Influence of arterial pulse and reflected waves on blood pressure and cardiac function☆,☆☆,★

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Abstract

An integrated view of the role of arterial blood pressure in cardiovascular physiology should consider both the steady (mean blood pressure) and pulsatile (systolic, diastolic, and pulse pressures) components. This brief overview describes the important factors influencing these components, with emphasis on the consequences of arterial stiffening. In addition to their conduit function, arteries also perform a cushioning function that transforms the pulsatile flow generated by contraction of the left ventricle into steady flow at the periphery. Arterial compliance is a principal determinant of arterial blood pressure and is both pressure dependent and affected by vascular biomechanics. Other important factors that affect the steady and pulsatile components of blood pressure include ventricle performance, peripheral resistance, pulse wave velocity, and the timing of pulse wave reflections. Ageing and hypertension are important factors that contribute to reductions in arterial compliance. Important functional effects of this are that both the amplitude of the arterial pulse wave and pulse wave velocity increase, causing an early return of reflected waves from the periphery to the aorta. This may boost aortic and left ventricular pressures during systole at the expense of diastolic pressure, which is reduced. Studies have shown that stiffening of arteries and the associated increase in systolic and pulse pressures are important cardiovascular risk factors. Patients with an increased risk of cardiovascular events associated with such changes should be identified and receive appropriate therapeutic interventions. (Am Heart J 1999;138:S220-S224.)

Section snippets

Conduit function of arteries

To perform the conduit function effectively, large arteries need to deliver the amount of blood from the heart to the peripheral tissues, dictated by metabolic activity. To ensure efficient metabolic exchange, a continuous, steady, and effectively constant flow of blood is required in the arteriolar and capillary systems. To maintain such a steady flow, a constant pressure head (represented by mean blood pressure) must be applied to overcome resistance to flow caused by blood viscosity and

Cushioning effect of arteries

The principal role of arteries as cushions is to dampen the pressure oscillations that are caused by the intermittent nature of ventricular ejection.2 The efficiency of this cushioning function is determined by the viscoelastic properties of arterial walls described in terms of compliance, distensibility, or stiffness (the inverse of distensibility). Compliance is assessed by the relation between changes in distending pressure (ΔP) inside the artery and concomitant changes in radius (or in

Timing of reflected waves

The mechanical properties of arterial walls are also determinants of the propagation and reflection of pressure waves along the arteries. Ventricular ejection generates a primary (or incident) pressure wave that moves away from the heart at a finite speed, termed pulse wave velocity, which increases with arterial stiffening. The incident wave is reflected at any point of structural or geometric discontinuity of the arterial tree, generating a reflected wave traveling backward toward the

Factors increasing arterial stiffness

Ageing and hypertension are the most common factors leading to arterial stiffness, whereas genetic or environmental factors may increase arterial stiffening and accelerate the effects of age and hypertension. In terms of vascular mechanics, it is generally accepted that the composition of blood vessels influences the distensibility of the vessel wall.4, 5 In human beings, with ageing and hypertension, the arteries stiffen as the result of progressive degeneration of arterial media with

Clinical relevance of decreased arterial distensibility

As already described, an important functional effect of the stiffening produced by such arterial damage is that the amplitude of component waves and pulse wave velocity increase, causing an early return of reflected waves from the periphery to the aorta, boosting aortic and left ventricular pressures during systole at the expense of mean diastolic pressure, which is decreased. The most obvious consequences of these alterations are mismatch between aortic ventricular afterload and left

Summary

As discussed, arterial pulse and reflected waves have a significant impact on blood pressure and ultimately, therefore, on cardiac function. A principal determinant of both steady and pulsatile arterial blood pressure components is arterial compliance. Arterial stiffening, caused primarily by ageing and hypertension, increases the amplitude of the arterial pulse wave and pulse wave velocity, causing early return of reflected waves to the aorta. This, in turn, results in an associated increase

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