Flashcards in Peripheral Vascular Disease Deck (46)
Equation for vessel flow
Q = ((P1-P2)πr^4)/8nL
Equation for vessel resistance
Proportional to nL/r^4
For stenoses of the same length and radius, what factor will cause the biggest pressure drop across the stenosis?
Flow in terms of area and velocity
A1V1 = A2V2
Graph of cardiac cycle and arterial flow
Look at lecture this seems important
High resistance arteries
Muscular arteries (arm, leg)
Mesenteric arteries (pre-prandial)
Low resistance arteries
Internal carotids, vertebrals, renals, mesenteric arteries (post-prandial)
Two factors that affect pressure in peripheral veins?
Muscular contraction and respiration.
Three characteristics of normal venous waveforms
Display respiratory phasicity
Augment with calf muscle compression
Display valvular integrity (no retrograde flow on valsalva or increased intra-thoracic pressure).
Paradigm of atherosclerosis
A systemic disease that manifests locally.
What is peripheral artery disease
Atherosclerosis of the aorta, iliac, and lower extremity arteries. Regardless of symptoms, patients with PAD have a 3x increase in CV events.
What are two factors that contribute to PAD development?
Smoking and diabetes.
Pain or fatigue in calf, thigh, buttock, or lower back that occurs with exertion and is relieved by rest. Location of symptoms corrlates with the level of obstruciton (generally one level below the disease)
Critical limb ischemia
Pain or parathesia in the lower extremity at rest. Exacerbated by leg elevation and relieved with dependency on gravity. Can have ulceration with severe ischemia
Leriche Triad of aortoiliac occlusion
Bilateral buttock/thigh claudication, impotence, and global atrophy
What are the most commonly involved arteries in PAD?
Femoral/popliteal area. Then tibeal/peroneal area, then aortoiliac area.
What area of PAD involvement is hardest to treat? Easiest?
Hardest is tibeal/peroneal. Easiest is aortoiliac.
What area of PAD is affected in DM?
5 year outcomes of PAD?
Most with stable claudication. However, many with CV related morbidity and mortality.
How to detect PAD?
Best way is the ankle/brachial index. Performed at rest and with exercise. Also leg imaging
How to conduct ankle brachial index?
Take highest ankle systolic bp (right or left) and divide by highest brachial systolic bp (right or left).
What is normal ABI? What is severe obstruction? What if ABI is greater than normal?
Normal ABI is .9-1.4. Severe obstruction is 1.4, then calcification
Normal vs obstructed arterial pulse waveforms
Normal has rapid upstroke and dicrotic notch.
Obstructed has delayed rise, rounded peak, convex decay..
Why treat PAD?
Primarily to reduce CV events, then to improve symptoms
How to treat PAD
1) stop smoking, control BP w/ace inhibitor, control lipid with statins, control platelet aggregation with aspirin/clopidogrel
2) Walking, treat with cilostazol, revascularize
Sources of acute arterial occlusion
In situ thrombosis (plaque rupture), embolism, trauma, vasculitis, severe venous thrombosis
Signs of acute limb ischemia
Painful, pulseless, paralyzed, parathesias, pallor, poikilothermia.
Symptoms lasting less than 2 weeks.
AKA buerger's disease
Segmental inflammation of medium sized arteries AND veins in 2 or more limbs. This causes thrombosis and vasospasm.
Not related to atherosclerotic disease.
What causes Thromboangitis obliterans
Tobacco is the leading precipitant and it occurs in men>women, less than 40.