HF 7629

First Degree and Second Degree Mobitz Type 1 (or Wenckebach) Heart Block in Your Child

Normal Heart

The heart works like an electrical pump. The sinoatrial (SA) or sinus node controls the heart rate. The sinus node sends an electric signal to the top chambers of the heart called the atria causing them to contract. The atrioventricular (AV) node sends the signal to the lower chambers of the heart called ventricles, causing them to contract.

First Degree Heart Block

First degree heart block is a delay in sending the signal between the SA node and the ventricles. First degree AV block can be normal if it happens at rest or during sleep. The time it takes to send the signal from the SA node to the ventricles should shorten during exercise or with increased heart rates. With first degree AV block every atrial beat sends a signal to the ventricles. Your heart doctor may suggest more tests and clinic visits.

Second Degree Mobitz Type I (or Wenckebach)

Wenckebach is a gradual delay in sending the electrical signal from the SA node to the ventricles with each beat until there is a single dropped beat. This type of heart block may be normal during rest or sleep, but is not normal at increased heart rates or during exercise. Your heart doctor may suggest more tests and clinic visits.

Signs and Symptoms

Most infants and children have no signs or symptoms of first degree AV block or Wenckebach.


A member of the health care team does a complete exam and a health history.

Your child will have an ECG or EKG to look at how the heart is working. Normal numbers depend on your child’s age. Your heart slows over time as you age.

A Holter monitor records the heart for 24 or 48 hours to look the heart’s electrical system.

Who to Call

Your child’s doctor, nurse, or clinic staff can answer any questions. Our phone number is (608) 263-6420. Please ask for Pediatric Cardiology.

AFCH Pediatric Cardiology Website: www.uwhealth.org