Heart attack scar. Light micrograph of a section through heart tissue showing scarring from a heart attack (myocardial infarction). An infarction is tissue death (necrosis) caused by blockage of the tissue's blood supply (ischaemia). The scar is the pale pink and white fibrous tissue within the muscle tissue (myocardium) at centre. The pericardium (double-layered membrane surrounding the heart) is seen as a grainy white region running down the left, and at right is the internal chamber of the heart.