Aortic dissection Flashcards
what is the aetiology of aortic dissection?
1.Acquired:
Hypertension (most common risk factor)
Approx. 70% of patients with aortic dissection have elevated blood pressure, which can lead to propagation of the dissection and increases the risk of rupture.
Exception: In patients < 40 years of age, less than 40% of cases are due to hypertension.
Trauma (e.g., deceleration injury in a motor vehicle accident, or iatrogenic injury during valve replacements or graft surgery)
Vasculitis with aortic involvement (e.g., syphilis)
Use of amphetamines and cocaine
Third-trimester pregnancy (or early postpartum period)
Atherosclerosis
2.Congenital:
Connective tissue disease (Marfan syndrome, Ehlers-Danlos syndrome)
Bicuspid aortic valve
Coarctation of the aorta
what is the stanford classification of aortic dissection?
1.Stanford type A aortic dissection: any dissection involving the ascending aorta (defined as proximal to the brachiocephalic artery), regardless of origin
Can extend proximally to the aortic arch and distally to the descending aorta
Generally requires surgery
Complications include aortic regurgitation and cardiac tamponade.
2.Stanford type B aortic dissection: any dissection not involving the ascending aorta
Descending aorta; originating distal to the left subclavian artery
Most cases can be managed with medical therapy (e.g., beta blockers, vasodilators).
Stanford A = Affects ascending aorta; Stanford B = Begins beyond brachiocephalic vessels
what is the Debakey classification?
-Type I: Dissections originate in the ascending aorta and continue to at least the aortic arch but typically as far as the descending aorta.
Generally requires surgery
-Type II: Dissections originate in, and are restricted to, the ascending aorta.
Generally requires surgery
-Type III: Dissections originate in the descending aorta and most often extend distally.
Most cases can be managed by medical therapy.
Can be further subdivided into:
Type IIIa: limited to the descending thoracic aorta above the level of the diaphragm
Type IIIb: extends below the diaphragm
what is the pathophysio of aortic dissection?
Transverse tear in the aortic intima (“entry”) → blood enters the media of the aorta and forms a false lumen in the intima-media space → hematoma forms and propagates longitudinally downwards
Rising pressure within the aortic wall → rupture
Occlusion of every single branching vessel (e.g., coronary arteries, arteries supplying the brain, renal arteries, arteries supplying the lower limbs) → ischemia in the affected areas (see “Complications” below)
A second intimal tear may result in a “reentry” into the primary aortic lumen.
what are the clinical features of aortic dissection?
-Sudden and severe tearing/ripping pain
Location:
Anterior chest (ascending) or back (descending)
Interscapular or retrosternal pain
Neck and jaw
Abdomen or periumbilical, colicky pain
Character: migrates as the dissected wall propagates caudally
Hypertension or hypotension
Asymmetrical blood pressure and pulse readings between limbs
Syncope, diaphoresis, confusion or agitation
A heart murmur (an aortic regurgitation in a proximal dissection)
what is the diagnosis for aortic dissection?
1.Assess the risk of acute aortic dissection using the aortic dissection detection risk score (ADD-RS).
- Check ECG in all patients to exclude other causes of severe chest pain. signs of left vent hypertrophy usally seen
2.1 Laboratory studies
D-dimer: elevated levels [9]
Evaluate for signs of end-organ damage: troponin, BMP, lactate
Pre-operative labs: CBC, type and screen, BMP, coagulation panel - Consider which imaging modality is indicated
CXR: low to moderate-risk patients
Widened mediastinum (> 8 cm) at the level of the aortic knuckle
Alteration of the mediastinal contour seen on serial imaging
Mediastinal mass
Calcium sign: displacement of the intimal calcification of > 6 mm
Additional findings that may be present
Double aortic contour
Pleural cap
Pleural effusion
Blurring of the aortic knuckle
Tracheal shift
Widening of the paratracheal stripe
b.Definitive imaging (e.g., CTA, MRA): high-risk patients, unexplained hypotension, abnormal CXR, no alternative diagnosis
ndications
All high-risk patients: ADD-RS score of 2 or 3
Moderate and low-risk patients (ADD-RS score of 0 or 1) with:
Unexplained hypotension
No other diagnosis to explain the symptoms
Any concerning features present on chest x-ray
Modalities [5]
CT angiography of the chest, abdomen, and pelvis [5]
Indications: stable patients, surgical planning
Advantages: very high sensitivity and specificity (considered to be the gold standard) [5]
Suggestive findings
Intimal dissection flap
Double lumen
Aortic dilatation
Regions of malperfusion
Aortic hematoma (high-attenuation)
Contrast leak: indicates rupture.
