The major cause of acute limb ischaemia is arterial thrombosis (85%), while embolic occlusion is responsible for 15% of cases. In rare instances, arterial aneurysm of the popliteal artery has been found to create a thrombosis or embolism resulting in ischaemia.

Risk factors for CRAO include the following: being between 60 and 65 years of age, being over the age of 40, male gender, hypertension, caucasian, smoking and diabetes mellitus. Additional risk factors include endocarditis, atrial myxoma, inflammatory diseases of the blood vessels, and predisposition to forming blood clots.

Thrombosis prevention is initiated with assessing the risk for its development. Some people have a higher risk of developing thrombosis and its possible development into thromboembolism. Some of these risk factors are related to inflammation. "Virchow's triad" has been suggested to describe the three factors necessary for the formation of thrombosis: stasis of blood, vessel wall injury, and altered blood coagulation. Some risk factors predispose for venous thrombosis while others increase the risk of arterial thrombosis.

70% of patients with carotid arterial dissection are between the ages of 35 and 50, with a mean age of 47 years.

The best course of treatment varies from case to case. The physician must take into account the details in the case before deciding on the appropriate treatment. No treatment is effective for every patient.

Treatment depends on many factors, including:

- Location of lesions

- Anatomy of lesions

- Patient risk factors

- Procedural risk

- Clinical presentation of symptoms

- Duration of symptoms

- etc.

Vascular occlusion is a blockage of a blood vessel, usually with a clot. It differs from thrombosis in that it can be used to describe any form of blockage, not just one formed by a clot. When it occurs in a major vein, it can, in some cases, cause deep vein thrombosis. The condition is also relatively common in the retina, and can cause partial or total loss of vision. An occlusion can often be diagnosed using Doppler sonography (a form of ultrasound).

Some medical procedures, such as embolisation, involve occluding a blood vessel to treat a particular condition. This can be to reduce pressure on aneurysms (weakened blood vessels) or to restrict a haemorrhage. It can also be used to reduce blood supply to tumours or growths in the body, and therefore restrict their development. Occlusion can be carried out using a ligature; by implanting small coils which stimulate the formation of clots; or, particularly in the case of cerebral aneurysms, by clipping.

The thrombi may dislodge and may travel anywhere in the circulatory system, where they may lead to pulmonary embolus, an acute arterial occlusion causing the oxygen and blood supply distal to the embolus to decrease suddenly. The degree and extent of symptoms depend on the size and location of the obstruction, the occurrence of clot fragmentation with embolism to smaller vessels, and the degree of peripheral arterial disease (PAD).

- Thromboembolism (blood clots)

- Embolism (foreign bodies in the circulation, e.g. amniotic fluid embolism)

Traumatic injury to an extremity may produce partial or total occlusion of a vessel from compression, shearing or laceration. Acute arterial occlusion may develop as a result of arterial dissection in the carotid artery or aorta or as a result of iatrogenic arterial injury (e.g., after angiography).

Risk factors include:

- Hypertension

- Elevated lipid levels

- cigarette smoking

- Diabetes

The main causes of thrombosis are given in Virchow's triad which lists thrombophilia, endothelial cell injury, and disturbed blood flow.

Causes include:

- Thrombosis (approximately 40% of cases)

- Arterial embolism (approximately 40%)

- arteriosclerosis obliterans

Another cause of limb infarction is "skeletal muscle infarction" as a rare complication of long standing, poorly controlled diabetes mellitus.

With treatment, approximately 80% of patients are alive (approx. 95% after surgery) and approximately 70% of infarcted limbs remain vital after 6 months.

The artery can re-canalize over time and the edema can clear. However, optic atrophy leads to permanent loss of vision. Irreversible damage to neural tissue occurs after only 90 minutes. Two thirds of patients experience 20/400 vision while only one in six will experience 20/40 vision or better.

Coronary vasospasm is a sudden, intense vasoconstriction of an epicardial coronary artery that causes occlusion (stoppage) or near-occlusion of the vessel.

