Heart Block in Children

There are three main types of heart block – first degree, second degree (Type I and II), and third degree, Type III. Certain types of heart block can be a "normal" finding in healthy individuals. Highly trained athletes can have first-degree heart block at rest because their heart is so well conditioned by exercise. Even non-athletes can have second-degree heart block during deep sleep from stimulation from the vagus nerve. When a person faints, they may have evidence of temporary heart block. A diagnosis of heart block does not always require your healthcare team to provide a treatment or intervention.

First-Degree AV block - In first-degree block, all signals that originate from the sinus node travel down to the ventricles, but the time for these beats to go across the AV node is consistently longer than accepted normal ranges.

Second-Degree Mobitz I AV block (Wenckebach) - If a patient has Wenckebach (WHEN-key-bock) heart block, the time it takes to conduct consecutive sinus beats to the ventricles becomes longer and longer, until eventually a beat is "dropped," meaning it doesn't reach the ventricles.

Second-Degree Mobitz II AV block - Mobitz II AV block occurs when every now and again one sinus beat is blocked and fails to reach the ventricles. There can be a pattern to the block – for example, every other beat is blocked from the ventricles - or it can be sporadic, with random beats dropping.

Third Degree AV block (Complete Heart Block) - When a patient has complete heart block, the electrical activity of the top and bottom of the heart is not coordinated. It also means the patient may not be able to raise their ventricular heart rate appropriately, even when the body needs the ventricles to pump more blood, such as during exercise or while playing sports.

Except for complete heart block, most AV block does not cause symptoms. However, if the ventricular rate is too slow, symptoms can include:

• Feeding difficulty in infants
• Headaches
• Fatigue
• Dizziness or lightheadedness
• Syncope (fainting or passing out)
• Decreased exercise endurance/tolerance

Patients with third degree heart block may, but do not always, have symptoms at rest. This depends on whether they were born with heart block (called congenital heart block) or they developed heart block after they were born (called acquired heart block). Symptoms also can be affected by the speed of a patient's "escape rhythm," or the rhythm that comes automatically from the bottom of the heart. This rhythm is slower than a rhythm coming from the sinus node and is not as good at responding with a higher heart rate when the body needs the heart to work harder. An escape rhythm may suffice at rest but may not meet the body's demands during activity.

The diagnosis of heart block is made based on specific findings noted on your electrocardiogram (ECG). Specifically, your healthcare team will look at the relationship between the electrical signals from the top of the heart and the electrical signals in the bottom of the heart.

After diagnosing heart block, your healthcare team may order additional testing, such as a Holter monitor to determine the frequency and severity of the heart block. Holter monitors or other long-term monitors can also be used for routine rhythm monitoring or if there are concerns about worsening heart block or symptoms. Another common test following a heart block diagnosis is an exercise stress test, which evaluates whether the heart rate can adapt to the body's needs during activity, especially if the patients has symptoms while exercising.

Some causes of heart block can be reversible.

With more significant heart block, a pacemaker may be necessary. The decision to implant a pacemaker is based on resting heart rate, symptoms, or other information gathered by their healthcare team.