Acute limb ischaemia in a patient with a popliteal aneurysm and undiagnosed atrial fibrillation
Mr E, 70, is referred at 06:30 with sudden severe left calf and foot pain that woke him at 20:30 the previous evening, so about 10 hours old. The leg is pale to mid-calf and cold below the knee; light touch is reduced over the first web space, but ankle dorsiflexion and toe movement are intact. He has rest pain and cannot weight-bear. Hand-held Doppler shows a normal femoral signal, a monophasic popliteal signal and no signal at the dorsalis pedis or posterior tibial; venous filling is sluggish. Ankle–brachial index is 0.35 and toe pressure 32 mmHg. Ultrasound eight months earlier showed a 3.8 cm left popliteal aneurysm containing mural thrombus. He has hypertension, a previous transient ischaemic attack and an eGFR of 42, and takes aspirin 75 mg. The ECG shows atrial fibrillation at 96 beats per minute and he is not anticoagulated. He is afebrile, haemodynamically stable, with no bleeding history and no contraindication to heparin.
1. Classify the limb and justify whether he needs immediate theatre or whether imaging can come first.
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Rutherford IIa - marginally threatened. The features are rest pain, absent pedal Doppler signals, a toe pressure of 32 mmHg (below the 40–50 mmHg threshold) and reduced light touch, but no motor deficit. Rutherford IIb is rest pain with a motor deficit and inaudible arterial and venous signals; that limb goes to theatre without imaging.
Because this is IIa, imaging is permissible and useful - but it is on the clock, not a leisurely work-up. Start unfractionated heparin immediately (bolus followed by infusion) unless contraindicated, give analgesia, site a catheter, take blood for group and save, clotting, renal function and glucose, keep him nil by mouth, and consent him for revascularisation, bypass and amputation. Then get CT angiography of the whole leg to define the level of occlusion, the state of the run-off and whether the popliteal aneurysm is the source. The target is revascularisation within six hours of presentation.
The judgement is not to over-investigate. Duplex alone may suffice if the patient is deteriorating or the angiography suite is busy, and any new weakness, fixed mottling or loss of venous signals converts him to IIb and to immediate theatre. Equally, do not be lulled by a warm thigh and a palpable popliteal - the disease is below the knee.
2. Weigh catheter-directed thrombolysis against surgical thrombectomy with popliteal repair for this patient, and state what you would do.
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Catheter-directed thrombolysis: less invasive, dissolves distal thrombus that a balloon cannot reach, and is attractive if operative risk is high. But it takes 12–24 hours to work, carries a bleeding risk (his eGFR of 42 and age matter), needs intensive monitoring, and does not treat the underlying popliteal aneurysm - so recurrence is likely. With 10 hours of ischaemia and viable-but-threatened tissue, time is the currency.
Surgery: prompt restoration of flow, direct clearance of the aneurysm sac and its mural thrombus, and a definitive repair that prevents the next event. The downside is anaesthetic and wound morbidity and the need for a conduit.
My decision: take him to theatre for on-table angiography, proximal and distal control, arteriotomy over the popliteal aneurysm, Fogarty thrombectomy of the popliteal and tibial vessels, and completion angiography. Then repair the artery - preferably an autologous vein interposition or bypass, since prosthetic material in an acutely ischaemic field with a contaminated risk profile is inferior; ligation with bypass is an alternative if the sac is difficult. Adjunctive intraoperative thrombolysis is reasonable if distal thrombus persists. Postoperatively, start therapeutic anticoagulation for the atrial fibrillation once haemostasis is secure, add a statin, stop smoking, and document that the contralateral leg and aorta need imaging.
3. He also has a 4.6 cm infrarenal aortic aneurysm and a 2.6 cm right popliteal aneurysm. How does this admission change their management?
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This admission converts a set of incidental findings into a coherent surveillance and intervention plan.
The left popliteal aneurysm (3.8 cm) has now caused a threatened limb. It is repaired during this admission, as part of the revascularisation, not left for later - an untreated popliteal aneurysm has a high risk of rethrombosis and major amputation.
The right popliteal aneurysm (2.6 cm) is above the 2 cm threshold generally used to recommend repair, particularly with any mural thrombus, because the consequences of thrombosis or embolisation are limb-threatening and the elective operation is relatively low risk. Options are autologous vein bypass or, if the anatomy is suitable and the patient prefers, an endovascular stent graft, accepting the need for ongoing surveillance. Duplex should be done now to confirm size and thrombus burden. Smaller aneurysms (under 2 cm) without thrombus can be surveilled six- to twelve-monthly.
The 4.6 cm aortic aneurysm in a man does not meet the 5.5 cm repair threshold. Surveillance with ultrasound or CT at 12 months is appropriate, with earlier review if growth exceeds about 1 cm per year or symptoms develop. Two caveats: if any planned bypass depends on aortoiliac inflow, the aorta must be imaged properly first; and his cardiac risk, renal function and blood pressure need optimisation before any elective aortic work.
Beyond the arteries: this is a marker of systemic vascular disease. He needs smoking cessation, a statin, blood pressure control, anticoagulation for atrial fibrillation, and screening of the contralateral limb and aorta. Write it all down and hand the plan to the patient and the vascular nurse specialist, because the risk now is that everyone treats the leg and forgets the aorta.