Arterial Thrombosis (Blood Clot in an Artery)

How arterial thrombosis happens

Over years, cholesterol, inflammatory cells and scar tissue build up in artery walls as plaques (atherosclerosis). When a plaque cracks or erodes, its contents are exposed to blood. Platelets stick to the site and trigger clotting, forming a thrombus. It may partly narrow the artery, causing intermittent symptoms, or block it completely.

Clots can also form elsewhere and travel into an artery (embolism). The most common source is the heart in atrial fibrillation, where blood pools in the upper chambers.

Arterial vs venous thrombosis

See deep vein thrombosis for clots in veins.

Symptoms by location

• Heart (coronary arteries): chest pain or pressure, pain in the arm, jaw or back, breathlessness, sweating and nausea. This is a heart attack.
• Brain: sudden weakness or numbness on one side, facial droop, trouble speaking, vision loss or loss of balance. This is an ischemic stroke.
• Legs or arms: the "6 Ps": pain, pallor (pale), pulselessness, paresthesia (pins and needles), paralysis and poikilothermia (cold). This is acute limb ischemia.
• Bowel (mesenteric ischemia): sudden severe belly pain, often worse than the examination suggests.
• Kidneys: flank pain and blood in the urine.
• Eye: sudden painless loss of vision in one eye (retinal artery occlusion).

Causes and risk factors

• smoking
• high blood pressure
• high LDL cholesterol
• diabetes
• obesity and physical inactivity
• older age and male sex
• family history of early heart disease
• chronic kidney disease
• atrial fibrillation and other heart conditions (for emboli)
• antiphospholipid syndrome and some blood cancers that increase clotting
• cocaine and amphetamine use
• inflammation of arteries (vasculitis) and artery injury

Diagnosis

• Heart: ECG, blood troponin and coronary angiography.
• Brain: CT or MRI scans, often with CT angiography.
• Limbs: examination of pulses, Doppler ultrasound and CT or catheter angiography.
• Source checks: ECG monitoring for atrial fibrillation, echocardiogram, and blood tests for clotting disorders in young people or unusual cases.

Treatment

Treatment must be fast, because tissue begins to die within minutes to hours.

• Heart attack: urgent coronary angioplasty and stenting, or clot-busting medicine if a catheter lab is not available quickly, plus antiplatelets and anticoagulants.
• Stroke: IV thrombolysis within 4.5 hours of onset for suitable patients, and mechanical thrombectomy for large artery blockages, often up to 24 hours in selected cases.
• Acute limb ischemia: IV heparin, then catheter-directed thrombolysis, clot removal, angioplasty or bypass surgery.
• Mesenteric ischemia: emergency revascularization and removal of dead bowel.

Long-term treatment

• Antiplatelet medicines (aspirin, clopidogrel, ticagrelor) to prevent new clots on plaques.
• Anticoagulants when the clot came from the heart, such as in atrial fibrillation. See anticoagulant therapy.
• High-intensity statins to lower cholesterol and stabilize plaques.
• Blood pressure and diabetes control.
• Cardiac or stroke rehabilitation and supervised exercise for peripheral artery disease.

Prevention

• Do not smoke, and avoid secondhand smoke.
• Keep blood pressure below the target your doctor sets, often below 130/80 mm Hg.
• Lower LDL cholesterol with diet and statins as advised.
• Manage diabetes and weight.
• Aim for at least 150 minutes of moderate exercise a week.
• Take prescribed antiplatelets or anticoagulants consistently.

Frequently asked questions

What are the symptoms of a blood clot in an artery?

Symptoms depend on which artery is blocked: chest pain in a heart attack, sudden weakness, numbness or speech problems in a stroke, and a cold, pale, painful, numb limb in limb ischemia. These appear suddenly and need emergency care.

What is the difference between arterial and venous thrombosis?

Arterial clots form in arteries, usually on cholesterol plaques, and cause heart attacks, strokes and limb ischemia. Venous clots form in veins, usually from slow blood flow, and cause DVT and pulmonary embolism. They are prevented with different medicines.

How is arterial thrombosis treated?

Emergency treatment restores blood flow using clot-dissolving drugs, catheter-based clot removal, angioplasty and stents, or bypass surgery. Afterward, antiplatelet medicines, statins and control of blood pressure, diabetes and smoking prevent further clots.

Can arterial thrombosis be prevented?

Many cases can. Not smoking, controlling blood pressure, cholesterol and diabetes, staying active, and taking prescribed antiplatelet or anticoagulant medicines greatly reduce the risk of heart attack, stroke and limb clots.