-Magnetic resonance angiography (MRA) of the chest, abdomen, and pelvis
Indications: stable patients, contraindications to CTA
Advantages:
Similar sensitivity and specificity to CTA, without radiation or contrast exposure
Can also be used to detect aortic valve pathology and LV dysfunction
Disadvantages:
Time-consuming
Contraindications: renal insufficiency, claustrophobia, metallic implants, pacemakers
Not widely available on an emergency basis
Suggestive findings: similar to CT angiography
-Transesophageal echocardiography (TEE) Indications: Unstable patients Intraoperative visualization Renal insufficiency or contrast allergy Advantages: Rapid; can be performed at the bedside Quick differentiation between thoracic aortic aneurysm and thoracic aortic dissection Disadvantages: dissection flap can be difficult to distinguish from artifact Findings may include: Dissection flap (with differential Doppler flow) Double lumen in the ascending aorta Thrombosis in false lumen Pericardial effusion Other: catheter angiography, ultrasound
what is the treatment for aortic dissection?
-Urgent cardiothoracic/vascular surgery consult
- Check ECG
- Check labs:
D-dimer
Pre-operative: type and screen, CBC, coagulation panel, BMP, troponin
- Assess risk and consider definitive imaging (see aortic dissection detection risk score)
- Consider indications for surgical repair (e.g., all type A dissection, type B dissection with complications)
-Blood pressure control: goal MAP 70
In hypotensive patients: fluids, vasopressors
In hypertensive patients: goal SBP < 120 mm Hg and HR < 60/min
Beta blocker (first-line)
Sodium nitroprusside if HR is < 60/min but SBP is still > 120 mm Hg after treatment with beta blockers
If there are contraindications to beta blockers, use nondihydropyridine calcium channel blockers.
- Supportive care: Pain management
- Continuous telemetry and pulse oximetry
- Frequently monitor blood pressure.
- Monitor urine output.
- Transfer to the ICU or OR.
Monitor for complications.
what are the complication of aortic dissection?
-Aortic rupture and acute blood loss: acute back and flank pain (tearing pain), symptoms of shock → indication for emergency surgery
-Complications of Stanford type A dissections Myocardial infarction (coronary artery occlusion) Aortic regurgitation (extension of the dissection into the aortic valve): new diastolic heart murmur and (exertional) dyspnea Cardiac tamponade combined with cardiogenic shock Pericarditis (slow extension of the dissection into the pericardium) Stroke (extension of the dissection into the carotids)
-Complications of both Stanford type A dissection and Stanford type B dissections
Bleeding into the thorax, mediastinum, and abdomen
Arterial occlusion followed by ischemia of the:
Celiac trunk, superior/inferior mesenteric artery → acute abdomen, ischemic colitis
Renal arteries → acute renal failure (oliguria, anuria)
Spinal arteries → weakness of lower extremities or acute paraplegia
Complete occlusion of the distal aorta → Leriche syndrome (aortoiliac occlusive disease)
how can you prevent aortic dissection?
Blood pressure control
Smoking cessation [5]
Screening and repair of rapidly expanding aneurysms (also see “Therapy” and “Prevention” sections in aortic aneurysms)
