CONTENTS

• Epidemiology
• Symptoms
• Physical examination (including POCUS)
• Laboratory studies
• ECG
• Chest radiograph
• Clinical approach to the diagnosis
  • [1] When to consider dissection
  • [2] Dissection risk score
  • [3] Further evaluation for score of 0-1
• Radiologic approach
• Treatment
  • Anti-impulse therapy
  • The hypotensive dissection patient
  • Surgery
• Prognosis
• Related topics
  • Non-acute aortic dissection
  • Intramuscular hematoma & penetrating aortic ulcer
• Questions & discussion

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epidemiology

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typical epidemiology of aortic dissection

• Older age (typically ~50s-70s).
  • Type A dissection is more common in the ~50s-60s.
  • Type B dissection is more common in the ~60s-70s. (Sadhu 2023)
• Male predominance.
• History of hypertension (70%).

risk factors for dissection (especially among younger patients)

• Structural abnormality of the aorta or aortic valve:
  • Aortic aneurysm.
  • Bicuspid aortic valve.
  • Aortic coarctation.
  • Supravalvular aortic stenosis.
  • Turner syndrome, Noonan syndrome.
• Sympathomimetic use (e.g., cocaine, methamphetamine).
• Pregnancy & postpartum period (especially third trimester 3️⃣).
• Iatrogenic:
  • Cardiac catheterization (often distal, type B dissection). (Griffin 2022)
  • IABP (intra-aortic balloon pump).
  • TAVR (transcutaneous aortic valve replacement).
  • Cardiac surgery (often proximal dissection).
• Weak connective tissue:
  • Marfan syndrome
    • Marfan syndrome carries a 5% risk of aortic dissection.
    • Among aortic dissection patients <40 years old, about half have Marfan syndrome. (Vincent 2024, 34849689)
  • Ehlers-Danlos Syndrome type IV.
  • Loeys-Dietz syndrome.
  • Polycystic kidney disease.
  • Family history of aortic disease.
• Vasculitis:
  • Takayasu arteritis.
  • GCA (giant cell arteritis).
  • Rheumatoid arthritis.
  • Syphilitic aortitis.
  • Behcet disease.
  • Polyarteritis nodosa.

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symptoms

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pain (95%)

• [1] Abrupt onset in 85% (+LR 2.6). (38983974)
  • Pain is often most severe at onset (unlike angina, which may have a more crescendo onset). (34849689)
• [2] Tearing or ripping pain in 30-40% (+LR 10). (38983974)
• [3] Migratory pain in ~15% (+LR 7.6). (38983974)
• [4] Severe pain in 90%.
• Pain location may involve the chest, back, and/or abdomen: (Brown 2022)
  • Type A dissection: chest pain ~80%, back pain ~50%, abdominal pain ~20%.
  • Type B dissection: chest pain ~60%, back pain ~60%, abdominal pain ~40%.
  • Chest pain may radiate to the back or epigastrium.
• Painless dissection is rare but may be more likely among patients with older age, diabetes, aortic aneurysm, recent cardiac surgery, or altered consciousness. (Brown 2022)

syncope (~5-10%)

• The causes of syncope mirror the causes of aortic dissection with hypotension (discussed below ⚡️).
• Syncope occurs in 19% of type A dissection, compared to 3% of type B dissection. (Gaggin 2021)

ischemic manifestations 

• Neurologic symptoms (~20%):
  • Ischemic stroke in ~5% (mechanisms include large-vessel occlusion or thrombus embolism from dissection).
  • Transverse myelitis from spinal artery occlusion.
  • Paraplegia due to peripheral nerve ischemia (can mimic transverse myelitis, but prognosis is better). (Tubarco 2021)
  • Horner syndrome may occur (due to compression of sympathetic nerves within the carotid sheath if dissection extends into the carotid artery). 📖
• Myocardial infarction (7% of patients). 34849689
• Mesenteric ischemia (abdominal pain, bloody diarrhea).
• Limb ischemia (~30%).

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physical examination including POCUS

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traditional physical examination

hemodynamics

• Hypertension is common (especially type B dissection).
• Hypotension may also occur, including shock (especially type A dissection). ⚡️

BP differential

• >20 mm BP difference between arms is generally used as a cutoff.
• Specificity is poor: 20% of normal people may have a >20 mm BP deviation. (38983974)
• The gross absence of a pulse is less sensitive but more worrisome.

other findings on traditional physical exam

• Focal neurologic deficits.
• Cool or ischemic limb.

