Mitral valve disease is a common cause of heart failure and death [1] and, accordingly, mitral valve anatomy has been investigated since the early 20th century [2]. Emerging evidence suggests that the mitral valve is a complex structure including the left annulus, mitral leaflets, tendinous cords and papillary muscles [3], and that these components are dynamic [4] and therefore accessible for treatment [1]. On the other hand, leaflets are considered to be biologically passive and fixed, adapting to an enlarged or narrowed ventricle and therefore not a suitable target for treatment in mitral valve lesions [5]. However, mitral leaflets may remain too long or small or too stiff or flexible compared to the ventricle due to various pathologies [1]. For example, in mitral valve prolapse, the length and elasticity of the leaflets are typically increased [6], whereas in patients with myocardial infarction or dilated cardiomyopathy, leaflet area is inadequate compared to the dilated left ventricle, leaflets are stiff and undergo fibrosis [7]. Therefore, in repair or replacement procedures targeting the mitral valve, overlooked mitral leaflets may result in unsatisfactory treatment outcomes.

Transcatheter mitral valve repair methods (MitraClip; Abbott, PASCAL; Edwards Lifesciences) developed especially in the last 30 years have brought mitral leaflet anatomy to the forefront. Deciding on the suitability, planning and implementation of these approaches requires an excellent understanding of normal mitral valve anatomy and knowledge of the most common variants [8,9]. However, it is not only transcatheter techniques that rely on precise anatomical knowledge; surgical mitral repair techniques—such as leaflet resection, chordal replacement, or the Alfieri stitch—also demand detailed appreciation of leaflet and scallop morphology to ensure procedural success. Accordingly, we aimed to define the dimensions and morphological variants of mitral leaflets and scallops in fresh human hearts and to highlight their potential implications for surgical and transcatheter mitral valve repair procedures.