It can cause Prinzmetal's angina.

It can occur in multiple vessels.

Atropine has been used to treat the condition.

The mean age of affected patients is 60 years. The right eye is affected more commonly than the left eye which probably reflects the greater possibility of cardiac or aortic emboli traveling to the right carotid artery.

Most of the cases are due to emboli to the retinal circulation. Three main types of retinal emboli have been identified: Cholesterol, calcific, and fibrin-platelet.

A coronary occlusion is the partial or complete obstruction of blood flow in a coronary artery. This condition may cause a heart attack.

In some patients coronary occlusion causes only mild pain, tightness or vague discomfort which may be ignored; however, the myocardium, the muscle tissue of the heart, may be damaged.

According to Robert K. Massie's "Nicholas and Alexandra: The Fall of the Romanov Dynasty", Tsar Nicholas II may have suffered a coronary occlusion right before he was toppled from his throne during the Russian Revolution in 1917.

The epidemiology of endothelial dysfunction is unknown, as %FMD varies with baseline artery diameter. This can make cross-sectional comparisons of %FMD difficult. Endothelial dysfunction was found in approximately half of women with chest pain, in the absence of overt blockages in large coronary arteries. This endothelial dysfunction cannot be predicted by typical risk factors for atherosclerosis (e.g., obesity, cholesterol, smoking) and hormones.

An embolism is the lodging of an embolus, a blockage-causing piece of material, inside a blood vessel. The embolus may be a blood clot (thrombus), a fat globule (fat embolism), a bubble of air or other gas (gas embolism), or foreign material. An embolism can cause partial or total blockage of blood flow in the affected vessel. Such a blockage (a vascular occlusion) may affect a part of the body distant from where the embolus originated. An embolism in which the embolus is a piece of thrombus is called a thromboembolism. Thrombosis, the process of thrombus formation, often leads to thromboembolism.

An embolism is usually a pathological event, i.e., accompanying illness or injury. Sometimes it is created intentionally for a therapeutic reason, such as to stop bleeding or to kill a cancerous tumor by stopping its blood supply. Such therapy is called embolization.

Once considered uncommon, spontaneous carotid artery dissection is an increasingly recognised cause of stroke that preferentially affects the middle-aged.

The incidence of spontaneous carotid artery dissection is low, and incidence rates for internal carotid artery dissection have been reported to be 2.6 to 2.9 per 100,000.

Observational studies and case reports published since the early 1980s show that patients with spontaneous internal carotid artery dissection may also have a history of stroke in their family and/or hereditary connective tissue disorders, such as Marfan syndrome, Ehlers-Danlos syndrome, autosomal dominant polycystic kidney disease, pseudoxanthoma elasticum, fibromuscular dysplasia, and osteogenesis imperfecta type I. IgG4-related disease involving the carotid artery has also been observed as a cause.

However, although an association with connective tissue disorders does exist, most people with spontaneous arterial dissections do not have associated connective tissue disorders. Also, the reports on the prevalence of hereditary connective tissue diseases in people with spontaneous dissections are highly variable, ranging from 0% to 0.6% in one study to 5% to 18% in another study.

Internal carotid artery dissection can also be associated with an elongated styloid process (known as Eagle syndrome when the elongated styloid process causes symptoms).

Arterial embolism can cause occlusion in any part of the body. It is a major cause of infarction, tissue death due to the blockage of blood supply.

An embolus lodging in the brain from either the heart or a carotid artery will most likely be the cause of a stroke due to ischemia.

An arterial embolus might originate in the heart (from a thrombus in the left atrium, following atrial fibrillation or be a septic embolus resulting from endocarditis). Emboli of cardiac origin are frequently encountered in clinical practice. Thrombus formation within the atrium occurs mainly in patients with mitral valve disease, and especially in those with mitral valve stenosis (narrowing), with atrial fibrillation (AF). In the absence of AF, pure mitral regurgitation has a low incidence of thromboembolism.