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POCUS

echocardiography

• Potential findings include the following. Overall, echocardiology has reasonable sensitivity for Stanford A dissections but will miss Stanford B dissections.
• Aortic regurgitation? (Occurs in ~60% of Type A dissections). (Sadhu 2023)
• Dilated aortic root? (Defined based on aortic outflow tract diameter; see section below.)
• Dissection flap seen?
• Pericardial effusion +/- tamponade?
• Bicuspid aortic valve?

SPEED protocol (Sonographic Protocol for Emergently Evaluating Dissection)

• 🏎️ The SPEED protocol is designed for rapid evaluation of aortic dissection based on the following three features. In one study, it had a sensitivity of 92% and specificity of 91%. (38010071)
• [1] Pericardial effusion (on parasternal long view).
• [2] Aortic outflow tract diameter >35 mm (measured from inner wall to inner wall, within 20 mm of the aortic annulus at end-diastole as shown below).
  • The normal aortic outflow tract diameter is 24-40 mm, so some patients with measurements >35 mm may be normal. This cutoff is designed to improve sensitivity rather than specificity.
  • Aortic outflow tract diameter >35 mm is sensitive for type A dissection, but it is also found in 8% of normal patients. (38010071)
• [3] Intimal flap (including transverse and sagittal scans of the abdominal aorta using a curvilinear transducer from the diaphragmatic hiatus to the bifurcation into the common iliac arteries). (38010071)

additional POCUS findings may include

• Dissection flap in other arteries (e.g., carotid, femoral, subclavian).
• Free fluid in the abdomen and/or left pleural effusion (rarely seen, reflective of aortic rupture).

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laboratory studies

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D-dimer

• A normal D-dimer has a negative predictive value of ~95% for aortic dissection. (Sadhu 2023)
• If there is a high index of suspicion for aortic dissection, imaging shouldn't be delayed to obtain a D-dimer.
• An aortic dissection score of 0-1 plus a normal D-dimer argues against a diagnosis of aortic dissection (with a sensitivity up to ~98%). (29030346)
• ⚠️ Note that D-dimer will not be elevated in patients with intramural hematoma or penetrating atherosclerotic ulcer (discussed further below ⚡️). (Sadhu 2023)
• Elevated D-dimer is nonspecific. Further discussion of the D-dimer test: 📖

labs to evaluate for complications of dissection

• Hemorrhage.
• Rhabdomyolysis (creatine kinase).
• Renal failure (creatinine).
• Bowel ischemia (lactate).

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ECG

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most common findings

• Left ventricular hypertrophy (LVH).
• Nonspecific changes.

OMI

• ~2% of patients with aortic dissection have OMI.
• The right coronary artery (RCA) is more often involved. However, the left main coronary artery may also be involved (but such patients may not survive long enough to be diagnosed).

NOMI

• Stress may cause NOMI, even if dissection doesn't involve the coronaries.

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chest radiograph

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mediastinal widening

• Sensitivity is limited (perhaps ~60%).
  • >6-8 cm is considered wide.
  • A comparison with a prior chest radiograph may help improve performance. (38983974)
• Tracheal deviation to the right may be seen.

aortic contour

• The aortic knob may be irregular, widened, or there may be a double aortic shadow. (39078908)
• Rarely, displacement of aortic calcification towards the middle of the aorta (>5 mm from the wall) may serve as a clue suggesting dissection.

left-sided pleural effusion

• Left-sided pleural effusion may rarely be seen.
• Causes of pleural effusion may include:
  • Hemothorax is due to a rupture of the aorta into the left pleura.
  • Exudative effusion due to inflammation. (34849689)

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clinical approach to the diagnosis of aortic dissection

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[1] when to consider aortic dissection?

• Pain (chest, abdomen, or back).
• Syncope.
• Ischemia (CNS, mesenteric, myocardial, or limb).

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[2] aortic dissection risk score 🧮

calculation of the aortic dissection risk score

• 1 point for any high-risk condition:
  • Marfan syndrome or other heritable aortic diseases.
  • Family history of aortic disease.
  • Known aortic valve disease.
  • Recent aortic manipulation (surgery or catheterization).
  • Known thoracic aortic aneurysm.
• 1 point for chest, back, or abdominal pain that is:
  • Abrupt onset.
  • Severe intensity.
  • Ripping or tearing quality.
• 1 point for any high-risk exam feature:
  • Pulse deficit.
  • Systolic Bp differential (>20 mm).
  • Focal neurological deficit (plus pain).
  • New aortic insufficiency murmur (plus pain).
  • Hypotension/shock.

interpretation of the aortic dissection risk score

• 0 = Low risk.
• 1 = Intermediate risk.
• 2-3 = High risk ➡️ Obtain immediate imaging (e.g., CT angiography).

