Multisensor rate adaptive pacing: Comparison of different pacing modes by monitoring respiratory parameters

Multisensor rate response was assessed in two groups of patients by monitoring heart rate (HR) and respiratory parameters. Vitatron Saphir II VDD/R dual sensor QT and Activity (ACT) pacemakers were implanted in the group 1 patients (4 men, and 1 woman aged 64 ± 12 years; ejection fraction (EF) 43 ± 6%) who had 2nd or 3rd degree AV block and normal sinus chronotropism. Vitatron Diamond II DDDR dual sensor QT and ACT pacemakers were implanted in the group 2 patients (3 men and 2 women aged 69 ± 4 years, EF 51 ± 5%) with chronotropic incompetence of the sinus node. During treadmill exercise HR (bpm), oxygen uptake (VO₂, ml/kg/min), O₂ pulse, carbon dioxide production, minute ventilation and respiratory exchange ratio were recorded. In group 1, the maximum HR in the VDD mode (137 ± 4 bpm) better matched ACT (134 ± 9 bpm) than QT driven (111 ± 30 bpm) or QT = ACT driven VVIR pacing (112 ± 22 bpm). VO₂ at maximum exercise in the QT mode (22.4 ± 2.4 ml/kg/min) and the QT = ACT mode (25.8 ± 4.8 ml/kg/min) most closely matched with the VDD mode (24.5 ± 3.6 ml/kg/min). In group 2 both HR and VO₂ were significantly higher in the DDDR mode than in the DDD mode during each phase of exercise. In conclusion a correct comparison of sensor based VVIR modes with the VDD mode should be done by analysing respiratory parameters; when comparing DDD and DDDR atrial synchronous modes, evaluation of the HR trend is sufficient.