• Aortic aneurysm
• Bicuspid aortic valve
• Aortic and arterial disease

We read with great interest the manuscript by Egbe and coauthors from Mayo Clinic published in Heart.1 The authors focused on a clinically relevant manifestation of intracranial aneurysms (IAs) in patients diagnosed with a bicuspid aortic valve disease (BAV). A large institutional BAV cohort was retrospectively analysed while identifying those patients with BAV who had brain imaging with MRA. A total of 52 patients (7.7%) with IA were identified which were associated with seven adverse events during the follow-up (two aneurysm ruptures, four coil embolisations and three aneurysm enlargements >1 mm). Based on these findings, the authors stated an increased IA prevalence in patients with BAV, especially in those presenting with a concomitant aortic coarctation (ie, 12.9%). Furthermore, a clinically relevant association was revealed between proximal BAV-associated aortopathy and IA occurrence which may indicate a common pathophysiologic pathway in the aneurysm formation. Although the natural history of BAV-associated IA’s seems to be very comparable with such IAs in the general population, the authors suggest baseline brain MRI in all diagnosed patients with BAV, especially in those presenting with a concomitant aortic coarctation and females with a right–left cusp fusion. From a practical point of view, this recommendation seems to be very reasonable, considering the fact of increased risk of concomitant cardiovascular anomalies in patients with BAV, including proximal aortopathy, coarctation, left ventricular outflow tract and coronary artery anomalies.2 3 A screening cardiovascular MRI examination including brain imaging may provide an excellent ‘one-stop’ method of evaluating aortic valve morphology, aortic root/ascending aorta dimensions and distal vascular tree. Furthermore, it is a well-established diagnostic tool for subsequent follow-up studies and represents an inherent part of our current diagnostic protocol in the specialised BAV outpatient units.

However, a thorough analysis of previously published literature points out several controversial issues that need some further clarification. Although incidental IA has been reported with a prevalence of 0.35% (95% CI 0.13 to 0.67) on brain MRI in the general population, these studies did not include individuals with thoracic aortic aneurysms, concomitant cardiovascular malformations and known connective tissue disorders.4 Given high prevalence of concomitant aortopathy (ie, 40–70%) in patients with BAV, the more frequent occurrence of IAs in BAV cohort might be only a marker of a more generalised arteriopathy/aortopathy rather than an indicator of BAV morphology itself. Of note, several retrospective studies revealed high prevalence (ie, 35/158 (22%)) of IAs in patients presenting with thoracic aortic aneurysms and dissections.5 In accordance with this finding, a total of 13–17% patients diagnosed with thoracic aortic aneurysms had concomitant IAs,6 while most of the patients with BAV and concomitant IA had a dilated thoracic aorta (ie, 5/6 (83%)).7 Until now there are no systematic prospective studies investigating the prevalence of IA in patients with thoracic aortic aneurysms/dissection in the setting of ‘normal’ tricuspid aortic valve (TAV), and, therefore, the question of causality between BAV, aortopathy and occurrence of IAs cannot be conclusively answered.

Furthermore, previous studies demonstrated very inhomogeneous findings regarding BAV prevalence in patients diagnosed with IA which are in the range between 0.6% and 10% (table 1). Such an inconsistency might be at least partially explained by the heterogeneous nature of BAV disease that may become manifest in different types of aortopathy (ie, so-called BAV phenotypes). Based on our personal experience, those patients with BAV presenting with a regurgitation of BAV and root-type dilatation of the proximal aorta (so-called root phenotype) might have a severe congenitally triggered aortopathy and, therefore, may be of particular interest for an accelerated IA formation.8 These root-phenotype patients with BAV are very different in their presentation compared with those patients presenting with BAV stenosis and an eccentric dilatation of the tubular ascending aorta. Given this marked heterogeneity of BAV disease, specific BAV phenotypes might be hypothetically associated with a different potential for IA formation. Due to quite infrequent coexistence between BAV and IA, only a large population-based longitudinal study comparing IA prevalence in BAV versus TAV entities, with and without concomitant aortopathy, could potentially provide a reliable answer to this intriguing question.