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[3] further evaluation to risk of 0-1

Carefully consider the epidemiological risk factors and historical clues for dissection to refine your pre-test probability. Note that the aortic risk score doesn't include every potential finding that might be important. Management depends on whether you actually think the patient really might have a dissection or whether you're just trying to rule it out:  

[3a] If you do have a strong clinical concern for dissection

• Obtain a STAT CT angiogram.

[3b] If you don't have a strong clinical concern for dissection

• Obtain additional testing:
  • [1] SPEED protocol (using POCUS). ⚡️
  • [2] D-dimer. ⚡️
• If the D-dimer is normal and the SPEED protocol POCUS is negative, dissection has been excluded.
• If the D-dimer is elevated and/or the SPEED protocol POCUS is positive, further investigation is necessary (usually CT angiography).

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radiologic approach

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CT angiography (CTA) 🏆

• CT angiography of the aorta is generally the diagnostic test of choice.
• Advantages include:
  • Rapidly.
  • Widely available.
  • High sensitivity.
  • Allows for operative planning (e.g., allowing definition of the extent of dissection and which vessels are involved).
  • Evaluates other organs for acute pathology.
• Electrocardiogram-gated CTA may improve resolution at the aortic base, with a sensitivity approaching 100%. (36640801)

transesophageal echocardiography (TEE)

• Advantages:
  • Evaluation of valvular function.
  • Evaluation of ventricular function.
  • Portable.
• Disadvantages:
  • Logistically challenging in most contexts.
  • TEE is an invasive procedure that requires procedural sedation, which may be perilous (spikes in blood pressure could precipitate aortic rupture).
  • TEE doesn't allow evaluation of the ascending aorta at the level of the bronchi or the abdominal aorta.
  • TEE cannot evaluate all the great vessels.
  • Difficulty diagnosing intramural hematoma. (Griffin 2022)

MR angiography (MRA)

• Advantage: Excellent resolution of aorta and branch vessels.
• Disadvantages:
  • Logistical nightmare (usually not an option for emergent evaluation).
  • Contraindicated in patients with metallic implants.
• Role?
  • MRA is rarely helpful in an emergency context.
  • MRA may be utilized in rare situations where the diagnosis remains unclear after CT scan. (Schmidt 2024)

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anti-impulse therapy

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clinical targets

• [1] SBP (systolic Bp) ~100-120 mm. (Tubaro 2021, 36640801, 39078908)
  • ⚠️ Measure Bp using the limb with the highest blood pressure (some limbs may have occluded arteries).
• [2] Heart rate ~60-70 b/m.
  • ⚠️ Patients with severe aortic regurgitation may require a higher heart rate. (Schmidt 2024) In the context of aortic regurgitation, a slow heart rate leads to increased diastolic time, and blood spends more time regurgitating.
• [3] Adequate end-organ perfusion:
  • Intact mental status.
  • Adequate urine output.
  • Hemodynamic targets may need to be personalized based on chronic baseline blood pressure and organ perfusion.
• [4] Absence of pain: persistent pain may suggest ongoing dissection due to inadequate medical therapy.

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(#1) Analgesia

• Immediately ensure that pain is controlled (e.g., using titrated doses of IV fentanyl).
• Pain control itself will often lead to a prompt improvement in blood pressure.

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(#2) beta-blocker or diltiazem for target heart rate ~60-70 b/m

agent selection

• This often depends on which agents are most readily available.
• Esmolol may be preferred due to titratability.
• Labetalol causes a greater reduction in blood pressure as compared to most other beta-blockers, so labetalol could be helpful in patients with severe hypertension.
• Metoprolol causes less reduction in blood pressure, so it could be helpful in patients with predominantly tachycardia (with normal blood pressure or mild hypertension).
• Diltiazem could be utilized if beta-blockers are contraindicated (e.g., acute cocaine intoxication).

esmolol infusion 💉

• Esmolol has an onset of 1-2 minutes and a duration of action of 10-30 minutes.
• Dosing:
  • Loading dose = 0.5 mg/kg.
  • Start infusion at 50 mcg/kg/min.
  • For inadequate effect, re-load (0.5 mg/kg) and increase infusion by 50 mcg/kg/min. Up-titrate as needed to a max dose of 200 mcg/kg/min.

