Aortic disease

• Acute Aortic Syndrome consists of
  • • Aortic dissection (commonest)
    • Intramural haematoma
    • Penetrating aortic ulcer
    • Aortic pseudo-aneurysm
    • Traumatic or iatrogenic aortic injury
• Aortic atheroma
  • • Thickened intima, atheroma, sometimes mobile or ulcerated components
    • If severe (atheroma >4mm) or complex (mobile or ulcerated components) – much higher risk of CVA. Treat with statins and single anti-platelet
• Primary types of aortic aneurysm
  • • Abdominal
    • Thoracic

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Dilated thoracic aorta / thoracic aortic aneurysms (TAA)

• Usually diagnosed incidentally
• The aorta enlarges with age (by around 0.8mm/decade, and faster in women than men).
• Aneurysms more common in men (as is dissection) but degenerative TAAs grow faster in women and have a higher risk of dissection
• Definitions
  • • Body surface area, or height, is commonly used to normalise aortic dimensions
    • Ascending thoracic aortic dilatation defined as >22 mm/m²
    • Normograms or z scores compare measured to expected aortic diameter, however in practice, aortic root dilatation is suspected when aorta is >40mm in men and >36mm in women (Annual risk of dissection is around 4% once TAA is 57mm)
    • An aneurysm is defined as >1.5 x larger than predicted size, but ‘significant aortic dilatation’ is a term more commonly used
    • Saccular aneurysm – due to infection, penetrating atherosclerotic ulcer, trauma or inflammation. Higher risk
    • Fusiform aneurysm – usually due to a CTD
• Risk factors
  • • HTN (80%)
    • Genetics (20%)
    • Found in 25% of patients with bicuspid aortic valve
• Causes of TAA
  • • Root/ascending aorta/arch (70%) – Genetic causes, bicuspid aortic valve, sporadic, atherosclerosis
    • Descending aorta (30%) – atherosclerosis (most), aortitis (infectious or not), trauma, coarctation
    • TAAs can extend into the abdominal aorta: thoracoabdominal aortic aneurysm (of which there are 5 subtypes, with different risks)
• Causes of aortitis
  • • Large vessel vasculitis – GCA, Takayasu’s
    • Other rheumatological conditions – SLE, RA, Sarcoid, Behcet’s, Cogan’s syndrome, ANCA-associated vasculitides, HLA-B27 associated spondyloarthropathies, relapsing polychondritis
    • Infections – TB/mycobacteria, syphilis, salmonella, Q fever and brucellosis, staph and strep
    • Other – Idiopathic, peri-aneurysmal aortitis, retroperitoneal fibrosis
• Risks for rupture
  • • Underlying CTD/genetic cause
    • Diameter >50mm (and especially if >60mm) or fast rate of growth
    • HTN
    • Smoking and COPD
    • Symptoms
    • Chronic dissection
    • Old age
• Investigation
  • • Echo to screen for TAA
    • If diagnosed by echo, do an ECG-triggered cardiac CT or MRI (this will confirm max diameter, rule out isolated single sinus dilatation and provide a baseline)
    • Assess entire aorta if TAA diagnosed, and assess aortic valve
• Management
  • • Patients should be given standard CV risk reduction lifestyle advice, and also advised to limit isometric exercise
    • Treat HTN (target 120/80 if tolerated)
    • Metformin might reduce rate of growth in diabetics
    • Statin (unless low CV risk and non-atherosclerotic TAA)
    • Consider single antiplatelet
    • Some advice avoiding fluroquinolone antibiotics which may increase risk of rupture/progression
    • Consider surgery
• Surgery generally advised if ascending aorta/root >50mm (or descending thoracic aneurysm of >55mm, or thoracoabdominal aortic aneurysm >60mm)
  • • Stronger indications (lower threshold) for surgery include bicuspid valve, ascending aorta >55mm, young age, uncontrolled HTN, family hx of dissection, lower operative risks, patient also requires aortic valve replacement, high growth rate (>3mm/year), aortic length >11mm, coarctation, planning pregnancy
    • Type of surgery depends on location of aneurysm and other factors (TEVAR best for descending aneurysms if no CTD)
    • Endoleaks (5 types) can develop after TEVAR and EVAR – some require re-intervention especially in types 1 and 3. Always do a CT within first month post-op
    • Other complications include pseudo-aneurysms and graft infections
• Surveillance
  • • Echo or CT if aortic root/ascending aorta, CT for arch/distal thoracic aorta.
    • Can use echo for follow up but only if agreement between echo and CT (if >3mm difference, use CT)
    • Use same imaging to compare over time
    • CMR can also be used but less availability
    • If root/ascending aorta 40-44mm – echo annually, and then every 2-3 years if growth <3mm/year
    • If root/ascending aorta 45-49mm – annual echo
    • If root/ascending aorta >50mm and no intervention advised – echo every 6 months
    • If growth rate >3mm/year – echo every 6 months
• Prognosis – untreated descending thoracic aneurysm has 54% 5-year survival

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Intramural haematoma

• Haemorrhage within aortic media (+/- intimal disruption)
• 65% involve descending aorta
• Occurs at an older age than dissection on average but risk factors similar
• Symptoms also similar, but less risk of AR, malperfusion, and pulse deficit
• CT shows crescentic or circular aortic wall thickening in the absence of an intimal flap or aortic wall enhancement
• Can evolve into dissection (12%), and aneurysms
• Regression occurs in over 30%
• High mortality
• Managed similarly to dissection – medical treatment, surgery for type A, consider TEVAR for type B (especially if complicated or high-risk factures)

