title: Optimal maximum tracking rate of dual-chamber pacemakers required by children and young adults for a maximal cardiorespiratory performance.
abstract: BACKGROUND
  Children and young adults require a higher maximum tracking rate (MTR) for physical activity. The objective of the present study was to observe whether higher MTR of 170 or 190 beats per minute (bpm) have a positive impact on the maximal cardiorespiratory capacity of children and young adults in comparison with a lower MTR of 140 bpm.
  
  
  METHODS
  Fifteen patients with atrioventricular block and normal sinus-node chronotropic function (age 7-24 years) with DDD- (14) or VDD-pacemakers (PM) (1) were enrolled. First, the MTR was adjusted to 140 bpm for 6 weeks and elevated in a second step to 170 or 190 bpm. At the end of each period two cardiopulmonary exercise tests, a 24-hour ECG and a PM test were performed.
  
  
  RESULTS
  All patients increased their maximal heart rate (139.0 +/- 1.0 vs 177.0 +/- 10.0 bpm, P < 0.001), peak cardiorespiratory capacity (2.4 +/- 0.6 vs 2.8 +/- 0.7 W/kg, P < 0.001), peak oxygen uptake (28.3 +/- 7.0 vs 35.7 +/- 9.5 mL/kg/min, P < 0.005), and oxygen uptake (23.7 +/- 7.4 vs 29.3 +/- 8.4 mL/kg/min, P < 0.02) at the anaerobic threshold. There were no evident heart rhythm disturbances with elevated MTR. Patients with a Wenckebach behavior of the PM had an attenuated increase of maximal cardiorespiratory performance.
  
  
  CONCLUSIONS
  Children and young adults with DDD-/VDD-PM benefit from an elevated MTR by an increased cardiorespiratory capacity, without having more heart rhythm disturbances. A Wenckebach behavior of the PM should be avoided.
authors.affiliation: University Department of Pediatric Cardiology, Martin-Luther-University Halle-Wittenberg, Halle. uwe.mathony@medizin.uni-halle.de
authors.forename: U
authors.initials: U
authors.lastname: Mathony
authors.forename: Hendrik
authors.initials: H
authors.lastname: Schmidt
authors.forename: C
authors.initials: C
authors.lastname: Gröger
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
authors.forename: I
authors.initials: I
authors.lastname: Konzag
authors.forename: Ursula
authors.initials: U
authors.lastname: Müller-Werdan
authors.forename: Karl
authors.initials: K
authors.lastname: Werdan
authors.forename: Joachim
authors.initials: J
authors.lastname: Syska
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D004562:Electrocardiography; D004867:Equipment Design; D005080:Exercise Test; D006327:Heart Block / Q000503:physiopathology / Q000628:therapy; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D010101:Oxygen Consumption / Q000502:physiology*; D010138:Pacemaker, Artificial