LONG-TERM CLINICAL-PERFORMANCE OF A CENTRAL VENOUS OXYGEN-SATURATION SENSOR FOR RATE-ADAPTIVE CARDIAC PACING

Rate adaptive ventricular pacemakers using central venous oxygen satur ation (O2Sat) to control the pacing rate have been implanted in 14 pat ients (mean age 71 years), with a mean follow-up period of 44 months ( range 2-63 months). In eight patients the pacemakers were replaced due to signs of battery depletion after an implant duration of 39-58 mont hs. During bicycle exercise testing the O2Sat decreased on average fro m 61% +/- 4% at rest to 36% +/- 4% (P < 0.0001) at peak exercise, and the maximum pacing rate was 122 +/- 5 beats/min. The time delay until the 02Sat had dropped 10%, 65%, and 90% of the total reduction during exercise was 4.8 +/- 0.9 seconds, 39.8 +/- 3.8 seconds, and 71.3 +/- 7 .5 seconds, respectively. The O2Sat decreased 9.4% +/- 2% (P < 0.005) from resting supine to resting sitting. Oxygen breathing increased the telemetered O2Sat from the pacemaker by 8.4 % +/-1% (P <0.001). Durin g follow-up the O2Sats were relatively stable in 50% of the patients, but demonstrated significant fluctuations in the others. At 1-year inv asive follow-up O2Sat measured by the pacemaker decreased 22% +/- 2%, and in blood samples from the right ventricle 22% +/- 2% from rest to 3 minutes exercise at 25 watts, There was a significant correlation be tween O2Sat measured by the pacemaker and in blood samples from right ventricle (n = 105; r = 0.73; P < 0.001). In two patients the O2Sat dr opped significantly during pneumonia. In another patient episodes of a ngina pectoris was associated with low O2Sat and a concomitant fast pa cing rate.