Acute Limb Ischaemia — the 14-Day Definition, Embolus-versus-Thrombosis Split, STILE-TOPAS Equipoise, and the Compartment Vigilance Rule

A 71-year-old woman with atrial fibrillation wakes with a pale, pulseless, perishingly cold leg and new foot drop; a 64-year-old man with diabetes, prior claudication and a contralateral bruit develops progressive rest pain over 3 days; and a 58-year-old transferred patient arrives 30 hours after onset without prior heparin. One is an embolus to be embolectomised, one is an in-situ thrombosis on chronic disease needing broader revascularisation planning, and one carries the transfer-delay penalty the examiner probes. The viva rewards the candidate who defines the 14-day window, recites the six Ps, splits embolus from thrombosis at the bedside, anticoagulates immediately, chooses surgery versus lysis by occlusion length and bleeding risk, and counsels compartment and reperfusion vigilance — with every number taken from the papers named beside it.^{[1][3][13][11][19]}

Overview & Definition — abrupt loss inside 14 days, vascular emergency

Acute limb ischaemia is a vascular emergency with very high morbidity and mortality.^[1] It is defined by abrupt reduction in arterial perfusion and symptom duration of less than 14 days.^[1] In the general population the incidence is estimated as 14 per 100000, and prognosis depends on the time it takes to diagnose the condition and begin appropriate treatment.^[12] The background prognosis is severe, with amputation rates of up to 25% and in-hospital mortality of 9–15%.^[14] The strategic arc fits one sentence: define by the 14-day window, split embolus from thrombosis, anticoagulate immediately, revascularise by the best-fit modality, and monitor for compartment syndrome and reperfusion injury.^[1][13][19]

Classification — Rutherford labels the trials used, one honesty rule

• The reporting standard exists. Recommended standards for analysing and reporting lower-extremity ischaemia were first published by the Journal of Vascular Surgery in 1986 under the joint vascular societies, are widely used in the peripheral-arterial literature, and were revised to replace the original version.^[2]
• The categories trials use. Transfer cohorts present with Rutherford class IIA and class IIB disease (53.8% IIA, 36.3% IIB in one 87-patient series), revascularisation cohorts enrol classes I, IIa and IIb while excluding class III, and a 345-patient IIa/IIb series reports a 24.3% composite of 30-day death or amputation.^[13][19][17]
• IIb is worse than IIa. Rutherford grade IIb versus IIa carries an odds ratio of 5.51 for 30-day death or amputation — the single number that justifies treating IIb as the immediately threatened leg.^[17]
• The honesty rule. No keeper abstract in this set supplies bedside Doppler-signal cutoffs for the Rutherford bands, so this build grades by the trial labels (I, IIa, IIb, III) and never invents inaudible-versus-audible thresholds.^[2][17]

Each label answers a different viva question — class decides urgency, IIb-versus-IIa decides the death-or-amputation odds, and the 14-day window decides whether the STILE-TOPAS numbers apply.^[17][5][7]

Populations & Denominators — the trial counts that frame every decision

The founders randomise at scale: STILE stops at 393 patients at first interim analysis; the STILE native-artery report randomises 237 (150 lysis, 87 surgery); TOPAS randomises 544 across 113 North American and European sites (272 per group, all within 14 days); TOPAS phase I dose-ranging randomises 213; and Rochester randomises 114 with under-7-day limb-threatening ischaemia.^{[5][6][7][8][9]} The Cochrane pool contributes five trials with 1292 participants using rt-PA or urokinase, and the percutaneous review contributes a single 60-participant trial of ultrasound-accelerated lysis versus standard catheter-directed lysis.^[11][12] The cohort studies contribute 120 embolus-versus-thrombosis patients, 490 thromboembolectomies, 87 transferred patients, 42 delay-study patients, 345 NLR patients, 259 compartment-risk patients, 357 fasciotomy patients, 206 late-presenting patients, and 60 in-stent-occlusion patients.^{[3][15][13][14][17][19][18][22][23]}

