10th March 2024

Peripheral Vascular Disease

Acute Limb Ischaemia

Acute limb ischaemia is a life-limb-threatening condition caused by a rapid or sudden decrease in limb perfusion, endangering tissue viability. Two possible events are implicated in the cause. Arterial thrombosis originating from a pre-damaged atherosclerotic site represents 85% of causes, and non-atherosclerotic peripheral embolism accounts for 10-15%. The incidence is approximately 1.5 cases per 10,000 persons per year. The most common aetiologies are:

• Native arterial thrombosis: atherosclerotic plaque, aneurysm, dissection, hypercoagulability. 
• Injury: iatrogenic or traumatic
• Thrombosis following intervention
• Embolism: arterial or paradoxical
• Peripheral vasoconstriction/ vasospasm 

Most patients with acute limb ischaemia will have a background of peripheral artery disease (PAD) and will experience intermittent claudication caused by a mismatch between active muscle demand and blood supply; and atypical lower extremity pain. A threatened limb is referred to those patients whose arterial blood flow is insufficient to meet the demand of resting muscle or tissue. 

Clinical presentation

Presentation may be acute or acute-on-chronic limb ischaemia, depending on the onset, location and the possible collateral vessels available. 

Acute-on-chronic limb ischaemia is common in patients with background of peripheral artery occlusive disease or previous revascularisation. Symptoms will have an increasing course and are similar to those of PAD. Acute limb ischemia, on the other hand, will present with rapidly evolving symptoms which can be remembered as the six Ps:

• Pain
• Pallor 
• Poikilothermia (inability to maintain a constant core temperature) 
• Pulseless 
• Paraesthesia 
• Paralysis 

Diagnosis

Diagnosis can be made using clinical categories or with the use of ankle-brachial pressure index (see Table 3). After categorising based on cause and severity, consideration can be made whether to proceed with additional investigations. The clinical categories used are: 

• Viable or marginally threatened: no sensory loss or muscle weakness, and both arterial and venous Doppler signals are audible.
• Immediately threatened: Sensory loss involves more than the toes; rest pain and mild-to-moderate muscle weakness are present. Arterial Doppler signals are usually inaudible, and venous Doppler signals are audible.
• Irreversibly ischemic: profound sensory loss and muscle weakness (paralysis and possible rigor). Arterial and venous Doppler signals are inaudible. 

CT angiography or catheter-based arteriography are the investigations of choice, the second one providing a therapeutic option. 

Table 3. Ankle-Brachial Pressure Index interpretation. 

Management

The success of treatment depends on several factors, including the aetiology, location, duration of symptoms, availability of autologous vein for bypass grafting and suitability of the patient for surgery or intervention. The management of acute limb ischaemia is done by catheter-directed thrombolysis (with or without endovascular intervention) or surgical revascularisation. 

Raynaud’s Phenomenon

Raynaud’s phenomenon (RP) is defined as a vascular response to cold temperature or emotional stress that is above the normal physiological response. The pathogenesis of RP is a complex interplay of different factors, including genetic, neural, vascular and intravascular factors. This vasospastic condition affects around 5% of the population, is more common in women and can be classified as primary or secondary. Primary RP is more common before the age of 30 in contrast to secondary RP, which usually presents after the age of 40. Secondary causes include:

• Vascular
• Occupational
• Autoimmune
• Drug/chemical-related
• Conditions associated with increased plasma viscosity and reduced digital perfusion
• Other causes, e.g., carpal tunnel syndrome, frostbite, and hypothyroidism

Clinical presentation

RP presents as a characteristic colour change in hands and sometimes feet associated with cold temperatures or emotional stress. Most patients will not present to a healthcare provider during the episodes due to the regular short durations but will capture the episodes on their mobile phone or describe the typical clinical picture. The classical triad of colour change will traverse from white (pallor) to blue (cyanosis) to red before turning back to the patient’s regular skin colour. 

Diagnosis

RP is considered a symptom, not a diagnosis; however, the cause should be investigated to identify whether this is primary or secondary. The burden of digital complications should be considered to aid the decision on whether drug or surgical intervention is needed. In primary RP nailfold capillaroscopy, FBC, ANA and ESR should be normal. In secondary RP or systemic sclerosis, these will be abnormal. Once the cause is established, the management will be tailored to the underlying cause and consideration for symptom control with drugs or surgical treatment. 

Management

Initial management of primary RP involves conservative measures such as patient education to avoid the cold, hand-warming gloves and smoking cessation. After this, first-line medications such as calcium channel blockers, phosphodiesterase inhibitors, ARBs, SSRIs, alpha-blockers, ACE-I and topical nitrates can be used. In refractory RP or where there is digital ulceration, intravenous prostanoid can be used. When all medical treatments fail to control RP and ulceration and critical ischemia begins to occur, a digital sympathectomy should be considered.

References

• Fluck, F. et al. 2020. Current treatment options in acute limb ischemia. In RöFo-Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren. Vol. 192, No. 04, pp. 319-326.
• Mitchell, M. and Carpenter, J. 2020. Clinical features and diagnosis of acute lower extremity ischemia. In UpToDate.
• Van, D. et al. 2018. Acute limb ischemia.Revue medicale de Liege. 73(5-6), pp.304-311.
• Haque, A. and Hughes, M. 2020. Raynaud’s phenomenon. Clinical Medicine. Available at https://doi.org/10.7861/clinmed.2020-0754 
• Herrick, A.L et al. 2020. New perspectives in the imaging of Raynaud’s phenomenon. European Journal of Rheumatology. Available at https://doi.org/10.1177/2397198319826467