Third Degree Atrioventricular Block in Children

Atrioventricular (AV) block is defined as a delay or interruption in the transmission of an impulse from the atria to the ventricles due to an anatomical or functional impairment in the conduction system. The conduction disturbance can be transient or permanent. In third degree AV block, also referred to as complete heart block, there is complete dissociation of the atrial and ventricular activity. Atrioventricular block is considered to be “congenital” when it occurs spontaneously in a fetus or young child. In children, the most common cause of permanent acquired complete AV block is surgery for congenital heart disease. Injury to fetal conduction tissues caused by transplacental exposure to maternal autoantibodies related to systemic lupus erythematosus or Sjogren’s syndrome is responsible for 60 to 90 percent of cases of congenital CHB overall1-3. As many as 40 percent of cases of congenital CHB do not present until later in childhood (mean age five to six years). Only rarely do these patients (5 percent) have proven autoimmune etiology. The increased risk of sudden death is associated with the onset of deep bradycardia or ventricular arrhythmia. A routine electrocardiogram is sufficient to diagnose the disease. A 15-year-old girl has been examined at the emergency pediatric outpatient clinic of the University Hospital Centre “Sestre Milosrdnice” for recurrent episodes of presyncope. Physical examination revealed no major deviations other than bradycardia. Her vital signs were within the reference range, with the exception of a pulse of about 44 beats per minute. The electrocardiogram showed atrioventricular dissociation consistent with third degree atrioventricular block. The echocardiogram showed a structurally normal heart except for sinus bradycardia. The girl underwent permanent epicardial pacemaker implantation after which there were no symptoms.