Clinical Presentation — six Ps, then the embolus split

The review presentation varies but the six Ps — pain, pallor, pulseless, paraesthesia, paralysis and perishingly cold — are present to some degree, assessment must be quick and efficient, and amputation risk is high.^[1] The embolus declares through a previously normal leg: among 120 patients, 75.8% prove embolic and 24.2% thrombotic, with a normal contralateral pulse in 71.4% of embolic versus 31.0% of thrombotic cases.^[3] Atrial fibrillation marks the embolus (31.9% versus 3.4%), while diabetes, hypertension and hypercholesterolaemia mark the thrombosis; prior intermittent claudication belongs to thrombosis (51.7% versus 3.3%), and immediately threatened ischaemia belongs to embolus (56.0% versus 13.8%).^[3] The population source is atrial fibrillation, where the average annual stroke risk rises 2.3% (30% lethal) and annual acute limb ischaemia incidence runs 0.4% (16% lethal).^[4] The aortic saddle embolus declares through both legs at once — rest pain in every patient with sensory or motor deficit in two-thirds — overwhelmingly on atrial fibrillation, flutter, rheumatic or valvular disease.^[21]

Differential Diagnosis — aetiology first, level second, mimics last

Split embolus (sudden, previously normal leg, contralateral pulse present, atrial fibrillation, no claudication) from in-situ thrombosis (diabetes, hypertension, hypercholesterolaemia, prior claudication, contralateral disease) before choosing the incision.^[3] Split native-artery occlusion from graft occlusion and from femoropopliteal in-stent occlusion — the in-stent subgroup (60 patients) shows no 5-year survival, patency or amputation-free difference between endovascular and open revision, with open surgery costing a longer stay (11.3 versus 4.4 days).^[5][23] Split the aortic saddle embolus (bilateral rest pain with deficits, infrarenal aortic embolus in 94%) from unilateral disease — it wants bilateral transfemoral embolectomy, carries 33% overall mortality, and still infarcts kidneys and amputates limbs.^[21] Split acute ischaemia inside 14 days (STILE-TOPAS eligible) from the late-presenting leg (revascularise even at one week) from chronic critical ischaemia (outside every number above).^[5][7][22]

Name the aetiology aloud before ordering the scan — the viva rewards the candidate who separates what the cause decides from what only timing and anatomy decide.^[3][10]

Clinical & Bedside Assessment — event, leg, category, clock

Anchor the assessment on four facts: when perfusion stopped (inside or beyond 14 days), which leg and level, which Rutherford label the leg resembles (I, IIa, IIb), and what the clock already cost.^[1][13][17] Date onset precisely — occlusion beyond 24 hours more than doubles death-or-amputation odds, and the largest delay sits between symptom onset and first doctor contact (median 24 hours, range up to 1200).^[16][14] Feel the contralateral pulses, ask about claudication, diabetes, hypertension and atrial fibrillation — the bedside split that predicts embolus versus thrombosis.^[3] Measure neurology explicitly — IIb versus IIa multiplies 30-day death-or-amputation more than fivefold, and a pre-operative neutrophil-to-lymphocyte ratio at or above 5.4 detects that composite with 90.5% sensitivity and 73.6% specificity.^[17] Start systemic anticoagulation at suspicion — the accepted treatment pairs it with timely reperfusion, yet transfer series show only 87.4% started on heparin and barely half therapeutic before revascularisation.^[13]

