November 1, 1994Psychophysiology
Autonomic cardiac control. II. Noninvasive indices and basal response as revealed by autonomic blockades
Why the study?
Do noninvasive indices like preejection period and high frequency heart rate variability accurately reflect sympathetic and vagal influences on the heart under autonomic blockades?
Population
Female subjects
Comparison
Metoprolol or atropine sulfate infused for 15… vs Saline infusion
Design
RCT, double-blind
Follow-up
3 consecutive days
Authors
Discussion
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Implication
PEP and HF-HRV can serve as selective noninvasive autonomic markers in practice; confirms their dissociation under blockade in this RCT.
Key Points
- To determine the specificity of noninvasive cardiovascular indices in reflecting sympathetic and vagal cardiac regulation during baseline and orthostatic stress.
- Double-blind pharmacological study in female subjects tested across three consecutive days with infusions of saline, metoprolol (14 mg), atropine sulfate (2 mg), and dual blockade.
- Cardiovascular metrics—including preejection period (PEP), heart period, high-frequency heart rate variability (HF HRV, 0.12–0.40 Hz), and blood pressure—were measured during sitting and standing postures.
- Preejection period (PEP) selectively reflected sympathetic cardiac influence without vagal contamination, whereas high-frequency heart rate variability (respiratory sinus arrhythmia) selectively reflected vagal influence.
- Postinfusion baseline PEP under saline predicted individual differences in sympathetic activation, while postinfusion heart period predicted individual differences in vagal activation.
Structured PICO
Do noninvasive indices like preejection period and high frequency heart rate variability accurately reflect sympathetic and vagal influences on the heart under autonomic blockades?
P
Population
Female subjects
I
Intervention
Metoprolol (14 mg) or atropine sulfate (2 mg) infused for 15 min, with orthostatic stressor (standing versus sitting postures)
C
Comparator
Saline infusion
O
Outcome
Noninvasive indices of autonomic cardiac control including preejection period (PEP) and high frequency (HF, 0.12-0.40 Hz) heart rate variabilitysurrogate
Preejection period and high-frequency heart rate variability serve as specific noninvasive indices of sympathetic and vagal cardiac influences, respectively.
Cite This Study
Cacioppo et al. (1994) studied this question.