Which one of the following occurs in ischemic cardiac tissue?

Loss of the myocardial blood supply leads to profound functional, biochemical, and morphologic consequences.Within seconds of vascular obstruction, aerobic glycolysis ceases, leading to a drop in adenosine triphosphate (ATP) and accumulation of lactic acid in the cardiac myocytes.The functional consequence is a rapid loss of contractility, which occurs within a minute or so of the onset of ischemia.Ultrastructural changes (including myofibrillar relaxation, glycogen depletion, cell and mitochondrial swelling) also become rapidly apparent. These early changes are potentially reversible.Only severe ischemia lasting at least 20 to 40 minutes causes irreversible damage and myocyte death leading to coagulation necrosis( Robbins Basic Pathology, 9th edition, page 377 )