Vascular Hemodynamics Principles Flashcards

Which hemodynamic principle explains why blood velocity increases when a vessel narrows?

Answer: Continuity of flow equation

The continuity equation states that flow volume is conserved, so velocity must increase when cross-sectional area decreases.

In a stenotic vessel, the pressure gradient across the lesion is primarily determined by:

Answer: Flow velocity and lesion geometry

The pressure gradient across a stenosis depends on flow velocity squared and the geometric characteristics of the narrowing.

The ankle-brachial index (ABI) in a normal individual should be approximately:

Answer: 0.9–1.3

A normal ABI ranges from 0.9 to 1.3; values below 0.9 suggest peripheral arterial disease.

Which waveform characteristic indicates high distal vascular resistance in a peripheral artery?

Answer: Triphasic waveform with prominent reverse component

A triphasic waveform with a prominent reverse-flow component in early diastole is the hallmark of high distal resistance.

What does a markedly elevated pulsatility index (PI) in a renal artery most likely indicate?

Answer: Elevated renal vascular resistance

An elevated PI in the renal artery reflects increased downstream vascular resistance, often seen in chronic renal disease.

Which parameter best distinguishes a hemodynamically significant carotid stenosis from a non-significant one on Doppler?

Answer: Peak systolic velocity in the ICA

Peak systolic velocity in the internal carotid artery is the primary Doppler criterion for grading stenosis severity.

Turbulent flow in a blood vessel is most likely to occur when the Reynolds number exceeds:

Answer: 2000

Reynolds numbers above approximately 2000 are associated with the transition from laminar to turbulent flow.