Aortic Dilation in Bicuspid Aortic Valve Disease

Abstract

Background Ascending aortic dilation is important in bicuspid aortic valve disease (BAV), with increased risk of aortic dissection. We used cardiovascular magnetic resonance (CMR) to understand the pathophysiology better by examining the links between 3-dimensional flow abnormalities, aortic function and aortic dilation. Methods and Results 142 subjects underwent CMR (mean age 40 years; 95 with BAV, 47 healthy volunteers [HV]). BAV patients had predominantly abnormal right-handed helical flow in the ascending aorta, larger ascending aortas (18.3 ±3.3 vs. 15.2 ±2.2mm/m2, p<0.001), and higher rotational (helical) flow (31.7 ±15.8 vs. 2.9 ±3.9mm2/s, p<0.001), systolic flow angle (23.1 ±12.5 vs. 7.0 ±4.6°, p<0.001) and systolic wall shear stress (WSS) (0.85 ±0.28 vs. 0.59 ±0.17N/m2, p<0.001) compared to HV. BAV with right-handed flow and right-non coronary cusp fusion (n= 31) showed more severe flow abnormalities (rotational flow 38.5 ±16.5 vs. 27.8 ±12.4mm2/s, p<0.001; systolic flow angle 29.4 ±10.9 vs. 19.4 ±11.4°, p<0.001; in-plane WSS 0.64 ±0.23 vs. 0.47 ±0.22N/m2, p<0.001) and larger aortas (19.5 ±3.4 vs. 17.5 ±3.1mm/m2, p<0.05) than right-left cusp fusion (n=55). BAV patients with normal flow patterns had similar aortic dimensions and WSS to HV and younger BAV patients showed abnormal flow patterns but no aortic dilation, both further supporting the importance of flow pattern in the etiology of aortic dilation. Aortic function measures (distensibility, aortic strain and pulse wave velocity) were similar across all groups. Conclusions Flow abnormalities may be a major contributor to aortic dilation in BAV. Fusion type affects the severity of flow abnormalities, and may allow better risk prediction and selection of patients for earlier surgical intervention.

Aortic Valve Stenosis Alters Expression of Regional Aortic Wall Shear Stress: New Insights From a 4‐Dimensional Flow Magnetic Resonance Imaging Study of 571 Subjects

“…Similar to our study, maximum systolic WSS was found in different aortic regions for RL‐BAV and RN‐BAV. These findings were confirmed by Bissel et al and Mahadevia et al in larger cohorts (142 and 75 subjects, respectively) 7, 31. However, an important shortcoming of past studies is related to the use of manually positioned 2D analysis planes for the calculation of WSS, which resulted in limited coverage of the complex and asymmetric WSS distribution in the aorta.…”

Frequent Dilatation of the Descending Aorta in Children With Hypoplastic Left Heart Syndrome Relates to Decreased Aortic Arch Elasticity

“…Dilatation of the DAo may be due to abnormal aortic blood flow patterns such as vortex formation, which is known to increase wall shear stress 10, 11, 12. Because the dilatation involves the whole length of the DAo, it is distinct from a circumscribed poststenotic dilation, which is explained by the fast and turbulent flow behind a narrowing 13, 14.…”

“…First, the extreme size of the neoaortic root and the surgically reconstructed aortic arch (Figure 1) are likely to cause abnormal blood flow patterns (eg, enhanced helical flow or vortex formation) that affect the thoracic aorta by increasing wall stress, which can cause vessel wall dilatation. Other studies investigating aortic blood flow patterns (eg, increased vertical flow) in patients with bicuspid aortic valves or aortic aneurysms support this assumption11, 20; however, the consequences of the disharmonious shape of the aortic arch and blood flow patterns have not yet been studied by recently introduced CMR techniques (eg, 4‐dimensional phase‐contrast magnetic resonance imaging). The second interpretation considers the impact of an intrinsically increased stiffness of the aortic arch on CSA in a downstream segment of the DAo, independent of abnormal flow patterns.…”

Functional assessment of thoracic aortic aneurysms – the future of risk prediction?

“…68 Bissell et al compared helical flow patterns in BAV and TAV patients. 52 They found BAV was associated with abnormal right-handed helical flow, which correlated with higher rotational helical flow, higher WSS and larger ascending aortas. BAV with right-non cusp fusion and right-handed flow showed the most severe flow abnormalities.…”

“…51 BAV with fusion of the right and noncoronary cusps was shown to have higher WSS and larger ascending aorta size. 52 The ascending aorta is the commonest site of aneurysm formation in BAV. Mahadevia et al further sub-analysed regional WSS distribution in circumferential sub-sectors of the ascending aorta of patients with BAV compared to tricuspid aortic valve (TAV).…”