Mechanism of Prolongation of the R-R Interval with Electrical Stimulation of the Carotid Sinus Nerves in Man
Why the study?
Does electrical stimulation of the carotid sinus nerves prolong the R-R interval via parasympathetic activity in patients with implanted stimulators?
Population
8 patients with an implanted carotid sinus nerve stimulator
Comparison
Activation of an implanted carotid sinus nerve… vs Baseline (prior to autonomic blocking drugs)
Design
Case_series
Authors
Discussion
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Implication
May indicate parasympathetic mediation of carotid sinus stimulation effects on R-R interval; hypothesis-generating from a single case.
Key Points
- The aim is to understand how stimulation of the carotid sinus nerves affects the R-R interval in varying autonomic states.
- Studied eight patients with implanted carotid sinus nerve stimulators under different autonomic conditions.
- Induced beta-receptor blockade with propranolol (0.20 mg/kg) and parasympathetic blockade with atropine (0.04 mg/kg).
- Measured changes in R-R interval in supine and standing positions as well as during treadmill exercise.
- R-R interval prolonged by 269 ± 56 msec before autonomic blockade, 442 ± 214 msec after propranolol (NS), and 44 ± 13 msec after both drugs (P < 0.025).
- During exercise, R-R interval increased by only 40 ± 30 msec before blockade, 62 ± 19 msec after propranolol, and 40 ± 30 msec after both drugs.
Structured PICO
Does electrical stimulation of the carotid sinus nerves prolong the R-R interval via parasympathetic activity in patients with implanted stimulators?
P
Population
8 patients with an implanted carotid sinus nerve stimulator
I
Intervention
Activation of an implanted carotid sinus nerve stimulator under varying levels of background autonomic activity and efferent autonomic blockade (intravenous propranolol 0.20 mg/kg and intravenous atropine 0.04 mg/kg)
C
Comparator
Baseline (prior to autonomic blocking drugs)
O
Outcome
Prolongation of the R-R intervalsurrogate
Prolongation of the R-R interval produced by carotid sinus nerve stimulation is primarily mediated by augmented parasympathetic activity, which is attenuated during exercise.
Cite This Study
Eckberg et al. (1972) studied this question.