Contractility of the myocardium is determined by the interaction of contractile (actin and myosin) and regulatory (troponin and tropomyosin) proteins in the presence of calcium ions and chemical energy. The formation of the actomyosin complex is affected by the modulatory (C-, F-, M-proteins, actinins) and interstitial proteins (different types of collagens, glycoproteins, glycosaminoglycans, elastins). Cardiac hypoxia is accompanied by qualitative and quantitative changes in both collagenous (change in the proportion of different extracellular matrix proteins) and non-collagenous proteins (formation of different isomyosins and isoforms of actins or regulatory proteins). This remodelling of cardiac musculature influences significantly the process of contraction and relaxation in the hypoxic myocardium.