title: Circadian pattern of atrial pacing threshold in the young.
abstract: OBJECTIVE
  The aim of this study was to evaluate the circadian variation of atrial pacing threshold in young patients.
  
  
  RESULTS
  Atrial Capture Management (ACM) algorithm is a Medtronic EnPulse pacemaker (PM) feature that uses two algorithms: atrioventricular conduction (AVC) (atrial pacing and spontaneous AVC) and atrial chamber reset (ACR) [intrinsic atrial activity with atrioventricular block (AVB)]. For this prospective, non-randomized study, ACM automatically measured and recorded thresholds every 4 h. Data are reported as median (range) or mean +/- SD. In 2004-05, 14 consecutive patients (11 males, 79%), aged 12 years (1 day-24 years) received an EnPulse DDD/R PM for AVB (eight patients, 57%) or sinus node dysfunction. A new pacing system was implanted in eight patients (57%) and a replaced PM in six patients. Epicardial leads were implanted in 10 patients (71%). The follow-up duration is 11 (1-18) months: 9742 threshold measurements were attempted (6328 AVC, 3414 ACR), of which 3797 (39%) were successful (1807 AVC, 29%, 1990 ACR, 58%) in 11 (79%) patients. Three infants had no successful measurements. Measurement success was 42 +/- 34% (AVC 27 +/- 39%, ACR 41 +/- 29%). Higher thresholds were found between 00.00 and 12.00 a.m. and lower between 12.00 and 20.00.
  
  
  CONCLUSIONS
  Young patients show a circadian variability of atrial threshold with higher thresholds between 00.00 and 12.00.
authors.affiliation: Dipartimento Medico-Chirurgico di Cardiologia, Ospedale Pediatrico Bambino Gesù, Piazza S. Onofrio 4, 00165 Roma, Italy. silvetti@opbg.net
authors.forename: Massimo S
authors.initials: MS
authors.lastname: Silvetti
authors.forename: Antonella
authors.initials: A
authors.lastname: De Santis
authors.forename: Simona
authors.initials: S
authors.lastname: Marcora
authors.forename: Tiziana
authors.initials: T
authors.lastname: De Santo
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Grovale
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Drago
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001283:Atrioventricular Node / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial; D002648:Child; D002675:Child, Preschool; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006325:Heart Atria / Q000503:physiopathology; D006327:Heart Block / Q000175:diagnosis* / Q000503:physiopathology* / Q000628:therapy; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D010138:Pacemaker, Artificial; D011446:Prospective Studies