Investigations — CTA to map, labs to warn, angio to finish

Map the occlusion with CT angiography — the saddle-embolus series images every patient by CTA and recommends it for diagnosis, and delay work shows imaging before operation adds meaningful time, so order it without dithering once the diagnosis is clinical.^[21][14] Complete the operation with angiography — avoiding completion angiography predicts reocclusion, and femoral exploration with embolectomy remains the workhorse from aortic down to distal occlusion.^[15][22] Draw the warning labs early — CK and myoglobin peak 24–48 hours after surgery (median CK 29370 units per litre, myoglobin 8.17 mg per litre in acute cases), and compartment-risk concentrates with CK above 510, platelets below 200000, weight above 83 kg and liver dysfunction.^[20][19] Add the inflammatory marker where available — higher neutrophil-to-lymphocyte ratio predicts 30-day death-or-amputation with an area under the curve of 0.86.^[17]

Management — Initial: anticoagulate now, revascularise without delay

Give the accepted treatment exactly: immediate systemic anticoagulation and timely reperfusion to restore blood flow.^[13] Give the adherence gap exactly: 87 patients transferred to a level-I vascular programme — 87.4% started on heparin before transfer, only 57.9% therapeutic by activated partial thromboplastin time before revascularisation — and starting anticoagulation beyond 48 hours raises 30-day reintervention to 66.7% against 23.5% inside 6 hours.^[13] Give the delay anatomy exactly: 42 patients with median age 73 — 24 hours from onset to first doctor contact, 324.5 minutes from vascular evaluation to revascularisation for direct-to-theatre cases against 822 minutes when imaging intervenes, and 5621 minutes median for the thrombolysis subgroup — closing with six above-ankle amputations and four deaths at 30 days.^[14] Set the triage rule the examiner wants: heparin at suspicion, transfer to a revascularisation centre, CTA to map, and reperfusion the same sitting — because prognosis depends on time to diagnosis and treatment.^[13][12]

The resolution is the viva sentence: an acutely ischaemic leg gets systemic anticoagulation at suspicion and reperfusion without delay, since every hour converts salvage into reintervention, amputation or death.^[13][14]

Management — Surgery versus thrombolysis: equipoise with trade-offs

Give STILE exactly: 393 patients with native-artery or graft occlusion randomised to optimal surgery or catheter-directed lysis — catheter placement fails in 28% (counted as lysis failures) — 30-day outcomes favour surgery (p less than 0.001) through less ongoing or recurrent ischaemia, yet 0–14-day ischaemia shows lower amputation with lysis and shorter stay, and 6-month amputation-free survival favours lysis in acute presenters while chronic presenters favour surgery.^[5] Give STILE-native exactly: 237 iliac-femoral or femoropopliteal native-artery occlusions (150 lysis, 87 surgery) — catheter delivery succeeds in 78% with a smaller operation in over half — yet 1-year recurrent ischaemia runs 64 versus 35% and major amputation 10 versus 0% against lysis, worst with femoropopliteal occlusion, diabetes or critical ischaemia.^[6] Give TOPAS exactly: 544 patients within 14 days (272 per group) with catheter-directed recombinant urokinase — recanalisation in 79.7% with complete dissolution in 67.9% — amputation-free survival 71.8 versus 74.8% at 6 months and 65.0 versus 69.9% at 1 year (both non-significant) — surgery needs 551 open procedures against 315 with lysis, at the price of major haemorrhage 12.5 versus 5.5% with four intracranial bleeds (1.6%, one fatal) against none.^[7] Give TOPAS phase I exactly: the 4000-units-per-minute regimen maximises lysis (71% complete at mean 23 hours) against bleeding — 1-year mortality 14 versus 16% and amputation-free survival 75 versus 65% tied — with fewer and smaller operations after lysis.^[8] Give Rochester exactly: 114 patients inside 7 days — thrombus dissolves in 70% — limb salvage ties at 82% at 12 months while survival favours lysis 84 versus 58% (p equals 0.01) through fewer in-hospital cardiopulmonary complications (16 versus 49%).^[9] Give the Cochrane synthesis exactly: five trials, 1292 participants — no clear differences in limb salvage, amputation or death at 30 days, 6 months or 1 year — with lysis carrying more major haemorrhage (odds ratio 3.22) and distal embolisation (odds ratio 31.68) but a greater reduction in the planned intervention (odds ratio 9.06).^[11]

