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
What happens if ankle-brachial index > 1.4
means the vessel is calcified so its not really a valid reading
need to do the toe brachial instead
How do you calculate toe-brachial index? normal value?
great toe pressure / brachial pressure
normal > 0.7
When do you use toe-brachial index instead of ankle-brachial index?
in setting of vessel non-compressibility [BP > 250 mmHg] or ABI > 1.4
b/c smaller vessels are not affected by calcification
What is association ankle-brachila index and mortality?
pts with low ABI = much higher mortality than normal
pts with > 1.4 have slightly higher mortality than normal
How do you measure arterial pulse volume recordings?
leave BP cuff inflated
measure volume displacement of blood in each wave form
What is use of segmental BP?
identify location of disease [>20 mmHg drop]
What is duplex US?
non invasive imaging for elavaluating hemodynamics and detect stenosis > 50%
What is use of MR angiography in peripheral artery disease?
may over estimate degree of stenosis
limited in setting of metal, intravascular stents/coils
When can you not use MR and CT angiography?
limited in renal failure
Does MR angiography under or over estimate degree of stenosis?
What is limitation of CT angiography in peripheral artery disease?
limited in evaluation of calcified vessels
What are goals of peripheral artery disease treatment?
decrease cardiac events/death
What are measures to decrease cardiac events and death in PAD?
- stop smoking
- control BP: ACE inhibitor
- control lipids: statins
- antiplatelets: aspirin/clopidogrel
- regular exercise
- control diabetes
What medications do you give in peripheral vascular disease?
- ACE inhibitor to control BP
- statins to control lipids
- aspirin/clopidogrel = decrease risk clots
- cilostazol = improve symtpoms
What are measures do increase function/symptoms in PAD?
walking program = walk to point of pain repeatedly --> develop collateral circulation and build up tolerance
drugs: cilostazol = decreases symptoms; mech unknown
revascularization if doesn't respond to med therapy
What are 2 major causes of acute arterial occlusion?
- in situ thrombosis --> atherosclerotic plaque rupture
- embolism from heart or aorta
What care the 6 causes of acute arterial occlusion?
- in situ thrombosis
- arterial trauma
- hypercoagulable state
- severe venous thrombosis [phlegmasia cerulea dolans]
What are the 6 P symptoms of acute limb ischemia?
- parasthesia = tingling
- poikilothermia = can't maintain body temp
What time frame for acute limb ischemia?
symptoms for less than 2 weeks
What is class I limb ischemia? treatment?
class I = no rest pain
not immediately treated
What is class II limb ischemia? treatment?
class II = ischemic rest pain, ankle pressure < 50 mmHg
mild-moderate sensory and motor deficits
treat: salvagable limb --> promptly revascularize
What is class III limb ischemia? treatment?
class III = absent doppler signals, paralysis, muscle rigor
treat: not viable limb --> amputation needed
What is buerger's diease? who gets it?
segmental inflammation of medium sized arteries and veins; involves distal vessels of upper and lower extremities. eading to thrombosis and vaospasm
men > women
age < 40 yrs
TOBACCO = cause/necessary for progression of disease
What are signs of buerger's disease? how do you differentiate from other causes?
- superficial thrombophlebitis
- raynaud's [vasospasm]
- distal arterial occlusion --> claudication
corkscrew collaterals; alternating areas of stenosis/occlusion with normal arterial segments; lack of atherosclerosis in proximal vessels; 2 or more extremities involved
rule out others by: negative test for autoimmune markers; exclude atherosclerotic embolus as cause
What is treatment for buerger's diease?
stop smoking + amputation
What should you think if you see corkscrew collaterals?
What is raynaud's phenomenon?
vasospasm of digital arteries
triphasic color response
- fingers/toes blanch to white = ischemia
- cyanosis = blue
- blood flow resumes = rubor/red
colors may be accompanies by numbness, parasthesias, or pain of affected digits
brought on by cold exposure, emotional stress
How do you diagnose primary raynauds? who gets it?
- bilateral, present at least 2 yrs without secondary cause
- onset 15-40 yrs [younger than secondary]
- women > men
- some spontaneously improve, others progress
What are symptoms of venous thrombosis?
What are varicose veins?
dilated tortuous superficial veins often in lower extremities; most common in saphenous veins
family history, women > men
due to intrinsic weakness of vessel wall from increased intraluminal pressure
What is difference primary vs secondary varicose veins?
primary = originate in superficial system; associated with pregnancy, standing, obestity
seoncdary = abnormality in deep venous system is the cause; associated with deep venous insufficiency/occlsion
Where does DVT usually occur?
calves in popliteal or higher
Where does superficial thrombophlebitis usually occur?
What is virchows triad?
puts you at risk of increased blood clot:
1 stasis of blood
2 endothelial injury
3 hypercoagulable state
What is phlegmasia cerulea dolans?
most severe form of deep vein thrombosis --> limb gets blood in but can't come out
get compartment syndrome with increasing fluid
blue painful leg --> venous gangrene
massive red/purple swelling, diminished pulses
limb and life threatening emergency!
What are some signs of DVT on ultrasound?
- dilated non-compressible veins with incomplete filling
- lack of respiratory phasicity and flow augmentation
What are the 2 major consequences of DVT?
- pulmonary emobolism
- postphlebetic syndrome
Is DVT more common in proximal vs distal veins? which are more likely to cause PE?
- distal veins more likely to develop DVT
- proximal veins at more risk of PE
proximal = iliac, femoral, popliteal
distal = deep muscular veins
What is postphlebitic syndrome?
postphlebitic syndrome = chronic venous insufficiency
- damaged venous valves / persistent occlusion by DVT --> leads to chronic leg swelling, stasis pigementation, skin ulceration
blood and fluid backflows into periphery with valsalva [increased intra-thoracic P] or even at rest = get reversal of flow; less venous return to heart
What are symptoms of pulmonary embolism?
SOB, chest pain, hemoptysis, tachycardia, hypoxia
What happens in massive PE?
have RV strain with hemodynamic compromise
--> syncope, cardiac arrest, resp failure, cor pulmonale
What happens in submassive PE?
have RV strain with hemodynamic stability and normal BP
What is chronic thromboembolic pulm HTN?
if get repeated pulm emboli over time get HTN
What are symtpoms of chronic venous insufficency?
swelling, pain, skin flaking, ulceration, varicose veins
inverted champagne bottle inflammation and fibrosis of lower 2/3 of leg
What is stasis cellulitis?
often mistaken for infectious cellultiis
does not respond to antibiotics
= warm, red tender swollen leg; inflammatory process related to venous stasis and excess interstitial fluid
treat with compression
What are 3 causes of swollen limb?
- chronic venous insufficiency
What is lipedema?
- dispropotionate fat deposition in lower half of body but torso relateively normal
- spares foot = ankle cut off sign
- bilateral and symmetric; non pitting; tender; soft
- "fat pad sign" anterior to lateral malleoli