Chapter 83 - Lower extremity aneurysms Flashcards by Gary Yang

M:F ratio of LE true aneurysms

30:1

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Association of AAA with other peripheral aneurysms

Femoral: 50-90%
One popliteal 30-50%
Bilateral popliteal 70%

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Chance of bilateral aneurysms in femoral and popliteal

Femoral: 25-50%

Popliteal 50-70%

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Rate of femoral or popliteal aneurysm in men or women with aortic aneurysms

14% in men

no association in women

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Normal size of CFA

Men 1.0 cm

Women 0.8 cm

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Indicated diameter for repair in CFA aneurysm

5 cm according to largest reported series 172 patients

3. 5 cm according to Lawrence

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Risk for CFA true aneurysms

1) men
2) age >70
3) smoking
4) HTN

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Cause of CFA true aneurysm

1) degenerative
2) atriomegaly
3) Behçet
4) Parkes Weber syndrome
5) Wegener granulomatosis

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distribution of true aneurysms in the femoral segment

CFA 81%
SFA 14%
PFA 5%

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Clinical presentation of true femoral aneurysm

Asymptomatic 30-40%
Pain 30-40%
Lower extremity ischemia (embolization) 65%

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Pain associated with femoral aneurysm

localized tenderness
compressive neuropathic pain
leg edema

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Indication for treatment of femoral aneurysm

1) all symptomatics

2) > 2.5 cm (controversial, maybe 3.5 cm according to Lawrence)

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Natural history of femoral pseudoaneurysm

Less than 2-3cm may thrombose spontaneously
Closure rate higher if less than 1.8 cm
Will not close if on anticoagulation

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Duplex Sen and Spe for pseudoaneurysm

Sensitivity 94%

Specificity 97%

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Ultrasound guided compression of femoral pseudoaneurysm first introduced in

1991

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Ultrasound guided compression of femoral pseudoaneurysm technique

1) compression maintained 10-20 min
2) repeat if flow still present
3) bed rest 6 hours
4) repeat DUS 24-48 hours

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Success rate of ultrasound guided compression; what if anticoagulated, time needed to compress and recurrence rate

66-86%
<40% if anticoagulation
Compression time 30-44 min
Recurrence 4%

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Contraindication for ultrasound guided compression of pseudoaneurysm

1) ischemic skin
2) infection
3) puncture site above inguinal ligament
4) severe pain
5) large hematoma

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Complication types and rate after ultrasound guided compression of pseudoaneurysm

2-4%

1) rupture
2) femoral vein thrombosis
3) femoral artery thrombosis
4) vasovagal

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Ultrasound-guided thrombin injection first described by

Cope in 1990’s using angiographic guidance

Kang modified using ultrasound guidance

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Thombin MOA

Converts fibrinogen to fibrin

Clot formation bypassing heparin/warfarin effects

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How to prepare thrombin

Bovine or human thrombin mix with NS

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Ultrasound-guided thrombin injection technique

1) US to identify cavity
2) local
3) puncture with 22 or 25 gauge needle
4) inject slowly via 3ml syringe over 10-15 seconds (1000 IU/ml): total dose ~ 1000 Units
5) bed rest 1 hour
6) repeat US 24 hours

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Ultrasound-guided thrombin injection success rate

96-100%

second injection in 7% cases

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Contraindication to bovine thrombin

1) allergy 2) infection 3) pregnancy Relative 1) wide channel/neck

Indication for open surgical repair of femoral pseudoaneurysms

1) ruptures 2) failure or contraindication to compression or thrombin 3) skin ischemia 4) AVF

Open repair techniques for femoral pseudoaneurysms

1) direct repair | 2) patch angioplasty

Complication following open repair of femoral pseudoaneurysms

Wound complication: 4-8% | Mortality 2.9%

SFA aneurysm (isolated)

Elderly men age 75.7 years middle third of artery mean diameter at presentation 8.4 cm

Clinical symptom of SFA aneurysm

Pulsatile tender thigh mass 59% Rupture 42% Distal ischemia 13%

When to fix SFA aneurysms

2.5 cm or greater

SFA aneurysm treatment outcome

Limb salvage 88% 5- year survival 62% Graft patency 85%

Rate of synchronous aneurysm in PFA aneurysms

70% | most common popliteal

PFA indication to repair

Whenever present since natural history unknown

Dissecting out PFA

1) vertical incision 2) start at CFA bifurcation 3) extent inferiorly and slightly laterally 4) sartorius and rectus femoris reflected laterally 5) divide crossing venous branches 6) preserve femoral nerve branches

Persistent sciatic artery prevalence

0.01-0.05%

Sciatic artery origin

Umbilical artery in embryology | at month 3 it regresses and becomes part of the inferior gluteal artery

Aneurysm formation in persistent sciatic arteries

40%

Symptoms of persistent sciatic artery aneurysm

1) enlarged butt mass 2) local compressive symptoms 3) distal ischemia

Repair of persistent sciatic artery aneurysm

Interposition graft without aneurysm resection given risk of sciatic nerve injury