The choosing resolution: offer lysis for longer occlusions (the 30-cm threshold favours lysis above and surgery below), for high cardiopulmonary risk, and where shrinking the operation matters — and offer surgery for native femoropopliteal disease with diabetes or critical ischaemia, for failed catheter placement, and where bleeding risk forbids lysis.^{[10][6][9][11]}

Management — Endovascular adjuncts: what the reviews actually support

Give the percutaneous verdict exactly: one 60-participant trial of ultrasound-accelerated lysis versus standard catheter-directed lysis — no difference in amputation, major bleeding, clinical success or adverse effects on very-low-certainty evidence — with no randomised evidence at all for percutaneous thrombectomy.^[12] Give the in-stent verdict exactly: 60 acute legs with femoropopliteal in-stent occlusion — endovascular and open bypass tie at 5 years on survival, patency, reintervention and amputation-free survival — with open surgery costing a longer stay.^[23] Consider endovascular-first in the high-perioperative-risk leg — the review position that endovascular treatment belongs in higher-risk patients — while recognising the evidence cannot yet rank thrombectomy or accelerated lysis above standard lysis or surgery.^[1][12]

Management — Technique: embolectomy, completion imaging, fasciotomy judgment

Explore the femoral artery with an embolectomy catheter as the workhorse — the late-presenting series uses it from aortic to distal occlusion — and finish with completion angiography, since skipping it predicts reocclusion.^[22][15] Treat the saddle embolus by bilateral transfemoral embolectomy after CTA mapping — the preferred treatment in the 18-patient series — expecting internal-iliac re-embolisation, pelvic ischaemia vigilance, fasciotomy in half, renal failure in over a fifth, and substantial mortality even after technically successful clearance.^[21] Perform fasciotomy in 45.6% of very-late presentations for existing or impending compartment syndrome — yet judge prophylactic fasciotomy against its trial: no amputation-free-survival gain with higher early mortality and more wound infection.^[22][18]

Complications & Pitfalls — the six traps

Set the compartment expectation first: post-reperfusion compartment syndrome develops in 10.8% of revascularised legs, predicted independently by weight above 83 kg, moderate-to-severe liver disease, low platelets and CK above 510 — so stratify before closing.^[19]

The anticoagulation-delay trap — transferring without heparin when only 87.4% start it and barely half reach therapeutic levels, with beyond-48-hour starts more than doubling reintervention.^[13] The single-winner trap — promising surgery or lysis as universally superior when the randomised pool ties on salvage, amputation and death and trades bleeding against reintervention.^[11] The Doppler-invention trap — quoting Rutherford signal thresholds this set never verified, when the examined numbers are the IIb-versus-IIa odds ratio and the NLR cutoff.^[2][17] The prophylactic-fasciotomy trap — cutting routinely when 30-day amputation-free survival ties (hazard ratio 0.93) while early mortality quadruples and wound infection triples.^[18] The reperfusion blind-spot trap — ignoring CK, myoglobin, urine output and compartment pressures when CK peaks near 30000, dialysis-requiring renal failure follows successful revascularisation, and reperfusion injury multiplies death odds nearly seventeenfold.^[20][16] The late-leg abandonment trap — scheduling primary amputation for the week-old leg when late revascularisation still restores perfusion with 13.1% amputation, 5.8% mortality and 80% 5-year estimates.^[22]

