Related Experiment Videos
Hemodynamics of the carotid artery after vasodilation in essential hypertension
S Laurent1, P Lacolley, G London
1Diagnosis Center, Broussais Hospital, Paris, France.
Insights
Hypertension alters carotid artery hemodynamics, causing decreased blood flow and increased resistance, unlike the brachial artery. These changes may affect baroreceptor reflex function in hypertensive individuals.
Area of Science:
- Cardiovascular Physiology
- Hypertension Research
- Arterial Wall Mechanics
Background:
- Sustained essential hypertension is characterized by elevated blood pressure.
- The differential response of large arteries to chronic hypertension is not fully understood.
- Carotid artery hemodynamics and baroreceptor reflex function are critical in blood pressure regulation.
Purpose of the Study:
- To compare hemodynamics and arterial caliber of the common carotid artery (CCA) and brachial artery in hypertensive vs. normotensive subjects.
- To investigate the influence of CCA circulation on baroreceptor reflex response to vasodilation.
- To explore potential intrinsic alterations in the arterial wall of the CCA in hypertension.
Main Methods:
- Simultaneous noninvasive measurements of CCA and brachial artery hemodynamics.
- Assessment of arterial diameter and blood flow at equivalent mean arterial pressures.
- Hemodynamic measurements before and after cadralazine administration in normotensive and hypertensive subjects.
Main Results:
- Hypertensive subjects showed normal brachial artery blood flow but reduced CCA blood flow and increased CCA resistance.
- CCA diameter was normal in hypertensive subjects, while brachial artery diameter was increased.
- Cadralazine decreased CCA tangential tension in hypertensive subjects, correlating with heart rate increase, suggesting altered baroreceptor reflex resetting.
Conclusions:
- The CCA exhibits distinct hemodynamic and structural adaptations to chronic hypertension compared to the brachial artery.
- Intrinsic alterations in the CCA arterial wall may contribute to baroreceptor reflex resetting in hypertension.
- CCA circulation plays a role in modulating baroreceptor mechanisms during drug-induced vasodilation in hypertensive patients.
Abstract:
We performed simultaneous noninvasive measurements of common carotid artery and brachial artery hemodynamics in nine normal subjects and 10 subjects with sustained essential hypertension. In hypertensive subjects, brachial artery blood flow and forearm vascular resistance were in the normal range while carotid artery blood flow and carotid artery resistance were decreased and increased, respectively. The most important findings were the changes in the internal caliber of large arteries. Although the brachial and carotid artery diameters of hypertensive subjects were measured for the same level of mean arterial pressure, brachial artery diameter was significantly increased and carotid artery diameter was strictly normal as compared with values found in normal subjects. To assess whether carotid artery circulation could influence the baroreceptor reflex response to arteriolar vasodilation, carotid artery and brachial artery hemodynamics were measured in immediate succession in normotensive and hypertensive subjects before and after oral administration of cadralazine, a dihydralazine derivative. After cadralazine treatment, carotid artery tangential tension decreased in hypertensive subjects, and the changes were significantly correlated to the increase in heart rate. A similar correlation was found in normal subjects, but it was reset toward higher heart rates. These results indicate that the carotid artery does not behave like the brachial artery in response to a chronic increase in blood pressure. This behavior indicates intrinsic alterations of the arterial wall and might be involved in the resetting of the carotid baroreceptor reflex. Carotid artery circulation could play a role in hypertension by modulating the carotid baroreceptor mechanisms involved in the response to drug-induced arteriolar vasodilation.(ABSTRACT TRUNCATED AT 250 WORDS)