The effects of stretch and pressure have been demonstrated to affect the production of ECM components in the aortic valve.1, 2, 9 In a recent study by Rathan and colleagues, porcine aortic valve cusps exposed to AF and VF showed changes in the thickness of the fibrosa in response to AF.20 This corresponded to histological changes in expression of collagen and elastin. Here, ELN is linked to atrial fibrillation.