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We explore aortic dissection with Travis Hughes, vascular surgery fellow from the University of Kentucky, including classification, medical management, and nuances of the surgical perspective.
Takeaway lessons
- Type B dissections do not involve the heart or coronaries, but Type A vs B nomenclature is falling out of favor versus more anatomically specific labeling; this system helps characterize the gray area between the innominate and the left subclavian.
- The main sequelae of concern in type B dissection in end organ ischemia. This may be dynamic, due to movement of the flap to obstruct the feeding artery, or static, due to occlusion by thrombosis.
- Hypotension is unusual in type B dissection and should be a red flag for another factor, such as involvement of the heart (coronary dissection, tamponade), or rupture.
- Rupture is not a common event in dissection (as compared to aortic aneurysm), but can occur.
- Medical management of type B dissection involves controlling the impulse against the dissection flap by reducing heart rate and blood pressure. SBP <120 and HR <80 are reasonable standard goals, but should be customized somewhat to the patient; allowing higher goals in a pain-free patient, particularly one who is experiencing sequelae of relative hypotension may be reasonable.
- During initial presentation, impulse control may prevent dissection from extending over a period of hours. Later, once it has thrombosed and scarred, risk may be somewhat less.
- Dissection involving the renal arteries can be explored using doppler ultrasound in skilled hands.
- Focal neurologic deficit should prompt concern for both stroke, and (in the lower extremities) thrombosis.
- First line is usually an IV beta blocker for heart rate and either IV beta or calcium channel blocker for BP. Esmolol is a classic beta blocker, although involves a large volume of infusate, and is not always very effective. Labetalol and nicardipine are nice choices. Nitroprusside is usually a rescue.
- Favor the right radial artery for an arterial catheter, as the left arm will sometimes be needed for the repair.
- Transition to oral agents as they stabilize. A repeat CTA 5-7 days from admission (often prior to discharge) is usually appropriate.
- The most common indication for repair is aneurysmal degeneration at the dissection site. Extension of the dissection, in the setting of appropriate medical management, is less common although possible, and may also indicate the need for repair.
- The primary goal of repair is to cover the entry to the dissection, and potentially stenting to expand the true lumen. When there is involvement of the iliac arteries, stenting is usually needed there. Malperfusion to visceral vessels is often corrected with these maneuvers, but they can be specifically stented or thrombectomy performed if needed.
- Open repair of type B dissection has become vanishingly rare due to high morbidity and rare indication.
- Stenting of the aorta creates risk for spinal cord ischemia, so keep BP higher. Extremity neuro changes should prompt driving the MAP >90, naloxone, and IV steroids.
- Lumber drain placement probably reduces this risk, and can be placed either reactively or proactively. Neurosurgery and/or anesthesiology or interventional radiology may do this.
- Shorter ischemic time to organs or extremities, and baseline vasculopathy (which gives time for the body to develop a tolerance to it), portend better recovery after revascularization. Prolonged ischemia to extremities may require amputation or at least fasciotomies to prevent compartment syndrome.
- Aspirin and perhaps clopidogrel (with or without a load) will usually be needed post-operatively.
- Infection of long-standing grafts are not common but can occur. Contrast imaging and perhaps tagged WBC scans (nuclear scintigraphy) can identify these. Surgical removal may or may not be possible and tends to be morbid.