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Evidences supporting an increased sympathetic tone and reactivity in a subgroup of patients with essential
Insights
Elevated circulating catecholamines (CA), particularly norepinephrine (NE), indicate heightened sympatho-adrenal activity in hypertension. Hyperadrenergic patients showed increased cardiac function and responded better to beta-blockers.
Area of Science:
- Cardiology
- Endocrinology
- Hypertension Research
Background:
- Circulating catecholamines (CA) serve as indicators of sympatho-adrenal activity.
- Hypertension studies reveal elevated CA levels in a significant portion of patients with labile and stable forms.
Purpose of the Study:
- To investigate the role of sympatho-adrenal activity in hypertension.
- To differentiate hypertensive subgroups based on CA levels and assess their characteristics and treatment response.
Main Methods:
- Measurement of resting and positional changes in circulating catecholamines (norepinephrine and epinephrine).
- Assessment of heart rate and myocardial contractility.
- Evaluation of patient response to beta-blocker therapy (propranolol, metoprolol).
Main Results:
- About 50% of labile and 30% of stable hypertensive patients exhibited elevated resting CA levels.
- Hyperadrenergic subgroups showed increased CA/NE response to postural changes, faster heart rate, and enhanced myocardial contractility.
- Hyperadrenergic patients demonstrated greater responsiveness to beta-blocker treatment compared to normoadrenergic patients.
Conclusions:
- An increased sympathetic tone and reactivity are associated with hyperkinetic cardiac function in a subset of hypertensive patients.
- Circulating CA levels can identify hyperadrenergic hypertensive patients who may benefit more from beta-blocker therapy.
- Findings support the sympathetic system's role in maintaining elevated blood pressure and suggest a targeted therapeutic approach.
Abstract:
Several experimental evidences have shown that, under standarized conditions, circulating catecholamines (CA) or norepinephrine (NE) levels can be used as a valid index of the sympatho-adrenal activity in animal and man. This approach in the study of hypertensive patients has permitted to uncover that about 50% of patients with labile hypertension and about 30% of patients with stable hypertension had elevated CA levels at rest for 20 minutes in the supine position. The increased CA levels were mainly due to a rise in NE in stable hypertension and to a rise in epinephrine (E) in labile hypertension. On the basis of circulating CA levels, the hypertensive patients were divided into hyperadrenergic (CA levels above normal range) and normoadrenergic (CA levels within the normal range) subgroups. The hyperadrenergic labile or stable hypertensive subgroups were found to be also characterized by an enhanced CA or NE increase in response to change in position from supine to standing, by a faster heart rate and by an increased myocardial contractility, while these parameters were normal in the normoadrenergic subgroups. These findings support therefore the existence of an increased sympathetic tone and reactivity in association with hyperkinetic cardiac functions in an important population of hypertensive patients. In response to two weeks treatment with beta-blockers (either propranolol or metoprolol) hyperadrenergic stable hypertensive patients were found to be more responsive to this therapy than normoadrenergic patients although both groups had the same initial blood pressure. Moreover, this treatment lowered basal NE or CA levels and restored the enhanced CA or NE response to change in position toward normal in hyperadrenergic patients while it did not modify significantly circulating supine or standing CA and NE in normoadrenergic patients. These findings strongly support a participation of the sympathetic system in the maintenance of an elevated blood pressure in hyperadrenergic patients and raise the possibility of using a more rational approach in the therapy of hypertension.