Key result
Ventricular impedance pacemakers linked to ~9 bpm higher heart rate during active standing.
Why the study?
The study aimed to evaluate heart rate adaptation by a pacemaker using ventricular impedance during autonomic challenges in chronotropic incompetent patients.
Does pacemaker rate control using a ventricular impedance signal appropriately adapt heart rate to autonomic stressors in chronotropic incompetent patients?
Observational (n=15)
Does pacemaker rate control using a ventricular impedance signal appropriately adapt heart rate to autonomic stressors in chronotropic incompetent patients?
A closed-loop pacemaker strategy based on ventricular impedance successfully adapts heart rate to autonomic stressors in chronotropic incompetent patients.
Answers are grounded in this paper and cite their sources.
Impedance-based pacing may enable rate adaptation during autonomic stress; leaves open clinical utility pending larger trials.
The aim of this study is to evaluate the heart rate adaptation obtained by a pacemaker, based on a measure of ventricular impedance in patients undergoing autonomic challenges. The evaluation procedure was based on the analysis of the mean value (MV) and heart rate variability (HRV) of RR and systolic pressure intervals, according to a set of neurovegetative stressors (controlled respiration in supine position and during active standing; mental stress; handgrip, and noninvasive sinusoidal stimulation of carotid baroreceptors). Each test lasted 5 minutes. Fifteen chronotropic incompetent patients first implanted, were studied three months after implantation. ECG, respiration activity, and noninvasive blood pressure were monitored. HRV was evaluated by spectral analysis. Variability in the low frequency (LF) and high frequency (HF) bands was compared by computing percentage and absolute powers. We found that baseline HR was 72.2 +/- 5.5 beats/min, in mental stress was 76.8 +/- 7.8 beats/min, in handgrip was 79.2 +/- 6.3 beats/min, and in active standing was 80.9 +/- 8.6 beats/min (P < 0.01, Friedman's test). During active standing, LF component was significantly higher with respect to baseline (25.7% of total power in standing; 9.4% in baseline, P < 0.01) and it was synchronous to the LF component of the arterial pressure variability. Carotid activation/deactivation by neck suction induced synchronous changes in the paced rates. In conclusion, closed loop strategy based on ventricular contractility continuously controls heart rate by tracking the sympathetic modulation to the heart.
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Santini et al. (2004) conducted an observational in Chronotropic incompetence (n=15). Autonomic stressors (active standing, mental stress, handgrip, carotid stimulation) vs. Baseline (supine position) was evaluated on Heart rate adaptation (mean value and heart rate variability) (p=<0.01). Autonomic stressors significantly increased heart rate from a baseline of 72.2 to 80.9 beats/min during active standing (P<0.01) in patients with pacemakers using ventricular impedance signals.
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