Comparison of continuously recorded sensor and sinus rates during daily life activities and standardized exercise testing: efficacy of automatically optimized rate adaptive dual sensor pacing to simulate sinus rhythm.

The normal sinus rhythm remains the gold standard to compare the rate response of a rate adaptive pacemaker. The aim of this study was to assess an automatically optimized dual sensor system by continuous comparison of the normal sinus (SR) and sensor indicated rates (SIR). Twelve patients with complete heart block (mean age 60 +/- 9 years) with normal sinus rhythm received a dual sensor pacemaker driven by combined, automatically adaptive activity and QT sensors. After 1 month of automatic adaptation, patients performed a treadmill exercise in the VDD mode with simultaneous collection of SR and combined SIR. Thereafter the difference between SR and SIR was recorded over a 1-month period using a software downloaded into the pacemakers, with the patients ambulatory during this period. During exercise testing, the SR and SIR were significantly correlated (r = 0.96 +/- 0.02, P < 0.001), and the mean difference between SR and SIR was 4.01 +/- 4.47 beats/min. The percentages of paced beats, over the 1 month ambulatory period, that exhibited a difference between SR and SIR of 8 beats/min were 98% +/- 2%, 90% +/- 4% and 67% +/- 8% for low, medium, and high workloads, respectively (P < 0.05, ANOVA), whereas > 95% of SIR were within 15 beats/min of SR independent of the level of activities. Thus, an automatically programmed dual sensor gives an accurate reflection of SR during exercise. SIR was less accurate for more vigorous daily life activities, but most of the SIR were within the normal SR variation of 15 beats/min.