4-dimensional flow patterns in the ascending aorta differ strongly between bicuspid and tricuspid aortic valves

Abstract

Objectives: Bicuspid aortic valves (BAV) and their associated complications often require both replacement of the aortic valve and the ascending aorta (AAo). The etiology of aortic wall disease, however, is unknown. It is controversial if either a genetic tissue defect or vessel disease secondary to altered blood flow is the underlying reason. This study compared flow patterns in the AAo of BAV patients to individuals with tricuspid aortic valve (TAV) using four-dimensional cardiovascular magnetic resonance (4D-CMR). Methods: Eighteen subjects with normally functioning BAV, without stenosis, regurgitation or aortic dilation were compared with 18 age and sex matched volunteers with TAV. 4D blood flow data of the AAo were obtained by CMR (spatial resolution=2.1×1.7×2.5mm3, temporal resolution=39.2ms). Derived 4D flow animations were then evaluated by three independent and blinded observers. Results: Abnormal helical flow in the AAo was seen in 85% of the BAV group (figure 1). In TAV altered flow was only found in 6%. Comparison of 4D flow patterns revealed a significant difference between BAV and TAV (p=0.0004). Conclusions: Patients with BAV but no concomitant valve disease have significantly different 4D flow patterns compared to patients with TAV. This altered flow may lead to increased stress upon the wall and thereby heavily impact the development of aortic dilation in BAV. These findings suggest that connective tissue defects may only be a secondary finding in these patients and aortic root replacement should not generally be performed.