Objective To estimate the effects of long term right ventricular apical pacing on cardiopulmonary functions in patients with normal heart function.

Method A total of 30 patient underwent dual-chamber pacemaker implantation with normal heart function (LVEF>55%, NYHA classification I–II) were enrolled and divided into two groups according to the percentage of ventricular pacing (VP), VP≤45% group (n=16) and VP>45% group (n=14). Patients with disease of respiratory, nervous or motor systems were excluded. Cardiopulmonary exercise test (CPET) was performed in all patients. We recorded the peak oxygen uptake (VO₂ peak), anaerobic threshold (AT), ventilatory response (VE/VCO₂ slope) and other parameters during the exercise. Left ventricular ejection fraction (LVEF), left ventricular end diastolic dimension (LVEDd), left ventricular end-diastolic volume (LVEDV), systolic volume and E/A were measured using echocardiography before and after the pacemaker implantation.

Results There were no significant differences in baseline characteristics between the two groups. The meantime of enrollment after pacemaker implantation was 5.8 years. Cardiopulmonary function was significantly better in VP≤45% group than VP>45% group. Independent-samples t-testing showed a significantly higher VO₂ peak (19.8±3.3 ml/kg·min vs 17.5±2.5 ml/kg·min, p=0.047) and AT (18.5±1.4 ml/kg·min vs 16.6±2.3 ml/kg·min, p=0.038) in VP≤45% group than VP>45% group. While VE/VCO₂ slope (31.4±3.0 vs 35.1±5.9, p=0.04) was significantly lower in VP≤45% group than VP>45% group. But there were no significant differences with respect to the LVEF and other echocardiography parameters between the two groups.

Conclusion Long Term right ventricular apical pacing is associated with the deterioration of cardiopulmonary function in patients with normal heart functions. Cardiopulmonary exercise test is a sensitive diagnostic method to show the early changes of cardiac function.