labetalol 💉

• Labetalol has an onset of 5-10 minutes and a duration of action of 3-6 hours.
• Labetalol has some advantages:
  • Labetalol is often more readily available.
  • Labetalol is an alpha-beta blocker, so it reduces blood pressure more than most other beta-blockers. This may be useful for patients with severe hypertension.
• Dosing:
  • Start with sequential pushes of 20mg, 40mg, 80mg, 80mg, and 80mg (q10 min PRN).
  • The effective dose may repeated PRN.

metoprolol 💉

• Metoprolol has an onset of ~5 minutes and a duration of action of several hours.
• Metoprolol has some advantages:
  • Often more readily available.
  • It may allow for control of heart rate without causing a substantial reduction in blood pressure (for a patient with tachycardia but only mild hypertension).
• Dosing:
  • Usually, start with 5 mg IV, which should take effect within ~5 minutes.
  • Additional doses may be given every 5 minutes, titrating to effect.
  • Generally, no more than 15 mg total will be used initially.
  • Repeat dosing may be provided every 3-6 hours. (Sadhu 2023)

diltiazem

• Indications for diltiazem:
  • Sympathomimetic intoxication.
  • Severe asthma.
• Initial bolus of 0.25 mg/kg over two minutes.
• Subsequent infusion of 5-20 mg/hr.

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(#3) vasodilator to target SBP < ~120 mm

• Clevidipine 💉 is generally ideal but not widely available.
• Nicardipine 💉 is another excellent option.

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(#4) transition to oral antihypertensives 

• After about a day, oral antihypertensives may be introduced to facilitate weaning off intravenous antihypertensives.
• Beta-blockers are the cornerstone of chronic therapy. (Schmidt 2024) Intravenous beta-blockers may be transitioned to oral beta-blockers (e.g., metoprolol or labetalol).
• Intravenous calcium channel blockers may be transitioned to oral calcium channel blockers (e.g., nifedipine-XR).

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the hypotensive aortic dissection patient

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🚨 This is highly worrisome since most patients should be hypertensive.  Hypotension occurs in up to 25% of patients with type A dissection but only <5% of patients with type B dissection. (38983974) 

differential diagnosis includes

• [1] Severe aortic regurgitation.
• [2] Hemopericardium with tamponade (note: acute tamponade can occur with low-volume effusions).
  • Tamponade from a chronic disease process (e.g., malignancy) may present with massive effusions due to gradual stretching of the pericardium.  In contrast, acute bleeding into the pericardium can cause tamponade with a relatively unimpressive effusion (because the pericardium has had no time to stretch open).
• [3] OMI due to occlusion of one of the right coronary artery (more often) or left main coronary.
• [4] Hemorrhage (e.g., ruptured aorta into left pleural space).
• [5] Pseudohypotension (falsely low Bp due to occlusion of limb artery by dissection flap).
• [6] Mesenteric ischemia.

evaluation

• Check BP in all extremities to exclude pseudohypertension.
• Bedside echocardiography.
• EKG to evaluate for occlusive MI.

treatment

• Most of these patients will require immediate surgery.
• Resuscitation with crystalloid or blood may be helpful for patients with hemorrhage or tamponade.
• Vasopressor infusion (e.g., norepinephrine) may help maintain adequate blood pressure. However, avoid hypertension or tachycardia (e.g., optimal heart rate of 60-80 b/m and MAP of ~65 mm).
• Tamponade can be temporized with pericardiocentesis if there is a delay in transfer to the operating room and the patient is actively dying. Blood may re-accumulate, so leaving a catheter in the pericardium may be ideal. If the pericardium is drained, be careful about rebound hypertension, which may promote worsening of the aortic dissection. (36640801)
• ⚠️ If echocardiography shows a clot in the pericardium, bedside drainage with a needle/catheter is impossible.

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surgery

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classification systems

• Stanford:
  • Type A = Involves the Ascending aorta +/- descending aorta.
  • Type B = Doesn't involve the ascending aorta (restricted to the descending aorta).
• Society of Thoracic Surgeons: The Stanford system was modified, delineating the precise areas of the aorta involved (figure above).
• DeBakey:
  • Type I = Starts in ascending aorta, propagates into descending & abdominal aorta.
  • Type II = Confined to ascending aorta.
  • Type IIIa = Confined to descending thoracic aorta.
  • Type IIIb = Involves descending aorta, extending into the abdominal aorta.

indications for intervention (surgery or endovascular)

• Sanford type A dissection (involvement of aorta proximal to the left subclavian).
  • A preoperative coronary angiogram usually isn't done (as it causes an unnecessary delay). (Gaggin 2021)
• Stanford type B dissection with complications:
  • Aortic rupture (e.g., hemothorax, peri-aortic hematomas).
  • The aorta expands with threatened rupture.
  • Occlusion of major arteries (e.g., mesenteric or limb ischemia).
  • Refractory pain. (Sadhu 2023)
  • Refractory hypertension.
• Patients who are initially managed medically require close monitoring for the development of complications that could require intervention.
• Cardiothoracic and/or vascular surgery should always be involved in determining the timing and selection of intervention(s).

