Histology of the tricuspid valve annulus and right atrioventricular muscle distance.

There was no continuous circumferential aggregation of collagen fibres in the right atrioventricular junction. The distance between the right atrial and ventricular myocardium was greater at the inferior side than that at the anterosuperior side, which might lead to more inferior annular dilation versus anterosuperior dilation. These anatomical features will be fundamental for future discussions of the suturing method used in prosthetic ring annuloplasty for tricuspid regurgitation.