duplex arterial scanning unit 2

reasons for noninvasive arterial testing

evaluate: arterial disease, pulsatile masses, suspected arterial trauma, angioplasty/stent placement. baseline study before surgery reconstruction, postoperative follow-up, aid in diagnosis of occlusions, supplement clinical judgement

lower extremity duplex imaging

aorta through entire limb

upper extremity duplex imaging

innominate through entire limb

limitations of lower extremity imaging

no visualization of iliacs because of bowel gas or obesity, shadowing from calcs, imaging of popliteal trifurcation/anomalies, difficulty evaluating lesions distal to stenosis because of low velocities

abnormal color findings include:

aliasing, reduced flow channel, color bruit

normal spectral analysis findings:

PSV does not increase, normal, high-resistance spectral waveform, triphasic

velocity ratios

can be used to help classify disease severity

3 major waveform changes - signs of disease

increase in PSVs >100%, spectral broadening and turbulence, loss of reversal of flow

greater than or equal to 50% stenosis

PSV velocity greater than or equal to 2

greater than or equal to 70% stenosis

PSV velocity ratio greater than or equal to 3

suggest a severe stenosis

PSV > 300 cm/s

distal to a hemodynamically significant stenosis

more low resistance flow characteristics, delayed rise to peak systole

proximal to an occlusion

very high resistance pattern, antegrade flow component only during systole, no flow during diastole

contrast arteriography

gold standard for diagnosis of arterial stenosis, can be used when duplex imaging is limited

treatments for PAD

aim to decrease patient symptoms and improve prognosis by preventing the risk of further cardiovascular events, 3 types: medical management/conservative, endovascular, surgical

management/conservative treatment for PAD

control risk factors, exercise, pharmaceutical agents

endovascular treatment for PAD

revascularize limbs, endovascular procedures: angioplasty, endografts, atherectomy, thrombin injections

surgical treatment for PAD

most common: bypass graft surgery, thrombectomy, endarterectomy

endarterectomy

cut open the vessel and clean it out

angioplasty

uses a balloon-tipped catheter to open a blocked blood vessel and improve blood flow

atherectomy

a procedure that utilizes a catheter with a sharp blade on the end to remove plaque from a blood vessel

stent

a tiny expandable mesh tube that can be inserted into a blocked passageway to keep it open

prosthetic (synthetic) bypass graft

made of various manufactured materials (PTFE, dacron), associated with poor long-term patency rates

autogenous vein

preferred graft material, better long-term patency rates, must be carefully monitored in short term for early complications and failure

autogenous: in situ bypass graft

vein being used for bypass is left in its original anatomic position - usually the great saphenous vein, branches must be ligated, valves must be lyzed to allow blood flow downward, large end of vein anastomosed to large end of artery; small end of vein anastomosed with small end of artery (better size match)

autogenous: orthograde

involves lyzing valves

autogenous: retrograde

involves “flipping” the vein; valves do not need to be removed, large end of vein now anastomosed to small end of artery

bypass graft failure within 30 days

retained valve or valve leaflet, intimal flap, suture defect, graft entrapment due to improper positioning, thrombosis

bypass graft failure between 1 and 24 months

Myointimal hyperplasia can develop creating stenosis, stenosis at proximal or distal anastomosis - most common cause of graft revision in this postoperative period

bypass graft failure after 24 months

progression of atherosclerotic disease in inflow or outflow vessels, aneurysmal dilation (conduit or anastomotic site - where they connect)

retained valves

valve or valve remnants that remain due to incomplete valve disruption during surgery, large remnants or valve leaflets can produce flow-limiting stenosis, appears as bright echoes within graft lumen

myointimal hyperplasia

rapid proliferation of cells into intimal layer, can occur any point along bypass conduit, typically occurs in areas where vein has sustained injury or valve sinus, can result in stenosis

normal velocities in bypass graft

typically below 150 cm/s

abnormal velocities in bypass graft

PSV > 180 cm/s

greater than or equal to 50% stenosis in bypass graft

PSV velocity ratio of 2, PSV 180-300 cm/s

greater than or equal to 75% stenosis in bypass graft

PSV ratio of 3.5 and PSV > 300 cm/s

peripheral arterial aneurysms

most commonly present in the popliteal artery, most common cause for pseudo - puncture or trauma to the wall, not likely to rupture, can be limb threatening due to distal embolization which occurs in approx. 35% of cases left untreated

pseudoaneurysm

perivascular collection that communicated with artery or graft and has presence of pulsating blood entering collection, track neck of variable length connects native vessel to collection, can be unilocular or multilocular

treatment for pseudoaneurysms

compression therapy, US-guided thrombin injection, surgery