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Bay Four

          Patterns, pearls and practical medicine

Aortic dissection

  • 50% of dissections occur in those aged < 60 years (especially if inherited component). Most common in 70s and 80s though.
  • 65% occur in men
  • Affected women tend to be older, with a lower BMI than affected men, and they are more likely to be diabetic
  • Women with dissections are also less likely than men to be smokers, or to have a bicuspid aortic valve
  • There’s an increased risk of dissection with larger aneurysms, root phenotype and longer ascending aortic length
  • Dissection is twice as common in the winter months, and more common in the morning
  • When the aorta dissects blood flows in 2 channels, including a false lumen (layers of aorta peel like an onion). This risks rupture and reduces blood flow to different organs
  • The process of dissection can last minutes, hours or days as the tear propagates
  • Type A (70%) – Involves ascending aorta. Usually needs surgery
  • Type B (30%) – Involves aorta beyond subclavian (descending and posterior). Back pain suggestive. More often medical management

Outcomes

  • Around 4000 cases a year in the UK (around 2500 die within 30 days)
  • 50% mortality in first 48 hrs
  • 50% of type A dissections die before they reach hospital
  • In-hospital mortality is 22% of type A dissections and 14% for type B
  • Survival rate after surgery is 80%
  • More people die of aortic dissection than road traffic accidents
  • Most die from tamponade or haemorrhage into the mediastinum
  • 7% of out of hospital cardiac arrests thought to be due to aortic dissection

Associations

  • 70% due to HTN or atherosclerosis
  • 30% have inherited component
  • Several important disease associations (all of which require echo surveillance)
  • Marfan’s syndrome
      • 5% of all dissections. 0.02% of population have Marfan’s so it confers a significant risk
      • Dissections can involve the aortic root, or descending and abdominal aorta (at diameters below usual surgical threshold)
      • Often treated with betablockers or ARB to reduce rate of aortic dilatation
      • Surgery indicated once aortic root >50mm (or >45mm with additional risk factors)
  • Bicuspid aortic valve
      • Affects 1% of the population, many don’t know their diagnosis
      • Highly heritable but not monogenetic (genetic testing not indicated in isolated bicuspid valve)
      • Dissection nearly 10x more common
      • Surveillance by echo once aorta >40mm
      • Consider surgery once aortic root >50mm when risk is around 10-fold higher (nearly 1% in the next 5 years)
  • Turners’ syndrome
      • 50% have cardiac involvement, including aortic dilatation, bicuspid aortic valve and coarctation
  • Noonan’s syndrome
  • Vascular Ehlers-Danlos
      • Rare, due to pathogenic variants in COL3A1 gene
      • Aortic dissection occurs in up to 10%
      • Often treated with long term with celiprolol (vasodilating betablocker)
  • Loeys-diatz syndrome
  • ACTA2-related heritable thoracic aortic disease
  • Coarctation
      • Associated with bicuspid aortic valve as well as aneurysms, and can occur with Turners
      • May present as uncontrolled HTN in a young person, with BP difference between the arms (HTN may persist after successful treatment)
  • Other
      • Aortitis (Bechet’s, Takayasu’s, GCA, syphilis, RA)
      • Pregnancy (especially last trimester or postpartum)
      • Extreme isometric exertion
      • Cocaine
      • Previous aortic surgery
      • Iatrogenic (cardiac surgery)
  • Notes on genetic causes and screening
      • May be syndromic or non-syndromic
      • A generation may be skipped if incomplete penetrance
      • The number of genes linked to non-syndromic heritable thoracic aortic diseases (nsHTAD) is growing, including those rarely associated with extra-aortic features such as MYLK, ACTA2, MYH11, and PRKG1
      • Refer patients for genetic screen if:
          • Aged < 60 and hx of thoracic aortic dissection
          • Aged < 60, aortic dilatation and no hx of HTN
          • Aortic dilatation with z score > 3
          • Aortic dilatation or dissection, and syndromic features of Marfans, Loeys-Dietz, or vascular Ehlers Danlos
          • Aortic dilatation or dissection, and family hx of thoracic aortic disease, peripheral/intracranial aneurysm or unexplained sudden death aged <40
      • Screening family members can involve an echo and genetic testing
      • If a patient has thoracic aortic disease, and risk factors for an inherited cause, but no family history or pathogenic variant on genetic testing, family members should still be screened by echo

Clinical features

  • Severe sudden chest pain (maximal at onset) radiating to back
      • Ask about the quality, intensity at onset and radiation of pain. Ask all 3 and your chance of thinking about dissection increases dramatically
      • Sudden, tearing pain has high specificity – worst severity is usually at onset
      • Can be also described as sharp
      • Radiates to the back in 30% (especially if dissection of the descending aorta)
      • Can subside, and radiation is common (not having pain when seeing patient does not exclude diagnosis)
      • Pain can vanish and recur in epigastrium or elsewhere (migrating pain occurs in 16%)
      • ACS is around 150 times more common as a cause of chest pain however
      • No pain at all in around 7%
      • Chest pain with neurological signs is suggestive (including CVA, paraplegia, syncope).
      • Often patients are vomiting, sweating and look sick
      • Signs of malperfusion – may be transient neurology, peripheral circulation, MI (usually inferior), bowel ischaemia
      • Occasionally abdo pain and hoarseness
      • AKI and intestinal ischaemia can occur
  • Examination findings
      • Hypertension, but with asymmetrical pulses and BP – differences in BP useful, but far from confirmatory. 20% normal people have a difference if > 20mmHg.
      • Shock – 15%
      • Signs of aortic regurgitation (AR murmur not very helpful however)
      • Signs of a pericardial effusion
      • Focal neurology present in 17%
      • Limb ischaemia
      • Abdominal tenderness
      • Worth checking old echos if diagnosis suspected – is there aortic root dilatation or a bicuspid valve?

