Makindo Medical Notes

Related Subjects: | Pulmonary Embolism | Deep Vein Thrombosis | DVT/PE in Pregnancy | CTPA

The subclavian vein is located beneath the clavicle and continues from the axillary vein. It merges with the internal jugular vein to form the brachiocephalic vein.

About

• Subclavian vein thrombosis (SCVT) is an upper-extremity deep vein thrombosis (DVT).
• It has multiple causes, ranging from trauma to underlying medical conditions.

Aetiology (Virchow’s Triad)

• Changes in blood composition (e.g., hypercoagulability)
• Changes in blood flow (e.g., stasis or turbulence)
• Changes in the vessel wall (e.g., endothelial damage)

Causes

• Primary SCVT (Effort-Induced Thrombosis):
  • Paget-Schroetter Syndrome: Affects young, healthy individuals, typically following vigorous physical activity.
  • Idiopathic: Often associated with undiagnosed malignancies.
• Secondary SCVT:
  • Mechanical Trauma: Compression of the subclavian vein (e.g., clavicle fracture).
  • Chronic Central Venous Catheters (CVCs) or Pacemaker Leads: These devices can cause trauma and lead to thrombosis.
  • Hemodialysis Catheters or Long-Term TPN Feeds: Prolonged use of intravascular devices can damage the vein walls.
  • Prone Positioning during Surgery: This can increase the risk of vein compression.
  • Inherited Thrombophilia: Conditions such as Antithrombin III deficiency, Factor V Leiden mutation, and Protein C/S deficiency.
  • Lung Cancer: Particularly Pancoast tumours, which can compress or invade the subclavian vein.

Clinical Features

• Swelling, Oedema, and dilated veins in the upper limb.
• Heaviness or discomfort in the arm, with possible lymphadenopathy (cervical and axillary).
• Visible distension of superficial veins in the neck, shoulder, or arm.
• Cyanosis (bluish skin discoloration) in the hand or fingers.
• Breast examination may be indicated if malignancy is suspected.

Investigations

• FBC, U&E, ESR/CRP, and elevated D-dimer.
• Thrombophilia screening in select patients, especially younger individuals.
• CXR, CT, or MRI venography to visualize the thrombosis.
• Ultrasound of the upper limb veins to detect the clot and assess blood flow.
• Contrast venography is the gold standard but is more invasive.
• Mammography may be considered if breast malignancy is suspected.

Complications

• Pulmonary Embolism (PE)
• Post-thrombotic syndrome: Venous outflow obstruction and valvular insufficiency, which can range from mild edema to severe venous stasis and ulcer formation.
• Septic thrombophlebitis
• Superior vena cava syndrome (due to large thromboses).
• Loss of access due to catheter occlusion (in cases involving CVCs).

Differential Diagnoses

• Superior vena cava syndrome
• Lymphatic obstruction
• Cellulitis
• Thoracic outlet obstruction
• Pancoast tumour
• Necrotizing fasciitis
• Superficial thrombophlebitis

Management depends on the underlying cause

• Thrombolysis: In catheter-related or effort-induced SCVT, catheter-based thrombolysis may be considered.
• Stenting: May be an option if there is significant narrowing of the vein.
• Anticoagulation: Start with low molecular weight heparin (LMWH), followed by warfarin or direct oral anticoagulants (DOACs).
• Underlying Causes: Investigate for potential underlying malignancy or thrombophilia, especially in patients under 45 or with a family history of venous thromboembolism (VTE).
• Central Venous Catheter Removal: If a catheter is the cause of the thrombosis, removal may be necessary after the acute phase is managed.

References

• Subclavian Vein Thrombosis