Forme fruste or 'Incomplete' bicuspid aortic valves with very small raphes: The prevalence of bicuspid valve and its significance may be underestimated

Background: Bicuspid aortic valve (BAV) comprises a broad spectrum of phenotypes. The importance of BAV in thoracic aortic aneurysm management has been debated. A subtle phenotype of BAV has been identified recently that could impact this debate.

Methods and results: 101 consecutive patients with intact aortic valves operated in the setting of ascending aneurysm between January 2011-January 2014 were retrospectively identified. 20 were excluded because of valve calcification. 79 of 81 remaining had aortic valve phenotype described in operative reports, including tri-leaflet, bicuspid, and difficult-to-classify valves with small degrees of non-calcific fusion (raphe) at the commissures. Photographs of some three-leaflet valves with very small raphes were obtained. 18/79 (22.8%) had obvious BAVs and 61/79 (77.2%) were initially considered tri-leaflet valves. 18/61 (29.5%) of these had distinct but very small raphes and 12/18 (66.7%) involved the right/left commissure. Moderate or greater aortic insufficiency was found in 13/43 (30%) of patients with tri-leaflet valves, 8/18 (44.4%) with obvious BAVs, and in 9/18 (50%) three-leaflet valves with very small raphes. Retrospective review of computed tomography, magnetic resonance imaging and trans-esophageal (but not trans-thoracic) echocardiography sometimes identified very small raphes.

Conclusions: Three-leaflet aortic valves exhibiting very small raphes occur in the setting of thoracic aneurysm and aortic insufficiency and may represent forme fruste BAVs. They are sometimes identifiable with high-resolution valve imaging. Without accounting for forme fruste BAVs, the true prevalence and impact of BAV on aortic complications may have been historically underestimated. This entity warrants further study in a prospective multi-center registry.