Haemodynamic concepts Flashcards
What are the signs of stenotic disease?
- Increased flow velocity immediately downstream from the affected area.
- Spectral broadening in the immediate post stenotic portion of the vessel
Define spectral broadening?
On doppler the wave form shows a wider range of doppler shifts, the doppler signal appears ‘filled in’ to the baseline on the trace. This occurs immediately post a severe stenosis where chaotic/turbulent flow is present.
What are the arterioles known as?
Resistance vessels, the size and number of arterioles contributes to the resistance.
According to Poiseuille’s law, if a diameter of a conduit is halved, flow volume reduces by a factor of:
16
The acceleration of blood in a stenosis is due to which haemodynamic principle?
Bernoulli’s principle
A straight non-branching pipe measuring 2 cm in diameter and 10 cm in length is filled with water. The pressure is 1 mmHg at one end of the pipe and 1 mmHg at the other end. Determine the volume flow rate in the pipe.
0 mL/min
______ are more compliant than arteries?
Veins are more compliant than arteries
It is evident that a small increase in volume of the vessel is associated with a rapid increase in pressure in arteries, but only a modest increase in pressure in veins. What principle accounts for this relationship?
Differences in vascular compliance
Stenosis is usually represented as percent diameter reduction of a vessel. Given a diameter reduction of 50%, what is the percentage of surface area reduction?
~75%
Between 0 and 95% stenosis, as the % diameter of stenosis increases, the flow velocity?
increases.
Beyond 95% stenosis, further reduction in vessel diameter is associated with ‘___________’ flow velocity.
Reducing
True or False: It is possible to have a normal flow velocity in a highly diseased vessel.
True
Which equation is used to estimate the pressure drop across a lesion using velocity measurements?
modified Bernoulli equation
What is laminar flow
Smooth stable flow
