Arrhythmias caused by a disruption of the electrical signals in the heart called heart blocks can occur in infants as a result of congenital heart defects or acquired disease or damage. The signs, symptoms and prognosis for infants with heart block vary greatly with the type and severity of disease, ranging from conditions that may produce no overt complications to medical emergencies.
Features
The heart contains four chambers: two atria and two ventricles. In a normal heart, the electrical activity originates from a small piece of tissue in the right atrium and then spreads through pathways to the rest of the atrial tissue and ventricles to cause muscular contraction. Heart block describes a condition leading to a disruption of this electrical communication between the atria and the ventricles. This disruption in electrical signal leads to an arrhythmia, or problem with the hearts rhythm or rate.
Types
Heart blocks are classified as 1st, 2nd or 3rd degree. Severity increases from 1st to 3rd based on the disruption of the electrical signal in the heart. Heart blocks in the 1st and 2nd degree categories describe conditions in which the signal from the atria to the ventricles of the heart is slowed or partially blocked. In a 3rd degree heart block, there is no communication between the atria and ventricles resulting in complete heart block and a potentially serious arrhythmia. Infants with 3rd degree heart block will not effectively circulate blood and will require immediate intervention.
Congenital Heart Block
Most cases of heart block in infants result from congenital heart blocks or cardiac defects. Congenital heart defects are the most common type of birth defect, affecting as many as eight out of every 1,000 births. Even minor heart defects can lead to a heart block, or disruption of electrical signals in the heart.
Maternal autoimmune disease such as lupus increases the risk for congenital heart block. In lupus, maternal antibodies can cross to the developing baby and impair normal development of the heart. Most other causes of congenital heart block have no directly identifiable cause.
Acquired Heart Block
Acquired heart blocks result from damage to the heart or disease. While acquired heart blocks occur more frequently in adults, exposure to toxic substance, certain drugs and infections can cause acquired heart blocks in infants.
Outlook
The symptoms and outcome from heart block depend in the type and severity. First degree heart blocks rarely cause any complications. Second degree heart blocks can produce a range of effects from minimal impact to dizziness and fainting. Third degree heart blocks impair the ability of the heart to effectively circulate blood to the rest of the body and require medical attention and treatment. Treatment for 3rd degree, or complete, heart blocks utilizes pacemaker implantation to maintain a normal ventricular heart rate.
