Thu18November0253AM 1

Systemic vascular resistance is often used a measure of left ventricular afterload.

Which one of the following options has most influence on systemic vascular resistance?

(Please select 1 option)

Haematocrit

Small arterioles Correct

Pre-capillary arterioles

Blood temperature

Capillaries

Explanation

The most important factor that determines the systemic vascular resistance (SVR) is the tone of the small arterioles.

These are otherwise known as resistance arterioles. Their diameter ranges between 100 and 450 µm. Smaller resistance vessels, less than 100 µm in diameter (pre-capillary arterioles), play a less significant role in determining SVR. They are subject to autoregulation.

Any change in the viscosity of blood and therefore flow (such as due to a change in haematocrit) might also have a small effect on the measured vascular resistance.

Changes of blood temperature can also affect blood rheology and therefore flow through resistance vessels.

Systemic vascular resistance (SVR) is measured in dynes·s·cm-5

It can be calculated from the following equation:

SVR = (mean arterial pressure - mean right atrial pressure) × 80

cardiac output

Answer Statistics

1

3%

2

38%

3

49%

4

5%

5

7%

Times answered: 249