Diminished exercise capacity and chronotropic incompetence in pediatric patients with congenital complete heart block and chronic right ventricular pacing.
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).


CONCLUSION
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.
['Motonaga|Kara S|KS|', 'Punn|Rajesh|R|', 'Axelrod|David M|DM|', 'Ceresnak|Scott R|SR|', 'Hanisch|Debra|D|', 'Kazmucha|Jeffrey A|JA|', 'Dubin|Anne M|AM|']
D000293:Adolescent D002304:Cardiac Pacing, Artificial D002648:Child D002675:Child, Preschool D004452:Echocardiography D005080:Exercise Test D017079:Exercise Tolerance D005260:Female D005500:Follow-Up Studies D006327:Heart Block D006339:Heart Rate D006352:Heart Ventricles D006801:Humans D008297:Male D010138:Pacemaker, Artificial D011446:Prospective Studies D016896:Treatment Outcome D016277:Ventricular Function, Left
exercise Chronotropic incompetence Congenital complete atrioventricular block