Innervation of the atrioventricular and semi-lunar heart valves: a review

Heart valves were historically considered passive structures that function through the haemodynamic forces created by the contraction and relaxation of the myocardium. However, research into valvular structures has revealed that heart valves are very complex, specialized structures that contain both smooth muscle cells and nerve fibres. This is particularly true for the atrioventricular valves, which are by far the most well studied to date. The various heart valves have been shown to contract independently during different moments of the heart cycle, suggesting that compensatory adaptation mechanisms exist to mediate the timing and efficacy of heart valve closure. These adaptations occur via different mechanisms, including neural mechanisms that influence the heart valves. Accumulating evidence continues to improve our understanding of the nerve fibres in the heart (adrenergic, cholinergic, etc.). Future studies will no doubt add to this exciting picture. Here, we review the current morphological knowledge of human and animal heart valve innervation, including discussions of the chordae tendineae and the papillary muscles, as well as the differences between the atrioventricular (AV) valves and the semi-lunar (SL) valves.