Optimal maximum tracking rate of dual-chamber pacemakers required by children and young adults for a maximal cardiorespiratory performance.
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.
Mathony
U
U
University Department of Pediatric Cardiology, Martin-Luther-University Halle-Wittenberg, Halle. uwe.mathony@medizin.uni-halle.de
Schmidt
Hendrik
H
Gröger
C
C
Francis
Darrel P
DP
Konzag
I
I
Müller-Werdan
Ursula
U
Werdan
Karl
K
Syska
Joachim
J
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