Dilated cardiomyopathy-induced disruption of basement membrane alters the lever systems acting on the heart.

Dilated cardiomyopathy (DCM) is considered the most common form of non-ischemic heart diseases. DCM, occurs in response to both non-genetic and genetic factors, and has been associated with cytoskeletal protein mutations, impairing the contractile apparatus of cardiac myocytes. However, the pathology underlying the marked left ventricular dilatation remains unclear. Moreover, patients with end-stage DCM show alterations in the composition of the extracellular matrix (ECM), and myocardial fibrosis even when the cardiac myocytes are intact. Therefore we hypothesize that DCM is a disease of basement membrane, which functions to support sarcomeric interactions with the ECM, and not only impaired cardiac contractility. We propose that under physiological conditions, the heart could be considered a second-class lever system. Disruption of the basement membrane in DCM would cause disarray in the alignment of cardiac myocytes and alteration in the second-class lever system of the heart. Thus, current inotropic agents show minimal or no effect on therapy as they target cardiac contractility rather than cardiac architecture and the lever systems of the heart.