Second (Mobitz Type II) and Third Degree Heart Block
Sinus Rhythm: The heart works like an
electrical pump. The sinoatrial (SA) or
sinus node is the heart’s natural
pacemaker. It controls the heart rate. The
sinus node sends an electrical signal to
the top chambers of the heart called the
atria. This causes them to contract. The
atrioventricular (AV) node is like an
electrical conduction cable. It sends the
signal to the lower chambers of the heart
called the ventricles. This causes them
Second-Degree Heart Block
Second-degree AV Block, also called
Mobitz type II, causes some electrical
signals from the atria not to reach the
ventricles. Some atrial signals reach the
ventricles while others are blocked. Your
cardiology provider will decide if your
child needs more evaluation and follow-
Third-Degree Heart Block
Third degree heart block, also called
complete AV block, happens when none
of the electrical signals from the atria
reach the ventricles. When complete
heart block happens, the heart rate is
slower. This is because back-up
pacemaker cells in the AV node or
ventricle control the heart rate. It is rare
(1 in 10,000 newborns).
What are the Signs and Symptoms?
ξ decreased ability to exercise
ξ problems breathing, also called
shortness of breath
Signs and symptoms depend on the type
of heart block and the heart rate. Some
infants and children may not have any
symptoms. In complete heart block,
your child may have bradycardia which
means the heart rate is slower than
If your child has these symptoms call
your cardiology provider. If your child
faints, call 911.
What Causes Heart Block?
ξ Mother of the child has an
autoimmune disease, such as
ξ Some types of congenital or
structural heart disease
ξ Heart muscle disease
ξ Genetic abnormality
How it is Diagnosed?
A member of the health care team does a
complete exam and a health history.
An electrocardiogram (ECG or EKG)
is done to look at the heart’s electrical
activity. Normal numbers for the heart’s
electrical conduction system depend on
your child’s age. Electrical conduction in
the heart gradually slows with age.
A Holter monitor is a 24 or 48 hour
recording done to help evaluate the
heart’s conduction system.
An exercise treadmill test may be
performed in older children and
An echocardiogram is an ultrasound of
the heart and may be done to assess heart
structure and function.
How is it Treated?
It depends on the cause of the heart
block. Some children who have
complete heart block may need surgery
to place a permanent pacemaker to
regulate the heart rate. Your child’s
health care team will discuss the testing
and treatment of your child’s heart
Who Do I Call With Questions?
Your child’s doctor, nurse or clinic staff
can answer your questions. Our phone
number is (608) 263-6420. Ask for
AFCH Pediatric Cardiology Website:
Your health care team may have given you this information as part of your care. If so, please use it and call
if you have any questions. If this information was not given to you as part of your care, please check with
your doctor. This is not medical advice. This is not to be used for diagnosis or treatment of any medical
condition. Because each person’s health needs are different, you should talk with your doctor or others on
your health care team when using this information. If you have an emergency, please call 911. Copyright ©
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