Thrombotic Occlusion - Types, Symptoms, Risk Factors, Diagnosis, and Treatment

Introduction

Complete blockage or partial narrowing of a blood vessel (artery or vein) leading to reduced blood flow is termed occlusion. Occlusion in vascular vessels occurs due to various reasons such as an internal obstruction (clot formation or tumor growth), a foreign body (filler material used in cosmetic injections), and external compression (application of tourniquet during surgery). Management of blood vessel occlusions is an emergency situation because not treating them appropriately results in tissue necrosis and cell death. This article focuses on occlusions due to clot formation, its causes, diagnosis, and treatment.

What Is Thrombotic Occlusion?

Thrombus is a fibrin blood clot that is usually formed at the site of injury to stop bleeding as a hemostatic mechanism. When this thrombus is formed inside the blood vessels (intravascularly), it obstructs normal blood circulation resulting in thrombotic occlusions. These occlusions could be complete (the entire lumen of the blood vessel is blocked) or partial (the width of the lumen is reduced). Based on the site of formation, thrombotic occlusions are classified as,

• Arterial thrombotic occlusions.

• Venous thrombotic occlusion.

• Device-induced thrombotic occlusion.

Arterial Thrombotic Occlusion

Thrombus formation inside the artery leads to arterial occlusion. Since arteries carry oxygen and nutrient-rich blood from the heart to the body tissues, disruption in arterial blood flow causes tissue hypoxia (lack of oxygen supply) and cell damage. The causes and risk factors for arterial thrombotic occlusions include;

• Atherosclerosis (deposition of fatty plaque on the arterial walls).

• Embolism (dislodged blood clot from the site of formation).

• Turbulent blood flow and shear forces exerted on the walls.

• Atrial fibrillation.

• Smoking.

• Comorbid conditions like hypertension, diabetes, and high cholesterol.

• Lack of physical activity.

• Aging (thickening of muscles in the arteries).

• Alcohol consumption.

• Obesity.

• Unhealthy food habits.

• Genetic predisposition (family history of atherosclerosis).

Venous Thrombotic Occlusion

Blood clot inside a vein causes venous thrombotic occlusion. Veins are draining blood vessels that carry deoxygenated blood and metabolic wastes produced in the tissues of the heart. Here occlusions occur due to blood clots as well as tumor growth, injection of foreign bodies, or air bubbles. The predominant causes and risk factors for venous thrombotic occlusions include;

• Fracture or muscle injury.

• Pulmonary embolism (one or more arteries of the lungs blocked by a blood clot).

• Deep vein thrombosis (DVT).

• Embolization (use of coagulants to treat hemorrhage) of varicose veins.

• Prolonged hospitalization and restricted movement.

• Paralysis.

• Hormone replacement therapy.

• Oral contraceptive pills.

• Obesity.

• Smoking.

• Hereditary clotting disorders.

• Chronic medical illnesses.

• Cancer.

• Aging and pregnancy.

• Dehydration.

Device-Induced Thrombotic Occlusions

Thrombotic occlusions also occur due to the formation of a fibrin clot around or inside the tip of the catheter. All catheters accumulate fibrin initially when introduced inside the body since it is considered a foreign material. It is dissolved by the use of anticoagulants. But any infection, increased duration, or malfunction results in thrombotic occlusions of the catheters. Some of them include;

• Long-term central venous catheters.

• Infection and sepsis.

• Parenteral drug administration.

• Mechanical obstruction due to subcutaneous fat or malpositioning of the catheter.

• Common in children receiving cancer chemotherapy.

What Are the Signs and Symptoms of Thrombotic Occlusions?

Blood clots frequently result in medical emergencies with severe signs and symptoms that are often fatal. The clinical manifestations of thrombotic occlusions vary according to the severity of the narrowing and the type of vessel involved. They are,

• Coronary artery occlusions cause ischemia, chest pain, heart attack, and myocardial infarction.

• Chest pain, nausea, vomiting, headache.

