Clinical implications of the biomechanics of bicuspid aortic valve and bicuspid aortopathy

Abstract

Bicuspid aortic valve (BAV), which affects up to 2% of the general population, results from the abnormal fusion of the cusps of the aortic valve. Patients with BAV are at a higher risk for developing aortic dilatation, a condition known as bicuspid aortopathy, which is associated with potentially life-threatening sequelae such as aortic dissection and aortic rupture. Although BAV biomechanics have been shown to contribute to aortopathy, their precise impact is yet to be delineated. Herein, we present the latest literature related to BAV biomechanics. We present the most recent definitions and classifications for BAV. We also summarize the current evidence pertaining to the mechanisms that drive bicuspid aortopathy. We highlight how aberrant flow patterns can contribute to the development of aortic dilatation. Finally, we discuss the role cardiac magnetic resonance imaging can have in assessing and managing patient with BAV and bicuspid aortopathy.

Keywords: 4D flow MRI; BAV-mediated hemodynamics; bicuspid aortic valve; bicuspid aortopathy; biomechanics.

Figure 1

Schematic representation of bicuspid aortic valve (BAV), as defined by Sievers and Schmidtke [modified from Sievers et al. (4)]. RCC, right coronary cusp; LCC, left coronary cusp; NCC, non-coronary cusp.

Figure 2

Abnormal bicuspid aortic valve (BAV) hemodynamics. (A) shows four patients with different BAV phenotype. Arrows point to regions where helical and abnormal flow patterns can be observed. (B) shows an example of regional wall shear stress in the ascending aorta. Four landmark locations are illustrated: left ventricular outflow tract, sinus of Valsalva, mid-ascending aorta, and distal ascending aorta. (C) shows anterior and posterior view from vectorial wall shear stress in RL and RN patients.

Figure 3

Abnormal helical flow and dilation. Flow patterns at peak systole were observed in a patient with RN fusion. Arrows point to regions with high helicity (white arrow) and vorticity (orange arrows), abnormal jet (white-golden arrows), elevated energy loss due to flow impingement (yellow arrow).

Figure 4

Personalized heat maps. A 60-year-old man with BAV Type 1 RL phenotype was scanned to obtain 4D flow velocities prior to surgical planning. Patient's velocity field was compared with an age and sex-match atlas allowing to identify abnormal regions (high wall shear stress in red, low wall shear stress in blue) of wall shear stress using heat maps.