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.
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 CCAVBpatients 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 CCAVBpatients despite maximal effort (respiratory exchange ratio 1.2 ± 0.1). EF was augmented with exercise in controls but not in CCAVBpatients (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.