Poiseuille’s Law
What factor determines flow speed the most in arteries?
Radius of the vessel
Based on Bernoulli principle. Velocity and pressure increase together. (True or False)
False
Arteries have thicker walls then veins. (True or False)
True
Veins send blood away from the heart (True or false)
False (Reasoning: Veins usually send blood towards the heart to become oxygenated again)
You're scanning a 67 YOM with a hx of HTN, PAD, and smoking (current 2ppd). This is a follow up LEA exam to monitor a known stenosis. When you get to their popliteal artery, you notice turbulent waveforms followed by monophasic flow throughout their calf. Where might there be a stenosis? (distal SFA, peroneal artery, distal popliteal artery)
distal SFA. After a significant stenosis upstream, Turbulence happens as a form of non-laminar flow due to the disturbance of flow causing the stenosis.
What power is radius raised by?
4th power
At the maximum velocity of a stenosis, what happens to the pressure?
Pressure decreases
What are the three layers of arteries?
Tunica adventitia, Tunica media, Tunica intima.
What is the longest vein in the body?
GSV (Great/large saphenous vein)
You're doing a follow up carotid exam on a 73 YOM. This is a follow up exam to access progression of disease. As you're scanning, you notice that the proximal ICA is aliasing even through your color PRF is in the appropriate range. What is causing the aliasing effect?
Nyquist limit due to high flow speeds
If there is an increase in blood viscosity, what happens to resistence?
Resistance increases (R∝η) Resistance is proportional to viscosity.
What is resistance controlled by for arteries?
Arterioles
Which veins send oxygenated blood back towards the heart?
Pulmonary veins
72 YOF. Hx of HTN, smoking. The pt has no priors but mentions dizziness and unilateral weakness of the left arm. As you're scanning the left side of their neck, you notice retrograde flow of their vertebral artery. After the exam, you take their BP and notice the left arm mmHg is lower than the right. What might be casing this?
Evidence of a Stenosis vs occlusion of the left subclavian artery
If the length of a vessel doubles while everything else remains the same, what happens to resistance?
Resistance doubles. Length and resistance are proportional.
What layer of an artery is affected when there is a dissection within the vessel?
Tunica intima (Reasoning: a dissection affects the innermost layer of a vessel. Connective tissue tears and separates created a false lumen. This lumen can affects the hemodynamics of a vessel and can lead to a stenosis, retrograde, or an occlusion.
What pump in the calf sends blood back towards the heart?
Calf muscle pump
You're scanning a carotid and get to the ICA and ECA bifurcation. Based on how resistance works for these vessels (ICA needs more consistent blood flow compared to the ECA), what resistance should be found in the ICA and ECA?
ICA: Low resistance
ECA: High resistance
Vessel A. Vessel A is 1/16, while vessel B is 1/256. The bigger the radius, the less resistive it is. So based on Poiseuille's law, Vessel A will have more resistance.
What is a fistula, and what two vessels are commonly used for one?
A connection between a vein and an artery. (Brachiocephalic or radiocephalic AV fistula)
When a vein is dilated. Is transmural pressure large or small?
Large. Since there is a increase in blood, the pressure inside the vein compared to the surrounding tissue is increased.
101 YOF. Hx of DVT, venous insufficiency. Pt had complaints of bilateral leg swelling and pain. The patient used to be on compression stockings but currently is not on them. As you're scanning their GSV you notice reflux throughout the thigh, knee, and calf. What is most likely causing their venous insufficiency?
Valve incompetence. (Transmural pressure in the legs increase due to the valves not holding the blood. This causes blood to flow backwards and pool in the legs. And since blood flows high pressure to low pressure, perforators in the deep system cause blood to flow into the GSV and cause swelling/ varicose veins)