B.41 Aortic Dissection Flashcards
B.41 Aortic Dissection
define
An aortic dissection is a tear in the inner layer of the aorta that leads to a progressively growing hematoma in the intima-media space.
Patients typically present with sudden onset severe pain radiating into the chest, back, or abdomen.
B.41 Aortic Dissection
Epidemiology
- Peak incidence: 60–80 years of age
- In patients with connective tissue disease: 30–50 y/o
- Sex: ♂ > ♀
B.41 Aortic Dissection
Acquired Etiology
- Hypertension (most common): Approximately 70% of patients with aortic dissection have elevated blood pressure, which can lead to dissection propagation and increases the risk of rupture.
- Trauma: This includes deceleration injuries from motor vehicle accidents or iatrogenic injuries related to valve replacements or graft surgeries.
- Vasculitis with aortic involvement: Conditions such as syphilis can affect the aorta.
- Substance Use: Use of amphetamines and cocaine is associated with increased risk.
- Pregnancy: Particularly during the third trimester or early postpartum period.
- Atherosclerosis: This condition can contribute to the risk of aortic dissection.
B.41 Aortic Dissection
Congenital Etiology
- Connective Tissue Disorders: Conditions such as Marfan syndrome and Ehlers-Danlos syndrome.
- Bicuspid Aortic Valve: Anomalies in the aortic valve structure that can increase risk.
- Coarctation of the Aorta: A congenital narrowing of the aorta that can contribute to complications.
B.41 Aortic Dissection
Localization
- Ascending aorta: ∼ 65% of cases
- Descending aorta, distal to the left subclavian artery: 20% of cases
- Aortic arch: 10% of cases
- Abdominal aorta: 5% of case
B.41 Aortic Dissection
Stanford classification
There are two classifications of aortic dissection to help direct management.
The Stanford classification categorizes aortic dissections based on their involvement of the ascending or descending aorta.
Stanford Type A Aortic Dissection: Any dissection that involves the ascending aorta (defined as proximal to the brachiocephalic artery).
- Can extend proximally to the aortic arch and distally to the descending aorta.
- Generally requires surgical intervention.
- Complications may include aortic regurgitation and cardiac tamponade.
Stanford Type B Aortic Dissection: Any dissection that does not involve the ascending aorta.
- Involves the descending aorta, originating distal to the left subclavian artery.
- Most cases can be managed with medical therapy (e.g., beta blockers, vasodilators).
B.41 Aortic Dissection
DeBakey Classification
The DeBakey classification (less commonly used) categorizes aortic dissections based on their origin and extent:
- Type I: Dissections that originate in the ascending aorta and extend to at least the aortic arch, typically reaching the descending aorta. Generally requires surgical intervention.
- Type II: Dissections that originate in and are confined to the ascending aorta. Generally requires surgical intervention.
- Type III: Dissections that begin in the descending aorta and often extend distally. Most cases can be managed with medical therapy.
- Further subdivided into:
- Type IIIa: Limited to the descending thoracic aorta above the diaphragm.
- Type IIIb: Extends below the diaphragm.
B.41 Aortic Dissection
Pathophysiology
A transverse tear in the aortic intima (called “entry”) allows blood to penetrate the media of the aorta, creating a false lumen in the intima-media space. This can lead to the formation of a hematoma that propagates downward.
- Rising pressure within the aorta can result in rupture.
- Obstruction of branching vessels (such as those supplying the coronary arteries, brain, kidneys, and lower limbs) can lead to ischemia in the affected areas.
- A subsequent intimal tear may cause a “reentry” of blood into the primary aortic lumen.
B.41 Aortic Dissection
Common anatomical sites of origin:
- Above the aortic root
- Aortic arch
- Distal to left subclavian arter
B.41 Aortic Dissection
Clinical features:
- Sudden and severe tearing/ripping pain
Location
- Anterior chest (ascending) or back (descending)
- Interscapular or retrosternal
- Neck and jaw
- Abdomen or periumbilical, colicky pain
Character: Pain may migrate as the dissection propagates downward.
