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Elastic properties and Windkessel function of the human aorta
1Zentrum für Kardiovaskuläre Pharmakologie, Mainz-Wiesbaden, Germany.
Insights
Aortic elastic properties, crucial for cardiovascular function, act as a Windkessel to ensure continuous blood flow. Increased aortic stiffness, linked to aging and disease, negatively impacts blood pressure and heart function.
Area of Science:
- Cardiovascular Physiology
- Biomedical Engineering
Background:
- The aorta functions as a Windkessel, storing and releasing stroke volume to maintain continuous peripheral blood flow.
- This Windkessel function reduces cardiac afterload, improves coronary blood flow, and aids ventricular relaxation.
Purpose of the Study:
- To elucidate the significance of aortic elastic properties in cardiovascular function.
- To explore the impact of aging, hypertension, and atherosclerosis on aortic stiffness.
- To review methods for assessing aortic elastic properties in vivo.
Main Methods:
- Pulse wave velocity measurement along the aorta.
- Assessment of the ratio between pulse pressure and aortic volume changes (ΔP/ΔV).
- Noninvasive ultrasonic or tomographic methods for assessing aortic volume changes.
Main Results:
- Increased aortic stiffness correlates with aging, elevated blood pressure, and atherosclerosis.
- Aortic stiffness adversely affects blood pressure (increased systolic, decreased diastolic), ventricular afterload, and diastolic subendocardial supply.
- Higher pulse wave velocity indicates greater aortic stiffness.
Conclusions:
- Aortic elastic properties are vital for cardiovascular homeostasis.
- Increased aortic stiffness is a significant pathophysiological factor, particularly in systolic hypertension.
- Accurate assessment of aortic stiffness requires consideration of blood pressure effects or correction for intrinsic wall properties.
Abstract:
An understanding of the role of the aortic elastic properties indicates their relevance at several sites of cardiovascular function. Acting as an elastic buffering chamber behind the heart (the Windkessel function), the aorta and some of the proximal large vessels store about 50% of the left ventricular stroke volume during systole. In diastole, the elastic forces of the aortic wall forward this 50% of the volume to the peripheral circulation, thus creating a nearly continuous peripheral blood flow. This systolic-diastolic interplay represents the Windkessel function, which has an influence not only on the peripheral circulation but also on the heart, resulting in a reduction of left ventricular afterload and improvement in coronary blood flow and left ventricular relaxation. The elastic resistance (or stiffness), which the aorta sets against its systolic distention, increases with aging, with an increase in blood pressure, and with pathological changes such as atherosclerosis. This increased stiffness leads to an increase in systolic blood pressure and a decrease in diastolic blood pressure at any given mean pressure, an increase in systolic blood velocity, an increase in left ventricular afterload, and a decrease in subendocardial blood supply during diastole, and must be considered a major pathophysiological factor, for example, in systolic hypertension. The elastic properties of the aortic Windkessel can be assessed in vivo in humans in several ways, most easily by measuring the pulse wave velocity along the aorta. The higher this velocity, the higher the elastic resistance, that is, the stiffness. Other methods depend on assessment of the ratio between pulse pressure and aortic volume changes (delata P/delta V), which can be assessed noninvasively by ultrasonic or tomographic methods. All assessments of vessel stiffness have to take into account the direct effect of current blood pressure, and thus judgements about influences of interventions rely on an unchanged blood pressure. Alternatively, to derive the "intrinsic" stiffness of the aortic wall one has to correct for the effect of the blood pressure present. Recently reports about pharmacologic influences on the elastic properties of the aorta have emerged in the literature.(ABSTRACT TRUNCATED AT 400 WORDS)