Morphological variability of the atrioventricular valve cusps in the equine heart.
Authors: De Silva Margherita, Tagliavia Claudio, Galiazzo Giorgia, Gifuni Giovanni, Caiazza Michele, Chiocchetti Roberto, Grandis Annamaria
Journal: Equine veterinary journal
Summary
# Morphological variability of the atrioventricular valve cusps in equine hearts Whilst atrioventricular valve anatomy in humans and veterinary species is well characterised, comparable morphometric data for horses remain sparse, limiting understanding of normal variation and its relevance to acquired valve disease. De Silva and colleagues examined 20 structurally normal equine hearts to quantify the anatomy of the mitral and tricuspid valves, particularly the frequency and characteristics of accessory leaflets. Beyond the expected principal leaflets, accessory leaflets were identified in 39 of 40 valves examined (mitral: 2–6 leaflets; tricuspid: 1–4 leaflets), each fully separated from adjacent structures, narrower and thinner than principal leaflets, and predominantly (95%) sharing tendinous cords with neighbouring leaflets whilst only a minority (34%) possessed independent chordae tendineae. This findings establish that supernumerary leaflets represent a common anatomical feature in healthy equine hearts rather than a pathological anomaly, though the clinical significance—particularly regarding their association with valvular regurgitation and the impact of multiple commissures on haemodynamic function—remains undetermined. For practitioners involved in cardiac assessment or post-mortem examination, recognition that accessory leaflets constitute normal equine anatomy is essential to avoid misinterpreting their presence as evidence of pathology, whilst further investigation into whether these structures influence susceptibility to acquired valve disease would strengthen understanding of equine cardiac pathogenesis.
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Practical Takeaways
- •Accessory leaflets in equine atrioventricular valves are a normal anatomical variant that occurs in nearly all horses, not a pathological finding
- •Understanding normal valve morphology including accessory structures is important for interpreting cardiac ultrasound and pathology findings
- •Further research is needed to determine whether valve morphological variants correlate with functional valve disease or cardiac murmurs in clinical cases
Key Findings
- •Accessory leaflets were identified in 39 of 40 atrioventricular valves (97.5%), with 2-6 in mitral valves and 1-4 in tricuspid valves
- •All accessory leaflets were separated from adjacent leaflets at their insertion and were narrower and thinner than principal leaflets
- •95% of accessory leaflets shared tendinous cords with adjacent leaflets, while only 34% had their own specific tendinous cords
- •The clinical relevance of accessory leaflets and increased commissures in relation to valvular regurgitation remains unknown