Normal diameter of popliteal artery

0.5-1.1 cm

Size threshold for popliteal artery aneurysm

1.5 cm some say 2cm really need to know that popliteal artery size varies from proximal to distal

Popliteal artery aneurysm as a percentage of total peripheral aneurysms

70%

Popliteal artery aneurysm epidemiology

1) 7.4/100,000 men; 1/100,000 women 2) 50% have bilateral PAAs 3) 30-50% have AAA 4) 50% have another aneurysm somewhere in 10 years

Pathogenesis of popliteal artery aneurysms

Degenerative not atherosclerotic 1) disruption and fragmentation of elastic lamellae 2) decreased vascular SMC and increase pro-apoptotic signals also mechanical stress because of the location

Growth of popliteal artery aneurysms

< 20 mm: 1.5 mm/year 20-30 mm: 3 mm/yr >30 mm: 3.7 mm/yr

Risk factors for popliteal artery aneurysm growth

hypertension

Rupture risk of popliteal artery aneurysm

2.5% high rate of limb loss

Rate of LE complication in patients with popliteal artery aneurysms

32-74% in 5 years

Rate of rupture in popliteal artery aneurysms

2% (0-7%)

Symptoms of popliteal artery aneurysm rupture

1) swelling 2) edema 3) popliteal vein thrombosis 14%

Imaging modality in popliteal artery aneurysm

1) DSA helps with outflow but limited in terms of mural thrombus misleading 2) US easy 3) CTA MRA best

Risk of ALI and limb loss in popliteal aneurysm > 2cm

30-40%

When to repair popliteal artery aneurysms

1) symptomatic 2) asymptomatic 2-2.5 cm with thrombus 3) Extensive thrombus 4) occlusion of tibial vessels

Endovascular treatment of popliteal aneurysm criteria

1) proximal and distal landing 2cm 2) landing zone size consistency 3) no tortuosity 4) not extremely large aneurysm which could kink stent 5) cannot do in people who hyperflex knee routinely 6) must be on antiplatelet after 7) single vessel runoff has lower patency rate

Endovascular treatment for popliteal aneurysm technique

1) oversize 10-15% viabahn 2) ACT > 250 3) maximal 1 mm size differential between grafts if more than 1 used 4) avoid landing graft at the bend of the popliteal artery (few cm above actual knee joint; determined by doing angiogram with knee bent) 5) 2-3 cm overlap between stents 6) plavix indefinitely

John Hunter 1785 on popliteal aneurysm

Ligation of a coachman popliteal aneurysm

Medial vs posterior approach benefits in popliteal aneurysm

Medial: more proximal and distal exposure easier positioning Best for small fusiform aneurysms Posterior: better for large saccular aneurysms allow ligation of tributaries Allow excision of the mass effect

Medial approach to popliteal aneurysm rate of failed thrombosis

30%

What needs to be divided to gain proper access to the popliteal aneurysm via medial approach

Medial head of the gastrocnemius muscle

Posterior popliteal artery approach

1) Prone 2) Lazy S from medial proximal to lateral distal 3) palpate distal to adductor canal 4) Separate semimembranosus and semitendinosus from long head of bicep femoris 5) dissect on anterior surface of aneurysm to avoid injury to nerves (lateral posterior to aneurysm) 6) dissect down to two heads of the gastroc

Percentage of popliteal aneurysm that have acute ischemia on presentation

30%

Rate of patients without runoff after acute ischemia and popliteal thrombosis

25-45%

Rate of tpa infusion

2 mg/hr or less

Heparin infusion in sheath during tpa infusion

500 Units/hr

PTT and fibrinogen checks in tpa infusion

PTT < 50 | fibrinogen > 200 mg/dL (if it drops below then stop or reduce dose; stop if < 150 mg/dl)

Chance of thrombolysis in restoring runoff in popliteal thrombosis

77% at least 1

Preoperative thrombolysis in popliteal thrombosis in amputation rates

96% down to 69%

Limb salvage in popliteal aneurysms and primary patency | asymptomatic vs symptomatic

Asymptomatic Limb salvage 92% Primary patency 87% Symptomatic Limb salvage 80% primary patency 52%

Predictor of endovascular graft failure in popliteal aneurysm

Single vessel runoff

Patency of endograft in popliteal aneurysm

primary patency 5 year 70% secondary 76% better >80% if treated with plavix

Open vs endo repair of popliteal aneurysm

Open = longer LOS, higher 30d complication, better 3yr primary patency No difference in secondary patency or amputation rates

Reasons to choose endo over open for popliteal aneurysm

1) good anatomy 2) does not bend knee more than 90 degrees routinely 3) can take plavix >4-6 weeks

Tibial and pedal artery aneurysms key points

1) rare without trauma | 2) treatment: bypass if distal ischemia, ligation, coil embolization, observation and wait for spontaneous thrombosis