Predictors of Outcome in Acute Type B Aortic Dissection

Abstract

Acute aortic dissection is a life-threatening cardiovascular event which occurs in 2.9-4 per 100.000 people a year. Aortic dissection originates from a laceration of the intimal layer of the aorta, defined as entry tear, allowing blood inflow along the medial layer, which will separate both layers of the aorta. The Stanford classification is most commonly used and divides dissections into type A and type B. Type B aortic dissection (TBAD) typically involve the descending aorta. The primary objective of this thesis is to provide predictors, both clinical as radiologic, for the outcome in TBAD, in order to have a patient specific approach to decide on whom to intervene and whom to treat conservatively. Medical treatment is still the therapy of choice in these patients, but several subset of patients have been identified in the first part of this book that warrant additional attention. TBAD patients presenting with aortic arch involvement and those with intramural hematoma type B have proven to have comparable outcomes to “classic” TBAD, and medical therapy should be considered the best therapy available. Predictors of aortic growth and complications during follow-up remain a debated topic in aortic dissections, because of the high late mortality rates associated with this disease. Due to periprocedural complications, routine stent graft placement has failed to show to be beneficial in the short term and a more patient specific approach is warranted. Partial thrombosis of the false lumen, reduced number of entry tears and the involvement of branch vessels have shown to be predictors of aortic dilatation and these patients might benefit from preemptive stent graft placement. In addition we looked at predictors for outcome in patients treated with thoracic endovascular aneurysm repair of the descending thoracic aorta (TEVAR). TEVAR is widely adopted as it has proven to be a superior treatment option in patients with TBAD compared to open surgical repair. Patients with a patent false lumen status and branch vessel involvement are less likely to develop false lumen thrombosis and physicians should consider a more extensive procedure with extensive aortic coverage and more stent placement of the affected organ vessels. Development of new low-profile and more reliable devices will lead to a further increased use of TEVAR in TBAD. Especially, since a recent study showed that TEVAR in addition to optimal medical treatment is associated with improved 5-year aorta-specific survival and delayed disease progression in uncomplicated TBAD. Although these findings might suggest that preemptive TEVAR should be considered in all stable type B dissection patients, our studies showed that medical therapy alone can be sufficient in many patient, which is important for both the morbidity and mortality as for the related costs. To further stratify patients that benefit from these procedures, dynamic imaging and specific biomarkers will play a key-roll. Future studies using dynamic CT and 4D PC-MRI, which can both visualize and quantify flow characteristics in relationship to aortic expansion, will allow us to better understand the dynamics of this disease and the influence of endovascular therapies on this process