Diagnostic difficulties

  • Around 40% don’t present in the typical way that gets picked up in the ED department
  • Dissection is correctly picked up clinically in 30% of cases
  • 33% are misdiagnosed – usually as ACS or PE, gastritis, musculoskeletal pain, anxiety
  • Aortic pain, BP differential and abnormal CxR is present in only 27% but has a high specificity. 96% have one of these findings.
  • In branch vessel occlusion symptoms can come and go – collapse, CVA like symptoms, ischemic limbs, ischaemic bowel.
  • CT scan is the only reliable way to diagnose
  • Some argue that rule out scoring systems probably no better than clinical acumen, however combining the aortic dissection detection risk score with a d-dimer is often used to rule out acute dissection
  • Aortic Dissection Risk Score
      • Based upon medical history, pain features, examination findings
      • If score 2 or more – proceed to CT aorta
      • If score 0 or 1, do d-dimer, ECG to exclude STEMI, POCUS if available and CxR
      • If d-dimer positive, or CxR/echo suggestive – CT aorta
      • If d-dimer and CxR negative, can r/o dissection
  • Alternatively, some adopt a policy of scanning anyone with chest pain and at least one of:
      • A high-risk condition for dissection – Marfan’s, another associated CTD, aortic valve disease, family hx etc
      • High risk pain features – Sudden onset, severe, tearing/ripping, radiating to back
      • High risk clinical findings – Pulse deficit, BP differential >20 in both arms, neurology, AR murmur

Investigations

  • ECG can be normal, may see ST changes (especially inferior), or signs consistent with tamponade. Normal ECG in 22%. 0.1% of STEMIs are dissections.
  • CxR
      • Probably only normal in 15%
      • Widened mediastinum (>8cm on PA film, or about 60%)
      • Abnormal aortic contour (50%), ring sign (displacement of aorta >5mm past calcified aortic intima) / calcium sign (in type B)
      • Pleural effusion/haemothorax, or left apical opacification
      • Deviation of trachea and left main bronchus
      • Sensitivity 64%, specificity 86%
      • Rules out other causes of chest pain, but if you suspect dissection you need a CT anyway
  • Echo
      • Sensitivity around 90% for diagnosing type A and 40% of type B (may see AR and dilated aortic root, pericardial effusion, dissection flap).
      • TOE more sensitive (99%)
      • Can identify complications eg AR, tamponade, RWMA
      • POC echo might be faster than CT
      • TOE can be used in unstable patients who cannot go to CT
  • CT aorta
      • Best test (sensitivity 100%, specificity 98%)
      • Best to do gated with ECG synchronisation (prevents motion artefacts which can resemble dissection flaps)
      • The non-contrast part of scan is useful to assess for intramural haematoma
      • Shows a dissection flap (the ‘tennis ball’ sign) due to appearance of the smaller true and larger false lumen
      • In some centres, 3% of CT aorta’s positive for dissection, and 42% pick up other pathologies (in comparison: diagnostic yield of CTPA for PE is 5-30%, and for CT head for neurosurgical lesion is 3%)
      • Sometimes advised to do CT neck to pelvis to check extension and complications
      • If PE and ACS in differential – can ask for a triple rule out CT
  • Bloods
      • D-Dimer often raised (but if normal does not exclude it)
      • Trop can be up

Management

  • Control BP tightly – aim systolic< 120
      • Try IV labetolol first (short half-life), also hydralazine or sodium nitroprusside
      • In cases of malperfusion (eg to spine or brain) may tolerate higher BP
      • Early arterial line
      • Analgesia will also bring down BP – give morphine
  • Aim HR < 60
      • Can use betablockers, or if contraindicated can use IV non-dihydropyridine CCBs
  • Crash blood
  • Correct coagulopathy
  • Cardiothoracic opinion
  • Type A – surgery (or consider palliation if not a candidate. Age should not preclude surgery)
  • Type B
      • Surgery if complicated type B dissection (50%) ie. ongoing pain > 12 hrs, limb ischaemia, refractory HTN, progressive aortic enlargement, extending dissection.
      • TEVAR vs open repair depending on anatomy
      • If uncomplicated but ‘high-risk feature’, and favourable TEVAR anatomy, and life expectancy > 5 years – TEVAR best
      • ‘High risk features’ include various radiological criteria (check ESC guidelines), or reappearance of pain/symptoms
      • All others (eg low risk and uncomplicated type B dissections, or unfavourable TEVAR anatomy) – treat medically, and do surveillance
  • Chronic type B dissection (ie 3 months after onset of symptoms)
      • Consider intervention if rapid expansion, malperfusion, rupture, descending aorta >60mm
      • Control BP
  • In pregnancy
      • Type A – Deliver infant if viable first, then repair aorta
      • Uncomplicated type B – conservative medical treatment

Complications

  • Circulatory collapse and death
  • Shock could be cardiogenic or hypovolaemic (mortality >50% if present)
  • Pericardial tamponade
  • Malperfusion – to brain, limbs, gut, kidneys, coronaries (MI). This should be seen as an indication to intervene, not a contraindication

Follow up

  • Long term survival good if survives surgery
  • Get annual scans afterwards with tight BP control. Avoid isometric / very strenuous exercise.
  • Genetic screen if aged < 55 (their 1st degree relatives too)
  • For TEVAR, frequent imaging advised (1, 6, 12 months, then annually for first 5 years)
  • Medically treated type B dissections also require frequent f/u imaging

 

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