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Penetrating atherosclerotic ulcer (PAU)

• Often multiple present, most commonly in the descending aorta
• Mostly affects older male multimorbid smokers
• Often incidental finding (symptoms may suggest ulcer expansion)
• If symptoms – similar medical treatment as for dissection (eg analgesia, HR and BP control etc)
• Surgery advised for type-A PAU (these are rare, but high risk of rupture)
• For type-B PAU: Endovasular intervention often advised if haemodynamically unstable, contained/impending rupture, refractory pain, aorta >55mm, large pseudoaneurysm, intramural haematoma or high-risk imaging features
• If chronic / asymptomatic penetrating ulcer – medical treatment, surveillance, and consider intervention if significant growth of ulcer/aorta >55mm/high risk imaging features

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Aortic pseudo-aneurysm

• • Can be due to trauma, surgery or infection
  • Often symptomless
  • Can lead to rupture – so usually repaired regardless of size or position

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Mycotic aortic aneurysms

• Infected aneurysms – generally bacterial, despite the name (usually staph or salmonella, occasionally anaerobes or TB). Called mycotic because mushroom-shaped, not because they have a fungal aetiology (although very rarely they do)
• Can be due to
  • • Contiguous infection extending into the aorta (eg from vertebral osteomyelitis, intraabdominal infections/abscesses, pancreatitis)
    • Septic emboli eg IE (30%, this is the most common cause)
    • Infected pseudoaneurysms eg post trauma or drug injection
• Can arise form pre-existing aortic aneurysms or from healthy aorta
• Most commonly affects abdominal aorta, intracranial arteries, peripheral arteries and visceral arteries, in that order
• Most patients symptomatic at time of diagnosis
• Imaging can help differentiate inflamed aorta (aortitis) from infected aorta (mycotic AA)

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Abdominal aortic aneurysms (AAA)

• Can be suprarenal, pararenal, juxtarenal or infrarenal
• Generally an AAA is >30mm (and mean growth is 3mm/year)
• Risk of rupture rises exponentially depending on diameter
• Asymptomatic in 65%
• Often found incidentally
• The 10-year CV event mortality risk is 15 times higher than risk of rupture
• Causes
  • • Atherosclerosis
    • Media degeneration
    • Genetic disorders
    • Infection or inflammation (10%)
• Risk factors
  • • Europeans
    • Men (but 4x more likely to rupture in women)
    • Smokers
    • Family hx (relative risk about 2)
    • HTN is the most important risk factor (DM actually protects)
    • Old age
• Women with a ruptured AAA are almost always aged >75, and either smokers or hypertensive (or both)
• AAA growth is unpredictable (especially at larger sizes)
• 25% of patients with AAA also have a thoracic aortic aneurysm, and in 25% of AAA it extends down to common iliacs
• Screening
  • • Duplex US best (but do CT if evaluating for repair)
    • Men can self-refer as at higher risk
    • Indicated for men aged 66 and over, and consider for women aged 70 and over, if they have any of:
      • • COPD
        • Vascular disease – IHD, PVD, PAD, cerebrovascular disease
        • Family hx of AAA
        • Hyperlipidaemia, HTN, past/current smoker
• Management
  • • If AAA >5.5cm – refer to vascular, ideally reviewed in 2 weeks
    • If AAA >3cm – refer to vascular, ideally reviewed in 12 weeks
    • Consider family screening
    • CV risk reduction
    • Discuss risk of rupture vs risks of surgery (and explain that AAA growth can be a bit unpredictable)
    • Medical treatment – same as for TAA above
    • Consider planned surgical intervention once AAA >50mm in women and >55mm in men
• Surveillance US
  • • Required if no imminent surgery or if repaired via EVAR
    • If AAA >25mm scan every 4 years
    • If 30-39mm scan every 3 years
    • If 40-44mm scan every year
    • If >45mm scan every 6 months in women and every year in men
    • If >50mm in men scan every 6 months
    • Consider shorter intervals if rapid growth (eg >5mm in 6 months or >10mm in a year)
• Radiological signs of AAA rupture
  • • Retroperitoneal haematoma
    • High crescent sign
    • Tangential calcification
    • Thrombus fissuration
    • Contrast extravasation
    • Paraortic fat stranding
    • Calcification discontinuity
    • Draped aorta sign
• If rupture / imminent rupture
  • • Consider urgent transfer (within 30 mins) to regional vascular centre
    • Restrictive volume resus
    • EVAR usually best if female or men aged > 70, open repair more often done for men aged < 70.
    • Intraabdominal compartment syndrome can occur after repair or EVAR
• Elective repair
  • • Considered if symptomatic, if >40mm and has grown > 10mm/year, if >55mm in men or if >50mm in women
    • Life expectancy must be > 2 years
    • Consider exercise testing pre-op
    • Do not use risk assessment tools for individual patients when considering surgery
    • Usually open repair, occasionally EVAR (if abdominal co-pathology, or high operative risk)
    • CAD is leading cause of early death after AAA repair
    • Will need surveillance imaging afterwards (for endoleaks)