In vivo determinants of arterial stiffness

Pulse pressure--a review of mechanisms and clinical relevance

The goal of this study was to review the origin, clinical relevance and treatment of pulse pressure (PP). Elevated PP is increasingly being recognized as a risk factor for cardiovascular, particularly coronary, disease. Pulse pressure is discussed in terms of both Windkessel and distributive models of the arterial circulation. Pulse pressure arises from the interaction of cardiac ejection (stroke volume) and the properties of the arterial circulation. An increased stiffness of the aorta and large arteries leads to an increase in PP through a reduction in arterial compliance and effects on wave reflection. A number of factors are known to influence arterial wall behavior and, therefore, PP. In addition to the effects of aging and blood pressure on arterial wall elasticity, there is some evidence that atherosclerosis, per se, amplifies these effects. Thus, the relationship between PP and coronary disease may be bidirectional. A number of dietary and lifestyle interventions have been shown to modify large artery behavior. These include aerobic exercise training and consumption of n-3 fatty acids. Conversely, strength training is associated with an increase in arterial stiffness and a higher PP. The effects of antihypertensive medication have been extensively studied, but many studies are difficult to interpret because of concomitant change in blood pressure, and to a lesser degree, heart rate. However a number of studies do suggest direct arterial wall effects, particularly for angiotensin-converting enzyme inhibitors. A distributed compliance model of the arterial circulation provides a framework for understanding the causes, effects and potential treatment of elevations in PP.

Hormonal therapy increases arterial compliance in postmenopausal women

OBJECTIVES

This study investigated the effects of hormonal therapy on large arterial properties.

BACKGROUND

Arterial stiffness is an emerging risk marker for coronary heart disease and is potentially modifiable. Postmenopausal use of hormonal therapy is associated with a lower risk of coronary heart disease.

METHODS

Total systemic arterial compliance (SAC) and pulse wave velocity (PWV) were determined in 26 premenopausal and 52 postmenopausal women, 26 of whom were taking hormonal therapy.

RESULTS

Arterial compliance was greater in the premenopausal group (mean +/- SEM 0.57 +/- 0.04 arbitrary compliance units [ACU]) than in the postmenopausal group not taking hormonal therapy (0.26 +/- 0.02 ACU, p = 0.001). Postmenopausal women taking hormonal therapy had a significantly increased total SAC compared with women not taking hormonal therapy (0.43 +/- 0.02 vs. 0.26 +/- 0.02 ACU, p = 0.001). PWV in the aortofemoral region in the premenopausal women was 6.0 +/- 0.2 vs. 8.9 +/- 0.3 m/s (p < 0.001) in untreated postmenopausal women. However, postmenopausal women taking hormonal therapy had a significantly lower PWV than those not taking hormonal therapy (7.9 +/- 0.2 vs. 8.9 +/- 0.3 m/s, p = 0.01). Eleven postmenopausal women had their hormone replacement therapy withdrawn for 4 weeks, resulting in a significant decrease in SAC and a significant increase in aortofemoral PWV.

CONCLUSIONS

The increased SAC and decreased PWV in women receiving hormonal therapy suggest that such therapy may decrease stiffness of the aorta and large arteries in postmenopausal women, with potential benefit for age-related cardiovascular disorders. The reduction of arterial compliance with age appears to be altered with hormonal therapy.