This table gives an overview of the pathology

Pathology

Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....

 seen in myocardial infarction

Myocardial infarction

Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

by time after obstruction.

For the first ~30 minutes no change at all can be seen by gross examination

Gross examination

Gross examination or "grossing" is the process by which pathology specimens are inspected with the bare eye to obtain diagnostic information, while being processed for further microscopic examination....

 or by light microscopy in histopathology

Histopathology

Histopathology refers to the microscopic examination of tissue in order to study the manifestations of disease...

. However, in electron microscopy relaxed myofibrils, as well as glycogen loss and mitochondrial swelling can be seen.

Time	Gross examination Gross examination Gross examination or "grossing" is the process by which pathology specimens are inspected with the bare eye to obtain diagnostic information, while being processed for further microscopic examination....	Histopathology Histopathology Histopathology refers to the microscopic examination of tissue in order to study the manifestations of disease...   (light microscopy)
0 - 0.5 hours	None	None
0.5 - 4 hours	None	Glycogen Depletion, as seen with a PAS Stain Possibly waviness of fibers at border
4 - 12 hours	Sometimes dark mottling Mottle Mottle or mottling is the appearance of uneven spots. It is commonly used to describe plants or the skin of animals. In plants, mottling usually consists of yellowish spots on plants, and is usually a sign of disease or malnutrition...	Initiation of coagulation necrosis Edema Edema Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling... Hemorrhage
12 - 24 hours	Dark mottling	Ongoing coagulation necrosis Karyopyknosis Hypereosinophilia Hypereosinophilia Hypereosinophilia is a disease characterised by a marked increase in the eosinophil count in the bloodstream.The eosinophil count in human blood is normally 0.4 × 109/L and results from a balance between production of eosinophils and emigration through post-capillary venules...  of myocytes Contraction band necrosis Contraction band necrosis Contraction band necrosis is a type of uncontrolled cell death unique to cardiac myocytes and thought to arise in reperfusion from hypercontraction, which results in sarcolemmal rupture....  in margins Beginning of neutrophil infiltration
1 - 3 days	Infarct center becomes yellow-tan Tan (color) Tan is a pale whiteish, tawny shade of white. The name is derived from tannum used in the tanning of leather.The first recorded use of tan as a shade name in English was in the year 1590....	Continued coagulation necrosis Loss of nuclei and striations Increased infiltration of neutrophils to interstitium Interstitial fluid Interstitial fluid is a solution that bathes and surrounds the cells of multicellular animals. It is the main component of the extracellular fluid, which also includes plasma and transcellular fluid...
3 - 7 days	Hyperemia at border Softening yellow-tan center	Beginning of disintegration of dead muscle fibers Necrosis of neutrophils Beginning of macrophage Macrophage Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...  removal of dead cells at border
7 - 10 days	Maximally soft and yellow-tan Red-tan margins	Increased phagocytosis of dead cells at border Beginning of granulation tissue Granulation tissue Granulation tissue is the perfused, fibrous connective tissue that replaces a fibrin clot in healing wounds. Granulation tissue typically grows from the base of a wound and is able to fill wounds of almost any size it heals...  formation at margins
10 - 34 days	Red-gray and depressed borders	Mature granulation tissue with type I collagen
2 - 8 weeks	Gray-white granulation tissue	Increased collagen deposition Decreased cellularity
More than 2 months	Completed scarring	Dense collagenous scar formed
If not else specified in boxes, then reference is nr

Once scarring is completed, there is yet no common method of telling the actual age of the infarct, since e.g. a scar that is four months old looks identical to a scar that is ten years old.