Atrial (A,B) and lateral (C,D) view of MV models of a healthy dog (A,C) and a dog affected by MMVD (B,D). Healthy dogs have a more elliptical annulus (A) while dogs with MMVD have a more circular one (B). Furthermore, in healthy dogs the saddle shape is more evident (C) than in dogs with MMVD (D) that have a smaller annulus height. Tenting height and tenting area are reduced in dogs with MMVD (D) compared to healthy dogs (C). Ao, aortic annulus; APD, antero-posterior annulus diameter; ALPMD, anterolateral- posteromedial annulus diameter; CmD, commissural diameter; LA, left atrial side of the valve; TnA, tenting area (dashed); AnH, annulus height; LV, left ventricular side of the valve; TnH, tenting height. Reproduced with permission from Menciotti et al., J. Vet. Cardiol.; published by Elsevier, 2017 [77].