Upper limb ischaemia Flashcards
What percentage of limb ischaemia occurs in the upper limb
5%
Embolic occlusion is responsible for 90% of acute upper limb ischaemia, what is usually the source of the emboli?
- The heart (70% of upper limb emboli): atrial fibrillation, mural thrombus, valvular lesions or ventricular aneurysm
- Other sources: Atherosclerotic plaque from aortic arch or proximal large vessels and aneurysms in the proximal vessels
Embolic occlusion at which level leads to limb threatening ischaemia?
Embolic occlusion of the brachial artery proximal to the origin of the arteria profunda brachii leads to limb threatening ischaemia due to insufficient collaterals
What are the causes of acute in situ thrombosis
- secondary to atherosclerosis in larger proximal vessels, thrombosis of proximal vessel aneurysm or secondary to arterial thoracic outlet compression
Important iatrogenic causes of penetrating injury to the arteries
- Invasive monitoring (intra-arterial lines)
- Diagnostic procedures (arteriograms)
- Therapeutic procedures (percutaneous transluminal angioplasty and stenting)
Examples of pathology in the aortic arch causing acute occlusion of the origin of the arch vessels (brachiocephalic and left carotid and subclavian arteries)
Takayasu’s arteritis and acute dissection
Examples of hypercoaguable states causing acute thrombosis
- Deficiency of anti-thrombin
- Deficiency of protein C and S
- Presence of antiphospholipid syndrome
- Paraneoplastic hypercoaguability
Clinical features of acute upper limb ischaemia
- Sudden onset pain, pallor, poikilonthermia, paraesthesia and paralysis
- On examination: Peripheral pulses absent, limb cold and pale
- As ischaemic time progresses, the skin may appear mottled which initially blanches on digital pressure
Signs of irreversible ischaemia and unsalvageable limb?
Fixed blue staining of the skin and tense, tender muscle compartments
Conditions causing acute digital ischaemia
- Embolism
- Vasospasm
- Vibration trauma
- Hypotermic injury
- ergotism
- Intra-arterial injections
- Trauma
- iatrogenic injury
- Fibromuscular dysplasia
- Radiation arteritis
- Congenital arteriopathies: Ehlers-Danlos, marfan
- Behcet syndromes
Treatment of acute upper limb ischaemia
- Immediate anticoagulation with 70 - 100 units of unfractionated heparin/ kg body weight given intravenously
- Appropriate analgesia
- Referred to specialist vascular unit
- Embolectomy can be performed under local anaesthesia
How is an embolectomy performed for emboli lodged at the site of the brachial bifurcation
- S-shaped incision in ante-cubital fossa
- Brachial artery exposed
- Transverse arteriotomy made
- Embolus is retrieved by passing embolectomy catheter distally into the forearm vessels and proximally into the brachial artery
- Proximal patency confirmed
- Distal vessels flushed with heparin-saline solution and arteriotomy closed with 7/0 interrupted sutures
How should patients who present with acute on chronic occlusion be treated?
- Catheter-directed intra-thrombus administration of a thrombolytic agent is of value for dissolution of thrombus to identify underlying lesions.
- Final treatment depends on the nature and location of the pathology
management of acute ischaemia due to inadvertent intra-arterial injections
- When diagnosis is made with needle in situ, irrigate with a heparin-saline solution for dilution and anti-coagulant effect
- Injection of a vasodilator (nitroglycerine/papaverine/ lignocaine)
- Patient fully anticoagulated with unfractionated heparin
- Low molecular weight dextran given as continuous infusion together with dexamethosone
- Prostacyclin may be given
- Appropriate analgesia
- Brachial plexus block may be of value
- Arterial bypass and fasciotomy is indicated with large vessel occlusion and where thrombosis occurred at injection site
How may patients with chronic upper limb ischaemia (proximal large vessel disease) present
- Present with activity induced muscle fatigue
- Digital ischaemia secondary to distal embolisation (raynauds phenomenon)
- Ulceration or gangrene secondary to distal embolization
What is subclavian steal syndrome
- Seen with occclusion of the subclavian artery proximal to the origin of the vertebral artery
- The vertebral artery becomes a major collateral to the arm with reversal of the blood flow in the vertebral artery thereby stealing the blood from the posterior cerebral circulation
- Neurological symptoms of vertebrobasilar insufficiency are provoked by exercise of the ipsilateral arm
Etiology of chronic upper limb ischaemia (proximal large vessel disease)
- Atherosclerosis
- Aneurysms
- Arteritis: giant cell and Takayasu’s
- Arterial thoracic outlet syndrome
Which arteries are more commonly affected by atherosclerosis
- Origin of the brachiocephalic and subclavian arteries
- Distal parts of the subclavian, axillary and brachial arteries are involved
- The origin of the Left subclavian is more commonly involved than the right
What structures compress the subclavian artery in arterial thoracic outlet syndrome
-Artery is compressed between the scalene muscles, cervical rib and 1st rib
natural history of arterial thoracic outlet syndrome
chronic arterial trauma leads to fibrosis, focal stenosis, post stenotic dilatation and eventually aneurysm formation with thrombosis and/or distal embolization. Continuous embolization may lead to occlusion of the distal circulation and eventually an unsalvageable situation
Clinical findings of arterial thoracic outlet syndrome
- Discrepancy in blood pressure between the two arms
- Palpable cervical rib
- Palpable subclavian artery in the supraclavicular space
- Bruit and thrill over the subclavian artery
Special investigations for patients with chronic upper limb ischaemia
- Standard xrays of thoracic outlet
- Arterial duplex doppler
Intervention options for chronic upper limb ischaemia
- Percutaneous transluminal angioplasty with or without stenting
- Major bypass procedures
- Treatment of arterial thoracic outlet syndrome: resection of the cervical rib and/or anomalous 1st rib. Damaged segment of the subclavian artery is resected and replaced with a vein or prosthetic graft
Etiology of small vessel/ distal arterial disease
- Vasospasm
- Connective tissue disease: Scleroderma, SLE, Rheumatoid arthritis, polymyositis, dermatomyositis
- Buerger’s disease
- Ischaemia related to occupational injury: professional athletes involved in ball catching, people working with pneumatic tools, constant cold exposure, workers exposed to polyvinylchloride
- Vasculitis: Polyarteritis nodosa, Churg-Strauss, Behcets and HIV vasculitis
- Miscellaneous: Cold agglutinins, cryoglobulins, polycythaemia vera and antiphospholipid antibodies, diabetics with renal failure (Calciphylaxis)
