Infarction is defined as the obstruction of a local blood supply which results in a lack of oxygen (ischemia) and possibly the death of the local tissue.
Infarction might be classified according to its location. 8 main types of infarctions are distinguished:
As for etiology, the diagnosis of infarction depends on the type concerned. Let us consider yet again the cases of myocardial and cerebral infarction, the most frequent and widespread among patients:
There are two main interventions used to remove a blockage in the blood vessels causing an episode of infarction: breaking down the blood clot using an appropriate drug or removing the clot mechanically. The more rapidly the clot is removed and the flow is restored, the lower the final level of damage.
A classic example of intervention aimed at mechanically removing the blood clot responsible for the episode of infarction is percutaneous coronary intervention, commonly known as coronary angioplasty, used to treat the coronary arteries in coronary heart disease. The operation is often performed by inserting a deflated balloon on a catheter in the femoral artery and push it through the blood vessels until it reaches the site of blockage. Once reached the blockage, the balloon is then inflated to re-open the artery and a stent may be placed there to hold open the blood vessel and prevent re-narrowing. The stent stays in place permanently as the blood vessel lining heals over it. While performing the delicate intervention, the clinician uses X-ray imaging to guide the movements of the catheter. In other types of infarction, like cerebral infarction, the clinician can also use a corkscrew-like device to ensnare the blood clot, which is then withdrawn from the body while removing the catheter.
The blood clot can also be chemically dissolved by using thrombolytic drugs. These agents mostly work by activating the enzyme plasminogen, famous for degrading many blood plasma proteins including fibrin clots. The plasmonigen so activated clears the cross-linked fibrin mesh (the core of the clot) which in turns becomes soluble and subject to further proteolysis by other enzymes, until it is completely dissolved and the blood flow is entirely restored.
The short term prognosis of infarction might be very poor involving the perennial damage of the local tissue, if the problem is not promptly treated. On the long run, survival rate has increased dramatically over the last two decades. In fact, the prognosis is very good for most people that reach the hospital soon after the appearance of the symptoms. However, the cases of subjects experiencing sudden death, that do not even make it to the hospital, still remains relatively frequent. Therefore, prevention is paramount to effectively treat infarction and its long and short term side effects.
The other most common causes of infarction include thrombosis and embolism in the artery nearby the site of the infarction itself. Thrombosis is defined as the formation of a blood clot which obstructs the blood flow, and this usually occurs when a vessel is injured. In fact, after an injury the platelets and fibrin form a clot to prevent blood loss. This clot might break free and begin to travel as a solid mass which blocks local blood vessels (especially small sized ones like capillaries). The floating mass might be gaseous or liquid in nature and is called embolus  and its formation embolism. An embolus generally goes away from the site of formation to reach distant sites. In both case, this occlusion of local blood vessels provokes a decreased blood supply which eventually results in infarction and the death of the local tissue.
Other less common causes of infarction include:
Furthermore, infarction should not be confused with congestion. In fact, congestion usually occurs when veins are occluded. An occluded vein always results in ischemia, but the common outcome of this condition is the formation of some bypass channels which helps the blood flood and improves vein drainage with the blood moving away from the site of congestion. However, sometime infarction might result from congestion, and this happens when congestion occurs in those organs with a single efferent vein such as ovaries. Thus, the only outcome possible for the blockage of that single efferent vein is inevitably infarction.
The etiology of infarction depends on the type taken into consideration. Let us consider the most important types, myocardial infarction and cerebral infarction:
The pathophysiology of the most common type of infarction, the type due to the formation of an atherosclerotic plaque, is described here. In this case the blood flow is blocked, and this causes the damage of the tissue nearby because, as previously said, it no longer gets an adequate amount of oxygen from the blood. In the case of a myocardial infarction, the blockage affects usually the coronary arteries, even though occlusions and spasms are also frequent enough. The inside of the blood vessel narrows and hardens, because of the buildup of the plaque of fatty material, and the blood flood to the heart muscles is decreased. If the plaque cracks or breaks open, a blood clot forms on the surface of the plaque itself, and the latter, also called thrombus, completely blocks the blood flow in the artery. Once the blood flow is blocked, infarction takes place, as a part of the surrounding tissue becomes damaged. In the case of myocardial infarction, the damage of the heart muscles that might finally result in the impaired activity of the heart, which can no longer pump blood into the body in a proper manner, if not completely becoming unable to do so. If the block is not promptly removed, the damaged tissue will begin to die and be replaced by scar tissue. It is important to remember that this damage might not be obvious and might cause severe and long-lasting symptoms.
Prevention is mainly based on avoiding the formation of a build-up of fatty materials in the blood vessels, which is the primary cause of all types of infarction. This can be achieved through a series of important changes in lifestyle, like stopping the use of tobacco, performing physical exercise on a daily basis (at least 30 minutes a day, five times a week), following an healthy die, and avoiding stress.
The key event underlying infarction is the block of the local blood supply which comes as consequence of different circumstances. For example, the obstruction might be caused by the presence of a block which prevents the blood from flowing, like an embolus (gaseous or liquid mass), a thrombus (a compact mass of other blood elements) or an atherosclerotic plaque, or it might be caused by a mechanical compression (tumor or hernia), a trauma or a vasoconstriction.
The most frequent of these causes is undoubtedly the development of an atherosclerotic plaque, in other words the accumulation of degenerative material in the tunica intima which mainly consists of macrophage cells  , debris, lipids, calcium and fibrous connective tissue. Eventually, the plaque is degraded by metalloproteinases or by the sheer force of the blood flow, and the subendothelial thrombogenic material, that is the collection of extracellular molecules providing structural and biochemical support to surrounding cells , is exposed to circulating platelets and provokes thrombus formation.
Infarction is defined as the obstruction of a local blood supply which results in a lack of oxygen (ischemia) and possibly the death of the local tissue. The main causes of infarction include the formation on an embolus (a gaseous or liquid mass), a thrombus (a compact mass of blood elements), and an atherosclerotic plaque. Other possible but less common causes include vessel spasm, compression by a nearby tumor, artery torsion, and vessel rupture.
Infarction is usually classified according to the site of the blockage. The main ones include: heart infarction, cerebral infarction, and pulmonary infarction. The treatment of this pathological condition basically involves the mechanical removal of the blockage or its chemical dissolution through thrombolytic drugs. Since the formation of the blockage is a long term event, largely based on an unhealthy lifestyle, prevention is paramount and include changes like stopping the use of tobacco, performing physical exercise, following an healthy diet, and avoiding stress.