Thromboembolic Complications

What pathophysiological factors are included in the classic Virchow's triad?

The classic Virchow's triad includes three main pathophysiological factors contributing to thrombosis.

• Vascular wall injury — disruption of endothelial integrity due to trauma, infections, or other causes.
• Blood flow disruption — slowing of blood flow, venous stasis, or stagnation.
• Hypercoagulation — activation of coagulation hemostasis, increased blood clotting ability, and suppression of fibrinolysis.

What is the mechanism of the anticoagulant action of heparin sodium?

The mechanism of the anticoagulant action of heparin sodium is based on interaction with endogenous antithrombin III.

• Binding — heparin attaches to the antithrombin III molecule.
• Conformational change — the spatial structure of antithrombin III changes, which dramatically increases its affinity for serine proteases (blood clotting enzymes).
• Complex formation — the protease attaches to the complex, forming an inactive compound.
• Recirculation — after the protease binds, heparin is released and can activate new antithrombin III molecules.

What are the absolute contraindications to prescribing anticoagulant therapy?

Absolute contraindications to prescribing oral anticoagulants include:

• Hemoglobin drop below 80 g/L of unclear origin.
• Recurrent intracranial hemorrhage.
• Intracranial mass.
• End-stage liver disease — Child-Pugh class C hepatic impairment; this is a contraindication for DOACs, and warfarin is not indicated if the baseline INR is above the therapeutic range.

What clinical symptoms are characteristic of the development of pulmonary embolism (PE)?

Clinical manifestations of PE may include:

• Massive PE — acute cardiopulmonary failure syndrome, chest pain, sudden loss of consciousness.
• Less severe cases, segmental artery embolism — nonspecific symptoms: retrosternal pain, cough, tachypnea.
• Symptoms of possible PE — dyspnea, cough, hemoptysis, brief loss of consciousness (syncope), tachycardia.

The sensitivity and specificity of these symptoms are most likely low; one or more symptoms may be caused by other conditions unrelated to DVT or PE.

What instrumental methods are the standard for diagnosing deep vein thrombosis?

For the instrumental diagnosis of deep vein thrombosis, the following are used:

• Ultrasound of the lower extremity veins — the terms ultrasound angioscanning and duplex/triplex scanning imply performing compression angioscanning, as well as duplex and/or triplex scanning. The highest diagnostic value is indicated for B-mode examination with vein compression every 2 cm.
• Phlebography — provides the most complete information on the state of venous blood flow and deep veins.

What surgical interventions are used to prevent PE in the presence of free-floating (flailing) thrombi?

To prevent massive PE in patients with DVT, the following are used:

• Endovascular methods — vena cava filter implantation, catheter thrombectomy.
• Open surgical methods — thrombectomy, ligation of the deep vein proximal to the thrombus, plication of the inferior vena cava.

If a thrombus in the femoropopliteal segment is detected and vena cava filter implantation is impossible, ligation or plication of the superficial femoral vein with a absorbable ligature may be considered.