Vascular occlusion is the blockage or closure of a blood vessel, which includes both arteries and veins. Arteries carry oxygen-rich blood from the heart to the rest of the body, while veins return that blood to the heart. When a vessel is occluded, this normal flow is interrupted, and the consequences depend on the vessel’s location, size, and the degree of the blockage. This condition can develop suddenly or gradually over time.
Causes of Vascular Blockages
A primary cause of arterial occlusion is atherosclerosis, a condition where fatty deposits, cholesterol, and other substances build up in artery walls to form plaque. This buildup narrows the arteries, restricting blood flow. Over time, these plaques can rupture, triggering the formation of a blood clot on their surface that can completely block the artery.
Another cause is the formation of blood clots, a process known as thrombosis. A thrombus is a blood clot that forms within a blood vessel and remains in place, impeding blood flow. In contrast, an embolism occurs when a piece of a blood clot (an embolus), plaque, or other material breaks free, travels through the bloodstream, and becomes lodged in a smaller vessel downstream.
Vascular occlusion can also result from direct physical trauma or external compression. An injury, such as a severe blow, can damage an artery or vein, leading to a blockage. Similarly, prolonged pressure on a part of the body can compress a blood vessel to the point of occlusion.
Finally, some occlusions are iatrogenic, meaning they are inadvertently caused by medical procedures. For instance, the injection of cosmetic dermal fillers can lead to vascular occlusion if the filler material is accidentally injected into a blood vessel. This can happen by direct injection or by the filler compressing an adjacent vessel, blocking blood flow.
Recognizing the Symptoms
The signs of a vascular occlusion depend on whether an artery or a vein is blocked and the location of the blockage. An acute arterial occlusion, a sudden blockage in an artery, is a medical emergency that produces immediate symptoms in the affected limb. These are often summarized as the “5 Ps”:
- Pain that is severe
- Pallor (a pale or whitish appearance of the skin)
- Pulselessness (the absence of a pulse below the blockage)
- Paresthesia (sensations of numbness or “pins and needles”)
- Paralysis or Poikilothermia (inability to move the limb and a cold feeling to the touch)
The pain associated with an acute arterial blockage is often intense and disproportionate to any physical findings. As the lack of oxygenated blood persists, the skin becomes cool and pale. The nerves begin to malfunction without their blood supply, leading to tingling and numbness, which can progress to a loss of sensation and motor function.
In contrast, symptoms of a venous occlusion, such as in deep vein thrombosis (DVT), tend to develop more gradually. A blocked vein prevents blood from returning to the heart, causing it to pool in the limb. This leads to symptoms like swelling, tenderness, and a feeling of warmth in the affected area. The skin over the blocked vein may also take on a reddish or bluish discoloration.
Diagnostic Procedures
To confirm a vascular occlusion, physicians use several diagnostic tools to visualize blood flow and pinpoint the blockage. A common initial test is the Doppler ultrasound, a non-invasive procedure that uses high-frequency sound waves to create images of blood vessels. This technique allows medical professionals to observe blood moving through arteries and veins, making it effective for identifying obstructions.
For a more detailed view, an angiography may be performed. In a Computed Tomography Angiography (CTA), a contrast dye is injected into the bloodstream, and a CT scanner takes a series of X-ray images. The dye makes the blood vessels visible, creating a detailed map showing narrowing or blockages. A catheter-based angiogram is more invasive, where a thin tube is guided through the blood vessels to inject dye directly, providing very precise images.
In addition to imaging, certain blood tests can aid in diagnosis. A D-dimer test measures a substance that is released when a blood clot dissolves. Elevated levels of D-dimer in the blood can suggest the presence of a thrombus somewhere in the body, although it does not specify the location. This test is often used when a venous occlusion like DVT is suspected.
Medical Interventions and Treatments
Once a vascular occlusion is diagnosed, treatment focuses on promptly restoring blood flow. The approach depends on the location, severity, and cause of the blockage. Medications are often a first line of defense. Anticoagulants, known as blood thinners, such as heparin and warfarin, prevent new clots from forming and stop existing clots from growing.
In situations with severe arterial blockages, more powerful drugs called thrombolytics may be used. These “clot-busting” medications can dissolve existing clots to quickly restore blood flow. They are often administered directly to the site of the clot through a catheter in a procedure called catheter-directed thrombolysis.
Minimally invasive procedures are frequently used to physically open blocked vessels. During an angioplasty, a catheter with a small balloon at its tip is guided to the blockage and inflated to compress the plaque and widen the artery. A small, expandable mesh tube called a stent is often placed within the artery during angioplasty to help keep it open.
For extensive or hard-to-reach blockages, surgical intervention may be necessary. A thrombectomy is a surgical procedure to directly remove a blood clot from a vessel. In cases of severe atherosclerosis where a significant portion of an artery is blocked, bypass surgery might be performed. This operation creates a new route for blood flow by grafting a blood vessel to go around the occluded section.