• Obstruction in the carotid trunk obstructs blood to brain tissue resulting in stroke or paralysis of the facial muscles, slurred speech, and disorientation.

• Central artery occlusion leads to optic atrophy and blindness.

• Occlusions in the peripheral arteries cause pain, altered sensation in the skin, and paraesthesia in the affected limb.

• Swollen legs with cramping muscle pain in case of deep vein thrombosis.

• Septic shock in catheter infections,

How Are Thrombotic Occlusions Diagnosed?

Diagnosis of thrombotic occlusions requires swiftness to avoid morbid consequences and is immediately picked out by imaging techniques.

• Ultrasound Scan - Sound waves with high frequency are used to monitor closed body parts. The echos from blood clots differ from that of patent blood vessels and produce images of thrombotic occlusion.

• Venography - In case of deep vein thrombosis, a special radio-opaque dye is injected into the veins and an X-ray is taken. The flow of dye is prevented by occlusions and is detected in the blocked veins as radio opacities.

• Angiogram - To identify a block in coronary arteries,it is an imaging technique to navigate inside the arterial lumen and detect the block using contrast dye.

• Fluoroscopy - To detect a block in the retinal artery,fluorescent dyes are used and with the help of X-ray, live images of blood flow are assessed.

• Doppler Study- An advanced form of ultrasound where sound waves (high-frequency) that are bouncing from the circulating blood cells help in estimating the intensity of blood flow in a vessel.

• Radiography and Linogram - Linogram is the X-ray of the central venous catheter to detect occlusion in the tip of the catheter.

What Are the Treatment Interventions for Thrombotic Occlusions?

Thrombotic occlusions are treated by both surgeries and medications depending on the damage caused due to reduced blood supply.

• Injection of thrombolytic agents like heparin, and warfarin at the site of thrombus formation.

• Embolectomy (surgical removal of blood clot).

• Angioplasty (hollow tube introduced into the arterial lumen to keep the tube patent).

• Bypass grafts and stents (done in coronary artery blockage to divert blood flow).

• Intraluminal thrombolytic agents are administered in case of catheter-associated occlusions.

• Repositioning of catheters, reviewing dosage of parenteral administration of medications, and use of sodium hydroxide or sodium bicarbonate or ethanol 70 % to wash away fibrin clots around catheters.

• New thrombolytic medications like Reteplase are used in the management of catheter-induced occlusions because of their higher potential efficacy and lower dwell duration.

• Use of long-term central venous catheters follows standard protocols on the methods and frequency of flushing the catheters to prevent catheter-associated occlusions. 10 U/mL (units per milliliter) heparin, 100 U/mL heparin and normal saline are commonly used for flushing catheters.

How to Reduce the Risk of Thrombotic Occlusions?

Thrombotic occlusions could be prevented or reduced by lowering the causes of risk factors that result in thrombosis.

• Lowering the risk of atherosclerosis by lifestyle modifications.

• A balanced and healthy diet with minimal fat content.

• Regular physical activity.

• Reducing overweight and obesity.

• Stopping alcohol consumption.

• Medications (statins) to lower cholesterol levels in the blood.

• Regular monitoring of comorbid conditions like diabetes and hypertension.

• Use of oral anticoagulants (low-dose Aspirin warfarin, vitamin K antagonists) in individuals with a higher risk for thrombosis under medical consultation.

• Regular walking and keeping the affected leg elevated during rest (in case of deep vein thrombosis).

• Maintain a healthy weight and avoid prolonged sitting.

• A lot of fluid intake to avoid dehydration.

• Use of compression stockings (knee-high socks made of elastic material to blood circulation) in individuals prone to deep vein thrombosis.

• Low-dose heparins are recommended for individuals with long-term central venous catheters.

Conclusion

Thrombotic occlusions are life-threatening conditions that require emergency intervention protocols. Though associated with severe morbidities early detection and management would prevent fatal consequences. Avoiding risk factors and adopting healthy lifestyle modifications would dramatically reduce the complications of thrombotic occlusions.