
heart wires can result in heart block. Coronary artery disease with and without a
heart attack is one of the most common causes of heart block. Diseases that weaken
the heart muscle (cardiomyopathies) can also damage the wire. Heart block can also
be caused by any disease that can affect the heart such as sarcoidosis and certain
cancers, or any disease that results in heart inflammation. This can be an autoimmune
disease or infections. Electrolyte problems such as high potassium levels can also
result in heart block.
Who is at risk for heart block?
. You may be born with heart block (congenital). But many cases of heart block occur
because of some other condition or event. These include:
Heart attack or coronary artery disease
High potassium levels
Certain inherited neuromuscular diseases
Medicines that slow the heart rate
After open heart surgery
What are the symptoms of heart block?
Symptoms depend on the type of heart block you have: First-degree heart block may
have no bothersome symptoms.
Second-degree heart block might cause:
Third-degree heart block can be fatal. It might cause:
How is heart block diagnosed?
To diagnose your condition, your healthcare provider will consider:
Your overall health and health history
Any family history of heart block or heart disease
Medicines you are taking
Lifestyle choices, such as smoking or using illegal drugs
Your description of symptoms
A physical exam
An electrocardiogram (ECG) that records your heart’s electrical impulses
Testing with a Holter or event monitor to track your heart’s rhythm for a period of
time. You might wear a Holter monitor for 24 or 48 hours, or an event monitor for
a month or more. These help capture changes in your heart’s rhythm, even if they don't
occur often or predictably.
Implantable loop recorder. This is a small heart recorder that is placed under the
skin over the heart. It can record up to 3 years.
How is heart block treated?
You treatment depends on the type of heart block you have:
With first-degree heart block, you might not need treatment.
With second-degree heart block, you may need a pacemaker if symptoms are present or
if Mobitz II heart block is seen.
With third-degree heart block, you will most likely need a pacemaker.
Your medical team may also make changes in any medicines you're taking or treat any
related underlying condition.
What are the possible complications of heart block?
Complications of heart block may include fainting with injury, low blood pressure,
damage to other internal organs, and cardiac arrest.
Can heart block be prevented?
Pregnant women who have an autoimmune disease may be able to get certain treatment
to reduce the risk for heart block in their babies.
Prevention of heart block focuses mainly on managing the risk factors. A healthy
lifestyle helps overall good health, including heart health. Exercise, eat a well-balanced
diet, and don’t smoke. Understanding the risks of your medicines and reviewing them
with your healthcare provider can reduce the risk for medicine-induced heart block.
Talk with your healthcare team before taking any herbal supplements or new medicines,
especially if you have risk factors for heart block.
Living with heart block
Follow your healthcare provider’s recommendations for taking medicine and using a
pacemaker, if that applies to you. Also always keep follow-up appointments to make
sure your treatment is on track.
To improve your quality of life with a pacemaker, you may need to:
Stay out of situations in which your pacemaker may be disrupted. This includes being
near an electrical device or devices with strong magnetic fields.
Carry a card that lets people know what kind of pacemaker you have.
Tell all of your healthcare providers that you have a pacemaker.
Get routine pacemaker checks to make sure your device is working well
Stay active, but don't take part in contact sports.
Wear a medical alert bracelet or necklace.
When should I call my healthcare provider?
Seek medical attention right away for these symptoms:
If you have sudden cardiac arrest, you won't be able to seek care for yourself. It
is very important to make sure the people you see on a regular basis know what to
do in an emergency. Calling 911 is the most important first step.
Heart block occurs when the electrical signals from the top chambers of your heart
don’t conduct correctly to the bottom chambers of your heart.
There are 3 types of heart block. First-degree heart block may cause few problems.
Third-degree heart block can be life threatening.
Heart block may cause no symptoms or it may cause dizziness, fainting, the feeling
of skipped or irregular heartbeats, chest pain, trouble breathing, fatigue, or even
Depending on your degree of heart block, you may not need treatment. For some, a
pacemaker is advised.
Tips to help you get the most from a visit to your healthcare provider:
Know the reason for your visit and what you want to happen.
Before your visit, write down questions you want answered.
Bring someone with you to help you ask questions and remember what your provider tells
At the visit, write down the name of a new diagnosis, and any new medicines, treatments,
or tests. Also write down any new instructions your provider gives you.
Know why a new medicine or treatment is prescribed, and how it will help you. Also
know what the side effects are.
Ask if your condition can be treated in other ways.
Know why a test or procedure is recommended and what the results could mean.
Know what to expect if you do not take the medicine or have the test or procedure.
If you have a follow-up appointment, write down the date, time, and purpose for that
Know how you can contact your provider if you have questions.