June 1, 1975Circulation Research
Altered cardiac responsiveness and regulation in the normal cardiac output type of borderline hypertension.
Key result
Borderline hypertensive patients with normal cardiac output exhibited decreased vagal inhibition and reduced cardiac responsiveness to sympathetic stimulation compared to control subjects.
Why the study?
Do patients with borderline hypertension and normal resting cardiac output have altered cardiac autonomic regulation compared to control subjects?
Population
Patients with borderline hypertension and normal resting cardiac index and n=85 control subjects.
Comparison
Pharmacological autonomic testing including… vs 85 control subjects undergoing the same…
Design
Case-control
Authors
Discussion
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Implication
May indicate early autonomic dysregulation in borderline hypertension despite normal output; leaves open causality and need for prospective confirmation.
Key Points
- This study aims to explore the cardiac regulation in patients with borderline hypertension exhibiting normal resting cardiac index.
- 145 patients with borderline hypertension were assessed, comparing 30% with increased and 70% with normal cardiac index against 85 control subjects.
- Cardiac autonomic blockade was achieved using propranolol and atropine to evaluate stroke volume and cardiac index responses.
- Basic parameters were analyzed, including central blood volume and heart rate response to isoproterenol infusion.
- Patients with normal cardiac index showed significantly lower stroke volume and cardiac index compared to control subjects after autonomic blockade.
- Decreased responsiveness to sympathetic stimulation was observed, indicated by a lower increase in cardiac index following isoproterenol infusion.
- Central blood volume remained normal despite lower stroke volume, suggesting unique mechanisms of cardiac regulation in these patients.
Study Design
Type
Observational (n=230)
Structured PICO
Do patients with borderline hypertension and normal resting cardiac output have altered cardiac autonomic regulation compared to control subjects?
P
Population
145 patients with borderline hypertension (focusing on those with normal resting cardiac index) and 85 control subjects.
E
Exposure
Pharmacological autonomic testing including atropine injection, complete cardiac autonomic blockade (propranolol and atropine), and isoproterenol infusion.
C
Comparator
85 control subjects undergoing the same physiological testing.
O
Outcome
Changes in cardiac index (QI), stroke volume, and heart rate in response to autonomic blockade and sympathetic stimulation.surrogate
Even when resting cardiac output appears normal, patients with borderline hypertension exhibit underlying autonomic dysregulation characterized by decreased vagal inhibition and reduced responsiveness to sympathetic stimulation.
Cite This Study
Julius et al. (1975) conducted an observational in Borderline hypertension (n=230). Borderline hypertension with normal resting cardiac index vs. Control subjects was evaluated on Cardiac index and stroke volume response to autonomic blockade and isoproterenol. Borderline hypertensive patients with normal cardiac output exhibited decreased vagal inhibition and reduced cardiac responsiveness to sympathetic stimulation compared to control subjects.