Vascular Flashcards
USF of carotid stenosis
Predominantly internal carotid artery (ICA) origin • Size: Stratification of obstruction: < 50%; ~ 50-69%; ~ 70°;6 stenosis; near occlusion; occlusion • Color Doppler: Useful for guiding angle correction during velocity measurement • Power Doppler: Useful for detecting low velocity flow at and distal to pre-occlusive stenoses • Spectral Doppler: Useful for estimating degree of stenosis with velocity parameters • <50% ICAstenosis: PSV< 125 cm/s (EDV< 40 cm/s; SVR< 2.0) • 50-69% ICAstenosis: PSV125-229 cm/s (EDV 40-99 cm/s; SVR2-3.9) • ~ 70% diameter ICA stenosis: PSV~ 230 cm/s (EDV ~ 100 cm/s; SVR~ 4.0)
Near-occlusion: Variable velocity • Occlusion: Absent flow on color/spectral Doppler • CCA stenosis: No defined Doppler criteria but ICA criteria seem to work • DSA:Gold standard for documentation of carotid stenosis/occlusion • DSAmay undercall degree of stenosis due to underestimation of outer luminal diameter at stenosis with post-bulbar diameter
Checklist for carotid stenosis
Always correlate grayscale, color Doppler, and spectral Doppler findings when evaluating carotid stenosis
USF of aortic aneurysm
Grayscale ultrasound: Bulbous or fusiform dilatation of the aorta/artery • Concentric layers of thrombus may line the interior of large aneurysms which may act as a source for distal emboli • Membrane or intimal flap may be present in dissection • Retroperitoneal hematoma is highly suggestive of aortic rupture • Hematoma is hypoechoic and asymmetrical and typically displaces ipsilateral kidney
Color Doppler: Should be incorporated in all studies of abdominal aorta • Confirm patency of celiac axis, superior mesenteric artery, renal arteries • Look for flow disturbances associated with stenosis • Measure distance between SMAand neck of aneurysm; renal arteries should be unaffected if the aneurysm begins> 2 cm inferior to the SMA • Ultrasound is an excellent non invasive tool for aneurysm screening, follow-up and useful for assessment of endoleak post endovascular repair • CTremains the gold standard and preferred imaging modality • Examine aorta from diaphragm to bifurcation • Interrogate iliac arteries
Checklist for aortic aneurysm
Measure aortic/iliac aneurysm diameter from outer wall to outer wall • Interobserver variability for aortic diameter measurement on ultrasound- 5 mm and thus significant increase in aortic diameter should only be reported when increase> 5 mm • Renal arteries should be unaffected if the aneurysm begins> 2 cm inferior to the SMA
USF of DVT
Acute thrombosis (- 14 days) • Low echogenicity thrombus: May be virtually anechoic, flow may be seen within recanalized thrombus • Venous distension: Recently thrombosed veins are distended and substantially larger than accompanying artery • Loss of compressibility: Thrombus is excluded if vein can be completely compressed • Free floating thrombus: Most recently formed clot (usually on the end closer to the heart) may not adhere to the vein wall • Collateralization: Tortuous and braided collateral veins, usually smaller than the normal vein
Color Doppler: Useful to detect low echo or anechoic thrombus which may be missed on grayscale US • Duplex Doppler ultrasound is first line imaging investigation with sensitivity and specificity for acute symptomatic DVT between 90-100% • CECT and MR/MR venography are good non-invasive imaging tools for assessment of pelvic veins and IVC and for exclusion of pelvic and abdominal causes of DVT
Checklist for DVT
Thrombus is excluded if the vein is completely compressed
USF for varicose veins
Grayscale ultrasound: Allows de,f1mtlOnof vem lumen, vein valve leaflets and vem wall morph,ology • Assesses compressibility of the veir: and acoustIC properties of thrombus for evaluatIOn of age of thrombus • Pulsed Doppler: Differentiates venous from arterial flow • Documents venous flow pattern and flow direction • Allows timing of duration of venous reflux through incompetent valves • Color Doppler: Differentiates partial thrombosis from venous occlusion
Distinguishes reflux in the deep veins from reflux in the superficial system at the saphenofemoral junction and saphenopopliteal junction
Identifies incompetent perforating veins , “ , • Demonstrates recanalization of chronically thrombosed venous segment and collateralization a 0 nd thrombosed veins • B~S~imaging tool: Combination of grayscale, pulsed Doppler and color Doppler ultrasound
