Flashcards in Lec 23 Peripheral Vascular Disease Deck (77)
What is equation for blood flow [poiselle]?
Q = P*pi*r^4 / 8nL
Q = P/R
What factor has greatest impact on blood flow?
radius of the vessel
For two stenoses of same length and radius, what will higher flow rate due to pressure drop across the stenosis?
higher flow --> higher pressure drop
What happens to blood flow as area reduces?
- speed of flow increases
- becomes more turbulent
What happens to flow of blood in systole? diastole?
systole: early = rapid flow of blood out then slows down
diastole: have recoil [neg flow] as heart fills up
What are some examples of high resistance arteries?
- muscular arteries to arm, leg, external common carotid [to face muscles]
- mesenteric arteries before you eat
What is difference in flow high vs low resistance vessels?
high resistance --> get flow mostly just with systole; very low flow with diastole
low resistance --> still get good flow with diastole = more essential organs
What are some examples of low resistance arteries?
- internal carotids
- vertebral arteries
- renal arteries
- mesenteric arteries after you eat
Are peripheral veins high or low resistance?
low resistance --> communicate directly with heart
hat are some characteristics of normal venous waveform?
- respiratory phasicity
- augmented with calf muscle compression
- demonstrate valve competence [no retrograde flow w/ valsalva]
How do you detect valve competence?
ask patient to valvsalva
if you pick up blood flow = incompetent valve
What is peripheral artery disease?
atherosclerosis of aorta, iliac, and lower extremity arteries
What risks associated with peripheral artery disease?
regardless of symptoms it gives you a 3x increase risk in CV events
Who is at risk for getting peripheral artery disease?
- people who smoke and have diabetes
- people with chronic kidney disease
What are clinical manifestations of peripheral artery disease?
intermittent claudication or critical limb ischemia
What is intermittent claudication?
pain or fatigue in calf/thigh/buttock or low back that occurs with exertion and relieve by rest
location of symptoms correlates with one level below disease/obstruction
What are symptoms of critical limb ischemia? what exacerbates/improves?
- pain or parasthesia in lower extremity at rest
- ischemic uclerations
- exacerbated by leg elevation [or when supine] = elevation pallor
- relieved by hanging foot over the side of bed = dependent rubor [filled w/ blood]
What is leriche triad?
classic triad of symptoms related to aortic and iliac atherosclerosis
- bilateral butt and thigh claudication
- global atrophy of extremity
What is most frequent location of peripheral artery disease?
femoro-popliteal is most common
What is prognosis of aorto-iliac peripheral artery disease? Where do you feel the pain?
collateral typically well developed --> good prognosis for revascularization with high patency
feel the pain in thigh
What is order of patency rates in revascularization procedures for peripheral artery disease of the following vessels:
patency decreases as you go down
Aorto-iliac > femoro-popliteal > tibial-peroneal
What is prognosis of femoro-popliteal peripheral artery disease? where do you feel the pain?
collateral determine course
intermediate patency rate with revascularization
What is prognosis of tibial-peroneal peripheral artery disease? where do you feel the pain?
associated with DM
low graft patency rates
How do people with PAD initial present?
- atypical leg pain
- very rare critical limb ischemia
What is 1 yr prognosis of critical limb ischemia?
50% alive w/ 2 limbs
25% CV mortality
What is 5 yr prognosis of pts with peripheral artery disease?
mostly fine at 5 yrs
20% have non-fatal CV event
What physiologic testing to detect PAD?
- ankle/brachial or toe/brachial index
- pulse volume recordings
- segmental limb pressures
- continuous wave doppler
What is purpose of ankle-brachial index? how do you calculate?
to detect pressure differences between arms and legs that tell you if there is an obstruction between the two
calculate left ABI
take highest systolic BP of L posterior tibial or L dorsalis pedis = L ankle BP
take highest brachial systolic BP between R and L [ex. if R = 160 and L = 120 use 160 for all calculations]
L ABI = L ankle BP / highest brachial BP
What is a normal ABI? obstructed?
normal = 0.9-1.4
< 0.9 = mild obstruction
0.4-0.7 = moderate obstruction
< 0.4 = severe obstruction
> 1.4 = calcified vessel