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prognosis of acute aortic dissection

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Stanford Type A dissection

• Following surgery, 14-day mortality is 20% with surgery.
• Without surgery, 14-day mortality is 50%. (Tubarco 2021)

Stanford Type B dissection

• Uncomplicated dissection that only requires medical management: 14-day mortality is <10%.
• Complicated Type B dissection requiring endovascular repair: 14-day mortality is ~30%. (Tubarco 2021)

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non-acute aortic dissection

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• Classification of aortic dissection based on time after symptoms:
  • Acute aortic dissection: <2 weeks.
  • Subacute aortic dissection: 2 weeks – 3 months.
  • Chronic aortic dissection: > 3 months.
  • (American guidelines utilize six weeks as a cutoff between subacute and chronic dissection, whereas European guidelines use 90 days). (Vincent 2024)
• Without therapy, 70% of patients will die within the first two weeks. (Brown 2022) If a patient presents who has already survived for >2 weeks without therapy,  this reduces the likelihood that they will deteriorate.
• Surgery may not be required, even for an ascending dissection.
• Potential indications for surgery may include:
  • Recurrent pain.
  • Aneurysm formation.
  • Retrograde dissection extension to a proximal extent. (Griffin 2022)
• Serial CT angiography may be helpful in surveilling disease progression that could require intervention.

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intramuscular hematoma and penetrating aortic ulcer

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basics of intramuscular hematoma (IMH)

• Intramural hematoma is a hematoma within the wall of the aorta due to either:
  • (a) Rupture of the aortic vasa vasorum (small arteries coursing through the wall of the aorta).
  • (b) Evolution of a penetrating aortic ulcer (discussed below).
  • (c) Tiny dissection of the aorta, which subsequently seals itself (so the intimal tear is invisible).
• IMH is diagnosed in roughly ~15% of patients who are initially thought to have an aortic dissection. (Tubarco 2021)
• IMH usually has a more benign course than aortic dissection, but it isn't benign (Type A intramural hematoma carries ~30% in-hospital mortality). (35029783)  Potential complications of IMH include:
  • Extension into the aortic lumen leads to an aortic dissection. This may occur in roughly a third of patients with intramural hematoma within the ascending aorta. (Brown 2022; Sadhu 2023)
  • Aortic rupture and hemorrhage due to extension beyond the aorta. IMH are often located in the outer media near the adventitia so that they may have a greater tendency for rupture (compared to aortic dissection). (Mayo 5e)
  • Development of aortic aneurysm or pseudoaneurysm.

basics of penetrating aortic ulcer (PAU)

• Penetrating aortic ulcer (PAU) occurs when an atheromatous plaque erodes into the aortic media. The plaque generally prevents the ulcer from propagating along the vessel (as in a classical dissection).
• PAU is usually found in the mid-to-distal descending thoracic aorta due to the high rate of atherosclerosis at that location. (Griffin 2021)
• PAU usually occurs in older patients with extensive atherosclerotic disease. PAU is rare, accounting for only ~5% of acute aortic syndromes. (35029783)
• Potential complications may include:
  • Formation of an intramuscular hematoma.
  • Development of a pseudoaneurysm or true saccular aneurysm.
  • Aortic rupture. (Griffin 2022)
  • Aortic dissection can occur.

clinical presentation

• Presentation is often similar to an aortic dissection (e.g., sudden-onset, severe pain in the chest and/or back).
• Pertinent differences compared to patients with aortic dissection:
  • Pain doesn't migrate over time.
  • There aren't symptoms due to vascular occlusion (e.g., stroke, limb ischemia).

management

• Management is overall very similar to the treatment of acute aortic dissection as explored above. 
• Anti-impulse therapy should be utilized to control tachycardia and blood pressure (as described above ⚡️).
• Surgery should be consulted. Surgery may be indicated, especially for:
  • Larger lesions.
  • Involvement of the ascending aorta, especially intramuscular hematoma involving the ascending aorta (some sources recommend treatment of intramuscular hematoma similarly to aortic dissection). (35029783)
  • Enlargement over time; saccular aneurysm or pseudoaneurysm; impending rupture.
  • Persistent pain.
• Serial imaging can help detect progression that may warrant intervention (e.g., endovascular stent insertion).

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questions & discussion

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