Arterial Hemodynamics Refresher

Intima

• inner most layer

• consists offer of endothelial cells supported by an internal elastic lamina

Media

• middle layer

• consists primarily of smooth muscle cells

• allows rhythmic changes in the arterial size that occurs during cardiac cycle

• collagen is also found in this area of the wall structure

• the external elastic membrane lies between the media and the adventitia

Adventtia

• outer llayer

• contains connective tissue and collage

• contains the vasa vasorum; tiny blood vessels that supply the artery wall

The highest pressure in the arterial system is in the…ventricle and…during systole

left, thoracic aorta

The intraarterial pressure in the distal vascular bed is…during left ventricular contraction, so blood flows…the vascualr beds

lower, towards

Describe normal arterial flow:

1. In systole, intra-arterial pressure is high, flow. moves forward.

2. In diastole intra-arterial pressure is decreased and pressure distally is high (due to peripheral resistance); pressure gradient (&flow) reverses.

3. The third component is through to be due to the elasticity of the arterial wall (rebounding).

Resistive index AKA?

Pourcelot’s index

RI = (PSV - EDV) / PSV

Pulsatility index

PI =3.142 (PSV - EDV) / TAV (time avg velocity)

Why are RIs and PIs important?

increased or decreased resistance in flow reveals the presence of pathology

Changes in arterial hemodynamics are clues in diagnosing…

peripheral arterial disease PAD

Describe the hemodynamics in PAD…

1. increased resistance

2. stenosis = highest PSV

3. Post-stenotic turbulent bidirectional flow

4. Tardus parvus distal to stenosis

Changes in artery wall for inflammation and plaque are:

• monocyte migration through endothelium

• foam cells

• migration of smooth muscle cells

changes in artery wall for advanced atherosclerosis:

• fibromuscular cap (ruptured)

• blood, fibrin, platelets are released when cap ruptures

• calcium carbonate

• cholesterol crystals

• ruptured vaso vasorum

describe chronic PAD:

appears echogenic chunks of plaque, less likely to break away

describe soft plaque:

appears hypoechoic, fresh, more likely to break away