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Limitations of Rate Response of an Activity‐Sensing Rate‐Responsive Pacemaker to Different Forms of Activity
Author(s) -
LAU CHUPAK,
MEHTA DAVENDRA,
TOFF WILLIAM D.,
STOTT ROLLIN J.,
WARD DAVID E.,
CAMM A. JOHN
Publication year - 1988
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.1988.tb04535.x
Subject(s) - medicine , cardiology
The responses of an activity‐sensing rate‐responsive system (Activitrax) to various forms of physiological activity were assessed in 15 individuals who had this pacemaker. Nine were patients with complete heart block and atrial arrhythmias; their mean age was 60 years (range, 41–85 years). Six were age‐matched healthy volunteers who were exercised with an external Activitrax system attached firmly to the chest wall. The pacemaker was programmed to achieve a pacing rate of about 100 bpm at the end of the first stage of the Bruce protocol (pacemaker settings; rate = 70–150 bpm; threshold = low to medium; response = 6–9). In the activity‐sensing ventricular pacing mode, oil patients achieved a significant increase in treadmill time compared to constant‐rate ventricular pacing (mean ± SD, 8.0 ± 3.3 vs 5.4 ± 2.3 minutes; p < 0.01), with a mean maximum pacing rate of 123 ± 18 bpm. Jogging in place produced a prompt increase in pacing rate, with the maximum achieved at the end of the exercise. However, physiological activities such as hand‐grip, the Valsalva maneuver and standing resulted in only minimal rate response. Pacing rate after ascending 4 flights of stairs was the same as that achieved after descending the same stairs (100 ± 8 vs 105 ± 4 bpm; p < 0.1). All 15 subjects were exercised from resting heart rate for 3 minutes on a treadmill at 1.2 mph and 2.5 mph with four gradients at each speed. Although the pacing rate increased with a faster treadmill speed (p < 0.005), it did not respond appropriately to a change in gradient compared to the sinus rate. We conclude that although activity‐sensing rate‐responsive pacing gives a prompt increase in pacing rate and improves maximum exercise tolerance, further refinement is necessary because: (1) physiological activities not associated with significant movement are not detected by this pacing system; (2) detection of vibrations as an indicator of activities does not correlate well with the level of exertion.