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Arterial baroreflex control of the sinus node during dobutamine exercise stress testing
P van de Borne1, S Heron, H Nguyen
1Hypertension Clinic, Department of Intensive Care, Erasme Hospital, Brussels, Belgium. pvandebo@ulb.ac.be
Hypertension (Dallas, Tex. : 1979)
|April 16, 1999
Summary
Dobutamine infusion impairs arterial baroreflex sensitivity during simulated exercise. This impairment is linked to altered operating points of arterial baroreceptors and direct adrenergic stimulation effects on the sinus node.
Area of Science:
- Cardiovascular Physiology
- Exercise Physiology
- Autonomic Nervous System Function
Background:
- The precise impact of catecholamines, central command, and muscle afferents on baroreflex control during exercise remains incompletely understood.
- Understanding these factors is crucial for interpreting cardiovascular responses during physical activity and stress testing.
Purpose of the Study:
- To investigate the isolated effects of dobutamine-induced hemodynamic changes on baroreflex control of the sinus node.
- To differentiate the roles of catecholamines versus central command and muscle afferents in exercise-induced baroreflex alterations.
Main Methods:
- A dobutamine infusion protocol was used in 13 healthy subjects to mimic moderate exercise hemodynamics without central command or muscle afferent activation.
- Hemodynamic parameters (systolic blood pressure, RR interval) and their variability were measured, alongside arterial baroreflex sensitivity (BRS).
Main Results:
- Dobutamine increased systolic blood pressure and heart rate (shortened RR interval), while increasing systolic blood pressure variability but decreasing RR interval variability.
- Arterial baroreflex sensitivity significantly decreased from 12+/-2 to 3+/-1 ms/mm Hg.
- Greater systolic blood pressure increases correlated with more pronounced reductions in BRS, and dobutamine's chronotropic effects blunted reflex bradycardia.
Conclusions:
- Arterial baroreceptor operating point shifts and adrenergic stimulation impair baroreflex control of the sinus node during dobutamine-induced hemodynamic changes.
- Baroreflex control is not reset when exercise hemodynamics are replicated without central command or muscle afferent input.