Abdominal Aortic Aneurysm

Management of AAA

Dr Nadeem Niyaz Jan
DNB, FRCS
Consultant Vascular Surgeon

Important facts

• Aneurysm – localized irreversible artery dilatation >50%.
• 95% AAA –infra-renal.
• 5-7% incidence population > 60 yrs.
• Commoner in white males - ? why.
• Other atherosclerotic manifestations do not have a racial predilection.

Why does it happen?

• Auto-immune reaction " macrophage activity – T&B lymphocytes invade arterial wall " activate proteolytic activity " degrade elastin & collagen " weaken arterial wall " aneurysm.
• Lowest levels of elastin & collagen in distal aorta just before bifurcation.

Why is it lethal?

• < 4 cm diameter – 10% rupture.
• 4-5 cm diameter – 25% rupture.
• > 6 cm diameter – 50% rupture in 1 year.
• Rupture has a 80% mortality.
• Surgical mortality < 5%.
• life expectancy – dramatically - AAA -1950 – 60 – 8.7 new AAA / 100,000 -1971 – 80 – 36.5 new AAA / 100,000.

Recent concept on rupture AAA

• Old concept – mechanical increase in size < ballooning < thinning of wall < rupture.
• Protein metalloproteinase – 9 - 5 times higher levels in wall of 5-7 cm aneurysms compared to 3-5 cm - break down of collagen within the wall of the aneurysm.
• Confusion regarding life threatening size will end and save many lives.
• Chlamydia pneumonae antigens.

Whom to screen?

• > 60 years.
• Smokers.
• COPD patients.
• Atherosclerotic patients with CAD.
• PHT.
• Family history.

How do they present?

• Mostly asymptomatic – 75%.
• Compression – bowel, ureter.
• Peripheral emboli.
• Back or abdo. Pain unreleaved by position.
• Shock – 20%.
• pulsatile abdomen mass left of midline between xyphoid & umbilicus – knees bent & during exhailing – 50% accuracy.

What investigations do I order and why?

• Plain AXR - AP + Lat – calcification –eggshell appearance seen in < 50% cases –This is not the first investigation.
• Ultrasound - initial test – presence & size – Gas and obesity hinder proper diagnosis – can’t detect leaks, rupture, branch artery and suprarenal involvement - ideal for screening patients.

Can AAA be Tt conservatively?

• Acute reduction in BP & pain killers.
• IV sodium nitroprusside.
• IV Beta-blockers – esmalol, labetalol, propranolol, metoprololv.
• BP maintained 100-120mmHg systolic.
• Beta-blockers – maintain HR – 60-80/min.
• Morphine sulphate IV for pain.

When to intervene?

• Aneurysm – rupture or suspected.
• Symptomatic or rapidly expanding.
• > 4 cm diameter.
• Complicated – embolism, occlusion.
• Atypical aneurysms – dissection, mycotic, seccular or inflammatory.

What should I tell relatives?

• Pre-hospital rupture – >50% die on way.
• Those who reach – mortality # 1%/min.
• Prognosis good - not in severe shock on arrival – get immediate resuscitation & surgical intervention.
• Fatal MI – elective repair – 4.7%.
• Non-fatal MI – elective repair – 16%.

Traditional Vs Endovascular graft

Traditional Vs Endovascular graft 2

How safe is traditional surgery?

• Mortality. < 5% - relatively safe
• Peri-operative MI.
• Hemorrhage.
• Renal failure
• Post-op ileus, bowel obstruction, ischemic colitis.
• Spinal cord ischemia.
• Lower limb ischemia - emboli.

Is endovascular grafting possible?

• Greatest mural diameter.
• Extent of aneurysm – proximal & distal necks + extension into iliacs.
• Tortuosity of aorta & intramural thrombus.
• Iliac anatomy – occlusion; IIA relation to aneurysm, size & tortuousity.
• Calcification of neck and iliacs.
• Femorals – calcification or occlusion.

Who qualifies for endovascular grafting?

• > 21 years – for written consent.
• Radiation exposure – postmenopausal or surgically sterile women.
• Anesthetic clearance.
• Life expectancy > 2 years.
• Pre-op angio – IMA not essential for intestinal perfusion.
• One IIA must be preserved – rectal flow.

This too has a learning curve.

• Peri-graft leaks - 8- 44%.
• Graft limb thrombosis – 1–10%.
• Renal artery occlusion – 6–12%.
• Femoral artery injury – 2-17%.
• Hemorrhage - 2-17%.
• Graft dysfunction - 6-23%.
• Graft deployment failure - 2-12%.
• Graft malposition - 2-20%.

How good are interventionalists today?

• Recent study – 50 cases – 47 (94%) successful – 3 conversion to open surgery.
• Perigrafts leaks – 33% - resolved spontaneously or coil insertion.
• 3 had graft occlusion – thrombolytic therapy successful.

Investigations in FU

• Conventional surgery – yearly with US.
• Endovascular grafting – Immediate post-op with CT 6 month after yearly.

Case presentation

• Rajbir Singh, 60 yrs male.
• Abdominal pain for years now worsening.
• Severe COPD + PHT + CAD.
• USS abdomen for abdo pain – 7cm AAA.
• Pulsatile abdominal mass – non tender.
• All peripheral pulses palpable to ankles.
• No complications – blue toe syndrome.