Hemodynamics

of

Large

Arteries

93

. . . . .

.........

_i

..-.

...........................

..

...

...

.....

Fig.

4.2.3:

Simultaneously recorded electrocardiogram (top panel), blood pressure

(middle panel) and ascending aortic flow (bottom panel) waveforms. Pressure waveforms

in the ascending aorta (first left), descending thoracic aorta (second left), the abdominal

aorta (second right) and the iliac artery (first right) are shown.

The more distal the pressure pulse away from the heart, the larger is

its amplitude. This is attributed to the larger amplitudes of peripheral

wave reflections. Such reflections have been suggested as a closed-end

type, with the principal sites of reflections in the arterioles.

Structural

and geometric changes along a vessel also give rise to reflections, but are

of smaller magnitudes. Reflections, in general, have opposite effects on

pressure and flow.

Geometric

nonuniformities

constitutes

the

second

factor

that

influences the pulse waveforms. These may be tapering or vascular

branching. The many aspects of vascular branching is the subject of the

following chapter.

The third influential factor is elastic nonuniformity.

The vascular

wall becomes progressively stiffer toward the periphery owing to