- Hypertension or hypotension
- Asymmetrical blood pressure and pulse readings between limbs
- Syncope, diaphoresis, confusion, or agitation
- Presence of a heart murmur (indicative of aortic regurgitation in proximal dissection)
B.41 Aortic Dissection
ECG findings
Diagnostics
ECG
- Should be performed for all patients. Findings can be variable and may include:
- Normal results
- Signs of left ventricular hypertrophy
- Nonspecific changes, such as ST segment depression and T-wave alterations
B.41 Aortic Dissection
Lab
elevated D-dimer
B.41 Aortic Dissection
Imaging
GOLD STANDARD: Computed tomography angiography
Initial Imaging in Low to Moderate Risk Patients
- Chest X-ray (AP View)
- Characteristic findings may include: normal appearance, widened mediastinum, alteration of the mediastinal contour on serial imaging, mediastinal mass, calcium sign (displacement of the intimal calciums > 6 mm).
Additional Findings:
- Possible presence of double aortic contour, pleural cap, effusion, blurring of the aortic knuckle, tracheal shift, or widening of the paratracheal stripe.
Definitive Imaging
- CT Angiography of the chest, abdomen, and pelvis
- Magnetic Resonance Angiography (MRA) of the chest, abdomen, and pelvis
- Transesophageal Echocardiography (TEE)
The identification of a false lumen is highly suggestive of aortic dissection.
B.41 Aortic Dissection
Surgical Treatment:
Indications:
- All patients with Stanford A dissection
- Patients with Stanford B dissection who develop complications
Procedure:
- Open Surgery: Involves replacing the dissection with a polyester graft implantation.
- Endovascular Treatment: Aortic stent implantation (applicable only in type B dissections, especially if the open operative risk is deemed too high).
Important Note: Ascending aortic dissection is a surgical emergency!
B.41 Aortic Dissection
Medical therapy for Hypotensive pts
Hemodynamic Support:
Target Mean Arterial Pressure (MAP): 70 mm Hg or euvolemia.
Vasopressor Support: When the patient is hypotensive.
Medications:
Norepinephrine
Phenylephrine
Note: Avoid inotropes, as they may increase shear stress on the aorta by enhancing the heart’s contractility.
Identify and address any comorbidities:
Cardiac tamponade
Severe aortic regurgitation
Expedited operative management.
Avoid inotropes as they can worsen aortic wall stress.
B.41 Aortic Dissection
Medical therapy for Hypertensive pts
Target Systolic Blood Pressure (SBP): 100–120 mm Hg and Heart Rate (HR): ≤ 60 beats per minute.
Initial Treatment:
Administer an IV beta blocker to avoid reflex tachycardia (e.g., Esmolol, Labetalol).
Follow up with:
Vasodilator (e.g., IV sodium nitroprusside).
If BP is controlled: Start a Calcium Channel Blocker (CCB), such as Verapamil or Diltiazem.
For patients with descending aorta dissection: Those who remain stable on IV treatment can be transitioned to oral medications and discharged with ongoing outpatient monitoring.
B.41 Aortic Dissection
Complications
Aortic Rupture and Acute Blood Loss:
- Presents as back and flank pain (tearing pain), along with symptoms of shock.
Complications of Stanford Type A Dissections:
- Aortic Regurgitation: Extension of the dissection into the aortic valve.
- Cardiac Tamponade: Caused by fluid accumulation around the heart.
- Pericarditis: Extension of the dissection into the pericardium.
- Stroke: Involves extension of the dissection into the carotid arteries.
Complications of Both Stanford Type A and Stanford Type B Dissections:
Thoracic Complications:
- Bleeding into the thorax, mediastinum, and abdomen.
Vascular Complications due to Ischemia:
- Visceral Arteries:
- Celiac trunk, superior/inferior mesenteric arteries leading to abdominal ischemia and ischemic colitis.
Renal Arteries:
- Can result in acute renal failure (oliguria/anuria).
Spinal Arteries:
- Weakness of lower extremities or paraplegia due to compromised blood flow.
Complete Occlusion:
- Involvement of the distal aorta can lead to Leriche syndrome (aortoiliac occlusive disease).
B.41 Aortic Dissection
Prognosis
Prognosis
- In-hospital mortality rates for aortic dissection vary from 9% to 39%, influenced by the type of dissection and the treatment approach.
B.41 Aortic Dissection
Prevention
- Blood Pressure Control: Maintaining optimal blood pressure levels.
- Smoking Cessation: Stopping smoking to reduce risk factors.
