Effect of Autonomic Stressors on Rate Control in Pacemakers Using Ventricular Impedance Signal

Abstract

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.

Influence of Patient’s Exercise Tolerance on Exercise Heart Rate in Closed Loop Stimulation vs. Accelerometer-based Rate Adaptive Pacing

“…Although AS is specifically designed to support physical activity associated with thoracic movement, CLS is not inferior for this kind of activity and is superior to AS during other forms of exercise, like cycling, mental exertion, or emotional stress [5][6][7][8][9][10]14]. In the randomized crossover PROVIDE study, twice as many chronotropically incompetent patients preferred CLS over AS [5].…”

“…In the CLS mode, the pacemaker couples the pacing rate to the myocardial contraction dynamics by measuring ventricular impedance variation [6][7][8]. As cardiac contractility is regulated by the autonomic nervous innervation, CLS is integrated into the natural cardiovascular control loop and responds to physical, mental, and emotional stress [5,[7][8][9][10].…”

“…As cardiac contractility is regulated by the autonomic nervous innervation, CLS is integrated into the natural cardiovascular control loop and responds to physical, mental, and emotional stress [5,[7][8][9][10]. …”

“…If the hypothesis turned to be true, it would imply that CLS is not only more sensitive to various kinds of stress [5,[7][8][9][10] but that it is also more specific than AS during physical exertion. The hypothesis was tested at 1 month, using symptom classification made at enrolment (NYHA I-like [higher exercise tolerance] vs. NYHA II-or III-like [lower exercise tolerance]) ( Table 1).…”

Physiological rate adaptation in a child with chronotropic incompetence through closed-loop stimulation using epicardial leads

“…During each session, surface ECG was continuously acquired and stored thanks to a digital ECG recording system (Cardioline, Trento, Italy). Instantaneous heart rate was extracted off-line by using a previously validated R-wave detection algorithm 2 . All the detected beats were then visually inspected to remove/correct misdetections/misclassifications.…”