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Endovascular Treatment of Aortic Dissection
Acute aortic dissection causes death by rupture of the false lumen or by end-organ malperfusion. Untreated acute type A dissection has a mortality of approximately 50% within 48 hours, predominantly caused by rupture resulting in cardiac tamponade. Acute type B dissections have a mortality of approximately 25%, which doubles when the dissection is complicated by paraplegia or by renal, mesenteric, or lower extremity ischemia.
In recent years, numerous publications have described endovascular techniques for addressing the complications of acute type B and selective type A dissections, and as well as for elective and emergent procedures to treat chronic dissection. Endovascular techniques for treating aortic dissection fall into two classes: preventing rupture by excluding the false lumen by means of a carefully deployed endograft and treating malperfusion by correcting branch artery obstruction by means of an endograft or fenestration, supplemented by branch artery stents.
Role of Imaging
Despite the enthusiasm for endovascular treatment of aortic dissection, standard open repair of the uncomplicated type A dissection will remain the predominant life-saving procedure in this patient cohort for at least the next 5 to 10 years. Clinical examination and expeditious imaging of patients with transesophageal ultrasound or CT are the mainstay of early diagnosis of aortic dissection and of the triage of patients between emergent open repair versus medical or endovascular management.
High-quality cross-sectional imaging is critical for planning and performing endovascular procedures for aortic dissection. Features crucial for planning include evidence of contrast extravasation or contained rupture, location of large intimal tears, relation of tears to critical aortic branches, the identity and anatomic relation of the true and false lumens, the longitudinal extent of the dissection, the distribution of critical branches from the true and false lumen, the relation of the dissection flap to critical branch origins, and evidence of malperfusion.
Endovascular interventions can result in dramatic changes in the aortic anatomy and branch vessel perfusion. These changes include extension of dissection from type B to type A, tearing and intussusception of the aortic intimal flap, and collapse of the true lumen with new obstruction of branch arteries. Successful management of such complications requires prompt recognition of the presence and extent of the anatomic change, which requires intraoperative imaging by intravascular ultrasound (IVUS), transesophageal echocardiography (TEE), and angiography. IVUS provides the best mix of broad anatomic coverage, detection of changes in dissection flap configuration, and precise anatomic demonstration of the relation of the flap and vessel origins. Angiography allows assessment of branch artery perfusion flow and pressure. TEE is often used as an intraoperative monitor and gives information about changes in thoracic aortic anatomy similar to that from IVUS.
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