Is aortopathy in bicuspid aortic valve disease a congenital defect or a result of abnormal hemodynamics? A critical reappraisal of a one-sided argument

Abstract

Although there is adequate evidence that bicuspid aortic valve (BAV) is an inheritable disorder, there is a great controversy regarding the pathogenesis of dilatation of the proximal aorta. The hemodynamic theory was the first explanation for BAV aortopathy. The genetic theory, however, has become increasingly popular over the last decade and can now be viewed as the clearly dominant one. The widespread belief that BAV disease is a congenital disorder of vascular connective tissue has led to more aggressive treatment recommendations of the proximal aorta in such patients, approaching aortic management recommendations for patients with Marfan syndrome. There is emerging evidence that the 'clinically normal' BAV is associated with abnormal flow patterns and asymmetrically increased wall stress in the proximal aorta. Recent in vitro and in vivo studies on BAV function provide a unique hemodynamic insight into the different phenotypes of BAV disease and asymmetry of corresponding aortopathy even in the presence of a 'clinically normal' BAV. On the other hand, there is a subgroup of young male patients with BAV and a root dilatation phenotype, who may present the predominantly genetic form of BAV disease. In the face of these important findings, we feel that a critical review of this clinical problem is timely and appropriate, as the prevailing BAV-aortopathy theory undoubtedly affects the surgical approach to this common clinical entity. Thorough analysis of the recent literature shows a growing amount of evidence supporting the hemodynamic theory of aortopathy in patients with BAV disease. Data from recent studies requires a reevaluation of our overwhelming support of the genetic theory, and obliges us to acknowledge that hemodynamics plays an important role in the development of this disease process. Given the marked heterogeneity of BAV disease, further studies are required in order to more precisely determine which theory is the 'correct' one for explaining the obviously different types of BAV-associated aortopathy.

Altered aortic shape in bicuspid aortic valve relatives influences blood flow patterns

“…Nevertheless, increased vortex flow provides the potential haemodynamic basis for the development of aortopathy. 18,39,40 Our findings suggest that BAV relatives are more likely to have altered aortic shapes associated with abnormal aortic blood flow patterns, which have been associated with pathologic aneurysmal dilatation. Additional studies in larger cohorts are warranted to investigate the impact of aortic shape on flow patterns in the absence of valvular disease.…”

Aortopathy pathophysiology features in patients with bicuspid aortic valve.

“…в настоящий момент гемодинамическая теория аортопатии при ДАК занимает одно из главных мест в патогенезе [65]. S.Pastaи др.…”

Valve-Sparing Aortic Root Replacement and Aortic Valve Repair

“…This may be due to a combination of 1) genetic predisposition, whereby the aortic tissue weakness and fragility responsible for dilatation is a manifestation of a development defect afflicting both the aortic valve and wall and 2) the haemodynamic abnormality caused by a bicuspid valve such as eccentric turbulence is responsible for aortic dilatation. Although there is widespread support for the genetic theory, some debate still exists as to which process exerts the most dominant effect [7]. …”