On Pathophysiology and Treatment of Aortic Disease

Abstract: Pathophysiological processes underlying abdominal aortic aneurysm (AAA) formation and aortic dissections (AD) are largely unknown. Molecular imaging of the inflammatory component may improve our understanding of AAA and AD pathophysiology. The aims of this thesis were to evaluate the feasibility of positron emission tomography/magnetic resonance imaging (PET/MRI) to study in vivo pathophysiological changes of these aortic pathologies, and to study the outcomes after complex contemporary endovascular treatment thereof.In Paper I, we evaluated the feasibility of 18-F-fluorodeoxyglucose (FDG) PET/MRI to identify markers for inflammation in asymptomatic medium-large AAA. We identified FDG uptake and gadolinium enhancement (GE) in the aneurysmal wall, however FDG uptake corresponded rarely with mural inflammatory changes on MRI. In Paper II, we investigated whether inflammatory activity by means of FDG-PET/MRI can be detected in small to medium sized AAA, confirming the presence of inflammatory markers in the majority of patients. In Paper III, FDG-PET/MRI was used to characterize the inflammation and its transformation from acute to chronic phase in acute Stanford type B dissections. Highly increased FDG-activity was present in the dissected descending aorta in the acute phase, which markedly decreased over the course of a few months. MRI inflammatory changes were present in 60% of patients.In Paper IV, we evaluated the outcome and aortic remodelling after thoracic endovascular aortic repair (TEVAR) for chronic dissections. High rate of false lumen thrombosis occurred for dissections localized to the thoracic aorta covered by the stent-graft, but was more uncommon for extensive dissections distally. Aortic remodelling and sac shrinkage occurred in the thoracic aorta, but not distally. Reintervention rates were substantial (one third of cases). Paper V evaluated outcome of complex endovascular repair of post-dissection aneurysms of the arch and thoraco-abdominal aorta. Results were comparable to other recent reports using this new approach, however occurrence of retrograde Stanford type A dissection following arch fenestrated repair warrants caution.In conclusion, FDG-PET/MRI is a promising technique for studying inflammation in AAAs and ADs in vivo. For chronic aortic dissections, endovascular treatment results in good short-term outcome, but in the long-term re-interventions were common and adequate follow-up is thus of importance