The risk of emboli forming in AF depends on other risk factors such as age, hypertension, diabetes, recent heart failure, or previous stroke.

Thrombus formation can also take place within the ventricles, and it occurs in approximately 30% of anterior-wall myocardial infarctions, compared with only 5% of inferior ones. Some other risk factors are poor ejection fraction (<35%), size of infarct, and the presence of AF. In the first three months after infarction, left-ventricle aneurysms have a 10% risk of emboli forming.

Patients with prosthetic valves also carry a significant increase in risk of thromboembolism. Risk varies, based on the valve type (bioprosthetic or mechanical); the position (mitral or aortic); and the presence of other factors such as AF, left-ventricular dysfunction, and previous emboli.

Emboli often have more serious consequences when they occur in the so-called "end circulation": areas of the body that have no redundant blood supply, such as the brain and heart.

Severe ipsilateral or bilateral carotid artery stenosis or occlusion is the most common cause of ocular ischemic syndrome. The syndrome has been associated with occlusion of the common carotid artery, internal carotid artery, and less frequently the external carotid artery. Other causes include:

- Takayasu's arteritis

- Giant cell arteritis

- Severe ophthalmic artery occlusion, due to thromboembolism.

- Surgical interruption of anterior ciliary blood vessels supplying the eye, particularly during extensive strabismus surgery on 3 or more rectus muscles, leading to an anterior segment ischemic syndrome.

In the first stage of restenosis, administering anti-platelet drugs (called IIb/IIIa inhibitors) immediately after surgery greatly reduces the chance of a thrombosis occurring.

Drug-eluting stents are now being trialled in Europe, Canada and the USA, as well as in Asia-Pacific. These stents are coated with pharmaceuticals that inhibit tissue growth and thus reduce the risk of restenosis from scar-tissue and cell proliferation.

There has been some success with these new stents in reducing the occurrence of restenosis, with clinical studies showing an incidence rate of 5% or lower.

In cardiac procedures, balloon angioplasty has been associated with a high incidence of restenosis, with rates ranging from 25% to 50%, and the majority of these patients need further angioplasty within 6 months.

A 2010 study in India comparing coronary drug-eluting stents (DES) with coronary bare-metal stents (BMS) reported that restenosis developed in 23.1% of DES patients vs 48.8% in BMS patients, and female sex was found to be a statistically significant risk factor for developing restenosis.

The prognosis depends on prompt diagnosis (less than 12–24 hours and before gangrene) and the underlying cause:

- venous thrombosis: 32% mortality

- arterial embolism: 54% mortality

- arterial thrombosis: 77% mortality

- non-occlusive ischemia: 73% mortality.

In the case of prompt diagnosis and therapy, acute mesenteric ischemia can be reversible.

Thrombotic Storm has been seen in individuals of all ages and races. The initial symptoms of TS present in a similar fashion to the symptoms experienced in deep vein thrombosis. Symptoms of a DVT may include pain, swelling and discoloration of the skin in the affected area. As with DVTs patients with TS may subsequently develop pulmonary emboli. Although the presentation of TS and DVTs are similar, TS typically progresses rapidly, with numerous clots occurring within a short period of time. After the formation of the initial clot a patient with TS typically begins a “clotting storm” with the development of multiple clots throughout the body. Rapid progression within a short period of time is often seen, affecting multiple organs systems. The location of the clot is often unusual or found in a spot in the body that is uncommon such as the dural sinus. Patients tend to respond very well to anticoagulation such as coumadin or low molecular weight heparin but may become symptomatic when treatment is withheld.

While the key clinical characteristics of thrombotic storm are still being investigated, it is believed that the clinical course is triggered by a preexisting condition, known as a hypercoagulable state. These can include such things as pregnancy, trauma or surgery. Hypercoagulable states can be an inherited or acquired risk factor that then serves as a trigger to initiate clot formation. However, in a subset of patient with TS a trigger cannot be identified. Typically people with TS will have no personal or family history of coagulations disorders.