Paroxysmal atrioventricular block in young patients

A 1-year-old boy with long pauses caused by paroxysmal atrioventricular block and sinus arrest: Vagal reflex and effect of pacing

Paroxysmal atrioventricular block (PAVB) is rare in children. A 1-year-old boy presented with PAVB and sinus arrest that resulted in refractory life-threatening symptomatic long pauses. Continuous heart rate variability analysis with high time resolution (wavelet analysis) revealed an abrupt increase in parasympathetic activity just before a long pause, which indicated a vagal reflex. Although a pacemaker is not always effective because of a concomitant vasodepressive response in such cases, the complete stabilization after pacemaker implantation in this case supports the necessity and usefulness of pacemaker implantation in patients with reflex-induced highly symptomatic bradycardia.

Complete paroxysmal atrioventricular block in a 2-year-old girl

We present a case of atypical syncope in a 2-year-old, otherwise healthy girl. The patient presented with three episodes of syncope without any precipitating factors and no family history of sudden unexpected death. Holter monitoring revealed 24 events of complete atrioventricular block lasting up to 6 seconds. A normal 12-lead electrocardiogram does not necessarily exclude cardiac disease, and Holter monitoring is warranted in children with atypical syncope.

Paroxysmal atrioventricular block

Paroxysmal atrioventricular block (AVB) is a poorly defined clinical entity characterized by abrupt and unexpected change from 1:1 atrioventricular conduction to complete heart block, leading to syncope and potential sudden cardiac death. Although a dangerous condition because of unreliable escape mechanism, proper diagnosis of paroxysmal AVB is often missed and overlooked because of its unfamiliarity, unpredictability, and in some cases, no clear evidence of atrioventricular conduction disease during normal 1:1 conduction.

Ventricular pacing threshold variations in the young

Ventricular Capture Management (VCM) is a Medtronic Kappa pacemakers (PM) feature that automatically measures pacing threshold through detection of the evoked response after a pacing stimulus. The aim of this study was to evaluate the range of variation of ventricular pacing threshold in pediatric patients with endocardial and epicardial pacing leads. Thirty-one patients (median age 6.5 years) were implanted with a Kappa 901 PM for atrioventricular block or sinus node dysfunction. Congenital heart defects (CHD) were present in 58% of patients. Ventricular leads were epicardial in 52% of patients. VCM was programmed to automatically measure threshold every 2 hours. In a median follow-up of 12 months, 27,110 threshold measurements, 72% of which were successful, have been taken in 94% of patients. Measurement success was 99% in the endocardial leads group (age at implantation 12 +/- 6 years) and 31% in epicardial leads (age 4 +/- 5 years) (P < 0.05). Main reasons for unsuccessful measurements were high heart rate and, in a patient with an endocardial lead, competition with intrinsic rhythm. Undersensing or oversensing of the evoked responses was not detected. In all successful VCM measurements, epicardial pacing and CHD contributed to stability of thresholds (multivariate analysis). Pacing threshold showed specific circadian patterns: higher thresholds were found between 00.00 and 06.00 a.m., but the variation was low, 0.03 +/- 0.01 V. In conclusion, children and young patients show stable ventricular thresholds, especially in presence of CHD, and epicardial leads are at least as stable as endocardial leads. Ventricular pacing threshold showed a circadian variability similar to that described in adults, that does not seem to influence VCM functioning and PM programming.