An infarct is a limited area of necrosis caused by interruption of arterial blood flow to a specific tissue. The most common causes of this disorder are atherosclerosis, thrombosis and blood vessel embolism. The development of a heart attack is a complex and unpredictable process, and whether necrosis will occur and how intense it will be depends on: the degree of tissue differentiation, the speed of blood vessel obstruction, the type of circulation in the affected area and the degree of tissue functional activity. Risk factors include decompensated heart defects, anemia, etc.
The size of the infarct depends on the size of the blocked blood vessel and ranges from a few millimeters to tens of centimeters (eg brain and lungs).
Its shape is different and depends on the architecture of the arterial circulation. On the cross-section of the lung, kidney or spleen, it has the shape of a cup, the base of which is turned towards the periphery of the organ, and the top towards its interior (hilus). A brain infarction usually has the shape of an irregular ball, in the kidneys it can also have a trapezoid and deltoid shape, a heart muscle infarction is plate-shaped, etc.
In relation to the surrounding tissue, which is well supplied with blood, the necrotic area is clearly limited. This border is mostly straight, while in myocardial infarction it is jagged.
The consistency of the infarction depends on the type of necrosis and the structure of the organ itself. Initially, it is usually firmer than the surrounding unchanged tissue (coagulation type of necrosis), although the infarct of an organ with a high content of water and fat has a soft consistency from the beginning (collivation type of necrosis).
As for the color, it is different: white infarct (in organs with terminal type of circulation), red infarct (in organs with collateral type of circulation) and white infarct with a red border (in heart muscle and kidney).
At the macroscopic level, no changes are observed in the first few hours from the moment of blockage of the blood vessel. Then the necrotic tissue becomes firmer and paler in the case of an anemic infarction, or redder in the case of a hemorrhagic infarction. After 24 hours, softening of the affected area begins and it reaches its maximum after 3-4 days. In the following period, the tissue takes on a red-greyish, and then a grayish-reddish color, due to the proliferation of young granulation tissue.