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Effects of Blood Pressure, Smoking, and Their Interaction on Carotid Artery Structure and Function
Yu-Lu Liang1, Louise M. Shiel, Helena Teede
1Vascular Research Group (Y.-L.L., L.M.S., H.T., D.K., B.P.M.), Department of Medicine, and Department of Epidemiology and Preventive Medicine (J.M.), Monash University, Melbourne, Australia.
Insights
Hypertension and smoking both increase carotid artery wall thickness and stiffness. While hypertension raises arterial stress, smoking primarily affects arterial stiffness, not lumen-to-wall ratio.
Area of Science:
- Cardiovascular Medicine
- Vascular Biology
- Biomedical Engineering
Background:
- Arterial geometry and wall stress are critical determinants of cardiovascular health.
- Hypertension and smoking are major risk factors for cardiovascular disease, influencing arterial structure and function.
- Understanding their individual and interactive effects on carotid arteries is essential for risk stratification.
Purpose of the Study:
- To investigate the relationships between carotid blood pressure, arterial geometry, and wall stress.
- To determine the impact of hypertension, smoking status, and their interaction on these vascular parameters.
- To assess how carotid artery remodeling responds to these risk factors.
Main Methods:
- Cross-sectional study of 679 adults (49-82 years), including smokers and nonsmokers.
- Measurement of brachial and carotid pulse pressures, carotid intima-media thickness (IMT), lumen diameter (D), and stiffness index (SI).
- Calculation of circumferential stress using the Laplace relationship; adjustments for age, height, and heart rate.
Main Results:
- Hypertension and smoking significantly increased IMT, D, and SI, both individually and interactively.
- Hypertensive subjects showed increased radius-to-wall thickness ratio (R/IMT) and circumferential stress.
- SI correlated with IMT, while R/IMT inversely correlated with central pulse pressure; smoking did not affect these correlations.
Conclusions:
- Carotid artery remodeling follows Laplace's law but inadequately prevents increased stress in hypertension.
- Hypertension and smoking induce significant changes in carotid artery geometry and stiffness.
- Smoking impacts arterial stiffness more than lumen-to-wall ratio, unlike hypertension.
Abstract:
-In the present study, we examined the relationships among carotid blood pressure, arterial geometry, and wall stress and determined the impact of hypertension, smoking status, and their interaction on these relationships. The study involved 679 subjects aged 49 to 82 years: 372 smokers (190 men and 182 women) and 307 nonsmokers (110 men and 197 women). Blood samples were taken to determine total cholesterol levels. Central pulse pressure was derived from measured brachial artery pressure with a linear regression equation from data obtained in a subgroup of 276 subjects that related brachial and carotid pulse pressures; the latter was measured with applanation tonometry. Carotid intima-media thickness (IMT), lumen diameter (D), and stiffness index (SI) were determined with high-resolution B-mode ultrasound. Mean and pulsatile circumferential stress (final sigma(C)) was calculated according to the Laplace relationship. Indexes of arterial geometry and function were adjusted for age, height, and heart rate. Hypertension (treated and/or screening blood pressure of >140/90 mm Hg) was present in 71 nonsmokers and 186 smokers. Nonsmokers and smokers did not differ in blood pressure and cholesterol levels. Hypertension and smoking individually and interactively significantly increased adjusted IMT, D, and SI. The radius-to-wall thickness ratio (R/IMT) (where R=D/2) and final sigma(C) were increased in hypertensives. SI was correlated with IMT (r=0.56, P:<0.001); radius-to-wall thickness ratio was inversely correlated with central pulse pressure (r=-0.38, P:<0.001). Smoking did not influence these relationships. In conclusion, carotid artery wall remodeling appears to follow Laplace's law but is insufficient to prevent an increase in circumferential stress in hypertensive subjects. Unlike hypertension, smoking does not influence the lumen-to-wall ratio but has a significant effect on wall stiffness.