Paroxysmal AV Block in Children with Normal Cardiac Anatomy as a Cause of Syncope

Background: Syncope due to episodes of paroxysmal atrioventricular (AV) block, defined as transient advanced second or third‐degree block, is rarely reported in pediatric patients without congenital heart disease. Methods: We reviewed our institutional arrhythmia database from January 1988 to January 2007 to identify all patients less than 18 years of age with normal cardiac anatomy and episodes of syncope associated with paroxysmal AV block. Demographic and clinical information was collected. Results: Six patients were identified ( Table I ). Five of the six patients were female, with an average age of 9.3 ± 4.4 years. Patients had episodes of syncope for an average of 5.6 ± 3.3 years prior to diagnosis. All patients had normal physical examinations, electrocardiograms, and echocardiograms. None were on medications known to interfere with AV nodal function, and laboratory evaluation including Lyme titers were negative. Five of the six patients' episodes were atypical for vasovagal syncope (except patient 6). All patients had documented paroxysmal AV block on either inpatient cardiac monitor, Holter monitor, or event recorder at the time of syncope. There was maintenance or acceleration of the sinus rate during episodes of syncope in all patients (mean atrial rate 107 ± 37 bpm). All six patients had permanent transvenous pacemakers implanted with resolution of symptoms over a mean follow‐up of 5.2 ± 6.3 years. Characteristics of Six Patients with Paroxysmal AV Block Patient Age (years) Sex Medical History Preceding Symptoms Length of Symptoms (years) Method of Diagnosis Atrial Rate with AV Block (bpm) Longest Pause (sec) Pacing Mode Follow‐up (years) 1 2.5 F None Crying out, headache 5 Event recorder 150 17 VVI 0.5 2 8 F ADHD, asthma Nausea, syncope while lying flat 6 Cardiac monitor 115 22 VVI 1.75 3 8 F None Nausea, syncope while lying flat 4 Cardiac monitor 75 11 VVI 16 4 9 F None Crying out, abdominal pain 7 Cardiac monitor 150 14 DDD 10 5 13 M ADHD Blurry vision and room spinning while eating 1 Event recorder 75 7 DDD 1.6 6 15 F None Strong emotion, sight of blood 11 Holter monitor 75 16 DDD 1.5 ADHD = Attention Deficit Hyperactivity Disorder. Conclusion: Paroxysmal AV nodal block is a rare finding in pediatric patients, but should be considered as a possible etiology in patients presenting with episodes atypical for vasovagal syncope. Pacemaker therapy prevented future episodes in all six of our patients.