Cardiopulmonary Exercise Testing in DDD Compared to VYI Pacing Modes

To compare the effect of DDD and VVI pacing modes on exercise cardiopulmonary performance, 10 patients underwent rest and exercise first-pass radionuclide angiography in conjunction with gas exchange analysis in one pacing mode first, and 1 week later in the other mode. There were 9 males and 1 female, ages 50-79 years (mean 66). All patients had complete heart block with intact sinus mechanism. Of the 10 patients, 4 had clinical symptoms compatible with the pacemaker syndrome while in VVI. All 4 patients with pacemaker syndrome reported subjective improvement while in DDD mode. Compared with VVI mode, patients in DDD mode demonstrated a larger increase in heart rate (p < 0.001) and in oxygen uptake (p < 0.05) with exercise. There was no significant difference in peak workload, exercise duration, and peak systolic blood pressure. Both the peak exercise stroke volume and the end-diastolic volume were smaller (p < 0.002 and p < 0.01, respectively). The cardiac output and the ejection fraction increased with exercise in either mode. The cardiac output increase was the same in both modes. The ejection fraction increase was higher in WI than in DDD mode (p < 0.01). The subjective improvement in those patients with pacemaker syndrome by DDD pacing did not correlate with any measured parameter. In conclusion, cardiac output increases with exercise in both modes in different ways. In DDD mode the increase was mainly due to the heart rate increase, whereas in WI the increase was mainly due to the stroke volume increase.