Acute Limb Ischemia
A 67-year-old man with atrial fibrillation develops sudden severe pain, pallor, and coldness of the right leg over 4 hours. The femoral pulse is strong, but popliteal and pedal pulses are absent. Sensation is reduced over the foot, calf muscles are soft, and power is preserved. What is the most appropriate investigation to plan revascularization?
- A.Venous duplex ultrasonography of the affected leg
- B.Contrast-enhanced CT angiography of the lower limbsCorrect
- C.Bedside ankle-brachial pressure index measurement
- D.Magnetic resonance venography of the pelvic veins
Explanation
A strong femoral pulse with absent popliteal and pedal pulses localises the occlusion to the femoropopliteal segment, and in a patient with atrial fibrillation this is almost certainly a cardioembolic occlusion. The limb is Rutherford class IIa, marginally threatened: there is mild sensory loss without motor deficit and the calf is soft, so it is salvageable with prompt revascularisation, and there is time for imaging before intervention. CT angiography is the investigation of choice because it is fast, widely available and maps the entire arterial tree from the aorta to the pedal vessels, defining the level of occlusion, run-off and whether embolectomy, catheter-directed thrombolysis or bypass is appropriate. Systemic heparin should be started immediately and must not wait for imaging. Venous duplex assesses deep venous thrombosis and would answer the wrong question in an arterial emergency. The ankle-brachial index is the correct screening test for chronic peripheral arterial disease with claudication, but in acute ischaemia with absent pedal signals it adds nothing and delays definitive treatment. Magnetic resonance venography again images veins and is too slow for a threatened limb. If the limb were class III with fixed mottling, a rigid calf and paralysis, it would be irreversible and imaging would be abandoned in favour of amputation.
Why each option
- A.
- Venous duplex evaluates deep venous thrombosis and does not image the arterial occlusion causing this presentation.
- B.
- Correct. CT angiography rapidly maps the level of occlusion and distal run-off in a salvageable acutely ischaemic limb and directs the choice between embolectomy, thrombolysis and bypass.
- C.
- The ankle-brachial index is useful for chronic claudication; with absent pedal pulses in acute ischaemia it adds no information and delays revascularisation.
- D.
- Magnetic resonance venography images veins, is slow to obtain, and has no role in acute arterial occlusion.
Reference: Society for Vascular Surgery Clinical Practice Guidelines on the Management of Acute Limb Ischemia, 2021
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