Study objectives: Patients with chronic heart failure and implanted cardioverter-defibrillators (ICDs) may have a higher incidence of new-onset or worsening heart failure requiring hospitalization with dual-chamber ICDs compared with single-chamber ICDs.
Design and setting: The purpose of this study was to show the impact of permanent right ventricular (RV) pacing on exercise capacity and related cardiorespiratory parameters in patients with chronic heart failure and ICDs.
Patients and interventions: Seventeen patients with chronic heart failure and a dual-chamber ICD performed cardiopulmonary exercise testing (CPX) on 3 different days. After CPX 1, patients were randomized either to back-up pacing or permanent RV pacing. After 3 months, CPX 2 was performed and patients changed groups (crossover design); CPX 3 was performed after 3 additional months.
Measurements and results: Maximal values for workload (108 ± 46 W vs 117 ± 48 W, p < 0.01), oxygen uptake (V̇o2) [21.0 ± 5.3 mL/min/kg vs 22.5 ± 6.4 mL/min/kg, p < 0.05], oxygen pulse (13 ± 3.7 mL vs 14 ± 4.0 mL, p < 0.05), and metabolic equivalent (6.0 ± 1.5 vs 6.4 ± 1.8, p < 0.05) were significantly lower with permanent RV pacing compared to back-up pacing. Workload, V̇o2, and oxygen pulse were significantly reduced at the ventilatory anaerobic threshold, while workload and V̇o2 were significantly lower at the respiratory compensation point. No differences were found for maximal heart rate, minute ventilation V̇e, and respiratory exchange ratio. The V̇e/carbon dioxide production slope was significantly steeper with permanent RV pacing compared to back-up pacing.
Conclusions: Permanent RV pacing significantly reduced maximal and submaximal measures of exercise. For patients with chronic heart failure and sufficient atrioventricular conduction, every effort should be made to minimize permanent right ventricular pacing.