Peculiarities and Natural History of Type B Aortic Dissection

Abstract

Cardiovascular disease is the leading cause of death in most western societies, and is increasing steadily in many developed countries. Aortic diseases constitute a growing share of the burden. New diagnostic imaging modalities, longer life expectancy in general, longer exposure to elevated blood pressure, and the proliferation of modern non-invasive imaging modalities have all contributed to the growing awareness of acute and chronic aortic syndromes. All mechanisms that weaken the aorta’s media layers via micro-apoplexy of the vessel wall lead to higher wall stress, which can induce aortic dilatation and aneurysm formation, eventually resulting in intramural hemorrhage, aortic dissection, and eventually rupture. Chronic hypertension in particular affects the composition of the arterial wall, and causes thickening, fibrosis, calcification, and extracellular fatty acid deposition. In parallel, the extracellular matrix undergoes accelerated degradation, apoptosis, and elastolysis, with hyalinization of collagen eventually leading to intimal disruption. In light of both the risks and disadvantages of open surgery, endovascular strategies are emerging as valuable treatment options for complicated type B dissection, and are likely to improve the adverse prognosis of the natural history (in the setting of complications). Conversely, in stable chronic type B dissection, care, medical management, and surveillance can improve survival in a similar way to preventive stent-graft placement. Such evidence may encourage a complication-specific approach with the use of endovascular intervention, and highlight the need for blood pressure control in every case.