Difference between embolism and a thrombosis?

Embolism and thrombosis are often confusing terms even for health professionals, and its definition, symptoms and consequences often overlap, since both conditions consist of a reduction or blockage of blood flow in the vascular lumen.


Thrombosis is the reduction of blood flow by the formation of a clot inside a blood vessel . The thrombus grows adhered to the vascular wall and as it grows it reduces the flow of blood through the vessel. The reduction of blood flow occurs at the site of thrombus formation.

The clot that produces thrombosis can be formed by very diverse causes, but atherosclerosis is by far the most frequent. Other causes are the increase in blood coagulation associated with various diseases and alterations of blood vessels that trigger the coagulation cascade, for example breaks and fissures in the vascular wall.

Thrombosis in a venous valve


The embolism, on the other hand, is the blocking of blood flow by any body, called a plunger , which moves until it finds a low-caliber vessel and blocks it . The obstruction does not occur in situ as in thrombosis, but at a distance. The plunger travels through the bloodstream until it finds a vessel through which it can not pass.

The emboli can be of different nature, including clots that detach from a thrombosis. That is, thrombosis reduces the blood flow in a vessel, and if a fragment is detached it forms a plunger that can cause an embolism.

The embolisms can have their causes in other types of materials, not only in blood clots , for example in fat globules, bubbles of air or gas and any other type of foreign body that enters the blood circulation. The blocked blood vessel can be a healthy vessel, unlike the thrombosis that develops in altered blood vessels.

Embolism by detachment of a clot

Common symptoms

Embolism and thrombosis share many symptoms and the risk to health depends primarily on the blood vessels that are affected, their location and the degree of blockage of blood flow, being the deep veins of lower extremities, large arteries, cerebral arteries, pulmonary blood vessels and coronary arteries that present a greater risk to the patient’s life.

The small thrombi and emboli do not usually block blood flow significantly, to the point that approximately 50% of cases of deep vein thrombosis, one of the most dangerous, do not develop symptoms. But larger obstructions can deprive healthy tissue of nutrients and oxygen, causing inflammation and eventually tissue death due to necrosis .

Venous and arterial thrombosis

Veins are the blood vessels responsible for bringing blood back to the heart for recirculation. When a main vein sees its flow reduced by a thrombosis, the blood behind the obstruction accumulates and undergoes extravasation producing edema, swelling and inflammation .

Although venous thrombosis can occur anywhere, deep vein thrombosis in the lower extremities is the most common. Thrombosis in superficial veins or small veins does not usually cause major complications.

For its part, arteries are the blood vessels that carry blood from the heart to different organs and tissues. Arterial thrombosis and embolisms are often associated with atheromatous plaques that grow, reducing vessel lumen and increasing pressure on the vascular wall. If the pressure becomes sufficient, it can break the plate and become unstable.

In this situation, the immune system overreacts and begins the formation of a large clot that hinders blood flow and can be life threatening by causing myocardial infarctions and strokes . The symptoms of arterial thrombosis that warn of this emergency situation usually include chest pain that does not remit with medication and that may appear suddenly, shortened breathing, sweating, nausea, loss of muscle strength and facial paralysis on one side.

Pulmonary embolism

Pulmonary embolism occurs when a plunger blocks blood flow to the lungs and is often associated with deep vein thrombosis . A fragment of the clot formed in the veins is detached and travels through the bloodstream, passing through the heart, until it reaches the pulmonary arteries.

Pulmonary embolism can be very dangerous and develop very quickly : sudden death is the first symptom detected in approximately 25% of pulmonary emboli. The most common symptoms that warn of a pulmonary embolism include shortness of breath, rapid breathing, increased heart rate , dizziness and lightheadedness, pain in the chest that intensifies when inhaling and coughing up blood.

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