title: Diminished exercise capacity and chronotropic incompetence in pediatric patients with congenital complete heart block and chronic right ventricular pacing.
abstract: BACKGROUND
  Chronic right ventricular (RV) pacing has been associated with decreased exercise capacity and left ventricular (LV) function in adults with congenital complete atrioventricular block (CCAVB), but not in children.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the exercise capacity and LV function in pediatric patients with CCAVB receiving chronic RV pacing.
  
  
  METHODS
  We prospectively evaluated pediatric patients with isolated CCAVB receiving atrial synchronous RV pacing for at least 5 years. Supine bicycle ergometry was performed, and LV ejection fraction (EF) was evaluated by echocardiography.
  
  
  RESULTS
  Ten CCAVB subjects and 31 controls were matched for age, gender, and body surface area. CCAVB subjects had normal resting EF (63.1% ± 4.0%) and had been paced for 7.9 ± 1.4 years. Exercise testing demonstrated reduced functional capacity in CCAVB patients compared to controls with a lower VO₂peak (26.0 ± 6.6 mL/kg/min vs 39.9 ± 7.0 mL/kg/min, P <.001), anaerobic threshold (15.6 ± 3.9 mL/kg/min vs 18.8 ± 2.7 mL/kg/min, P = .007), and oxygen uptake efficiency slope (1210 ± 406 vs 1841 ± 452, P <.001). Maximum heart rate (165 ± 8 bpm vs 185 ± 9 bpm, P <.001) and systolic blood pressure (159 ± 17 mm Hg vs 185 ± 12 mm Hg, P <.019) also were reduced in CCAVB patients despite maximal effort (respiratory exchange ratio 1.2 ± 0.1). EF was augmented with exercise in controls but not in CCAVB patients (13.2% ± 9.3% vs 0.2% ± 4.8% increase, P <.001).
  
  
  CONCLUSIONS
  Clinically asymptomatic children with chronic RV pacing due to CCAVB have significant reductions in functional capacity accompanied by chronotropic incompetence and inability to augment EF with exercise.
authors.affiliation: Stanford University, Palo Alto, California. Electronic address: sachie@stanford.edu.
authors.forename: Kara S
authors.initials: KS
authors.lastname: Motonaga
authors.affiliation: Stanford University, Palo Alto, California.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Punn
authors.affiliation: Stanford University, Palo Alto, California.
authors.forename: David M
authors.initials: DM
authors.lastname: Axelrod
authors.affiliation: Stanford University, Palo Alto, California.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Ceresnak
authors.affiliation: Lucile Packard Children's Hospital Stanford, Palo Alto, California.
authors.forename: Debra
authors.initials: D
authors.lastname: Hanisch
authors.affiliation: Lucile Packard Children's Hospital Stanford, Palo Alto, California.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Kazmucha
authors.affiliation: Stanford University, Palo Alto, California.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Dubin
mesh_terms: D000293:Adolescent; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects*; D002648:Child; D002675:Child, Preschool; D004452:Echocardiography; D005080:Exercise Test / Q000706:statistics & numerical data; D017079:Exercise Tolerance; D005260:Female; D005500:Follow-Up Studies; D006327:Heart Block / Q000151:congenital* / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy; D006339:Heart Rate; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D008297:Male; D010138:Pacemaker, Artificial / Q000009:adverse effects*; D011446:Prospective Studies; D016896:Treatment Outcome; D016277:Ventricular Function, Left
keywords: Chronotropic incompetence; Congenital complete atrioventricular block; exercise