Prognosis & Disposition — the numbers that set expectations

Special Populations — contexts that change the emphasis

The late-presenting leg runs on the 206-patient series: cardiac disease causes most cases, femoral exploration with embolectomy leads, fasciotomy supports nearly half, surgical-site infection touches 8.25% with repeat embolectomy in 10.68% — and revascularisation stays warranted even one week out.^[22] The saddle-embolus patient carries the highest stakes: aortic embolism below the renal arteries in 94%, CTA-mapped bilateral transfemoral embolectomy, fasciotomy in 9 of 18, six amputated limbs in four patients, renal failure in four, and one-third dead overall.^[21] The in-stent-occlusion leg ties either way at 5 years — choose endovascular for shorter stay or bypass for anatomy, knowing patency and amputation-free survival match.^[23] The thrombotic leg with diabetes, long occlusion and prior revascularisation carries the worst composite — thrombotic aetiology alone predicts all three of reocclusion, amputation and mortality, over-24-hour occlusion and diabetes trend add death-or-amputation risk, prior revascularisation raises reintervention, and high NLR adds risk, while statin or anticoagulant pre-treatment associates with risk reduction.^{[15][16][17][13]} The high-cardiopulmonary-risk leg favours an initial lytic strategy by the Rochester survival mechanism — fewer in-hospital cardiopulmonary complications — priced against haemorrhage and intracranial bleeding.^[9][7]

Evidence, Guidelines & Regional Differences — the four stories and who led them

The definition story is review-to-standards: the 2025 review fixes the under-14-day window with six-P presentation and three modalities, while the 1997 Rutherford standards provide the reporting language every trial inherits — level-5 and level-4 foundations, not outcome claims.^[1][2] The randomised story is STILE-to-TOPAS-to-Rochester: STILE proves surgery wins at 30 days yet lysis wins amputation-free survival in acute presenters; TOPAS proves lysis shrinks surgery without moving amputation-free survival while charging haemorrhage; Rochester proves lysis saves lives through fewer cardiopulmonary complications — synthesised by Cochrane into equipoise with a bleeding price.^{[5][7][9][11]} The systems story is transfer-to-delay: pretransfer heparin gaps raise reintervention, patient delay dominates the clock, and imaging-to-theatre handoffs add hours — fixable without a single new device.^[13][14] The vigilance story is compartment-to-reperfusion: one-in-ten compartment rates with four independent predictors, prophylactic fasciotomy without survival gain, CK near 30000 with dialysis-requiring renal failure, and reperfusion injury as a death predictor — the postoperative bundle that decides the outcome as much as the inflow.^{[19][18][20][16]} The current container across these papers is timely reperfusion after immediate anticoagulation as the comparator every result assumes; regional service patterns vary, so name the trial beside every protocol claim, and note the set's stated honesty — the ESVS editions carry no quotable abstract here, so no ESVS number appears above.^[13][12]

Exam Pearls — the one-liners that score

• Under 14 days with six Ps defines it; 14 per 100000 with 25% amputation and 9–15% mortality frames it.^[1][12][14]
• Embolus means normal opposite pulse, atrial fibrillation and no claudication; thrombosis means claudication, diabetes and contralateral disease.^[3]
• Heparin at suspicion with timely reperfusion; beyond 48 hours more than doubles reintervention.^[13]
• Five trials, 1292 patients: salvage, amputation and death tie; bleeding OR 3.22, embolisation OR 31.68, smaller operation OR 9.06.^[11]
• STILE 393: surgery wins 30 days, lysis wins acute 6-month amputation-free survival; native-artery 1-year amputation 10 versus 0% favours surgery.^[5][6]
• TOPAS 544: amputation-free 71.8 versus 74.8% tied; 551 versus 315 operations; intracranial bleed 1.6% versus none.^[7]
• Rochester 114: salvage tied 82%, survival 84 versus 58% through fewer cardiopulmonary events.^[9]
• IIb versus IIa multiplies death-or-amputation 5.51-fold; NLR 5.4 detects it at 90.5% sensitivity.^[17]
• Compartment strikes 10.8%; prophylactic fasciotomy ties survival while quadrupling early mortality — reserve it.^[19][18]
• The late leg still earns revascularisation at one week: 13.1% amputation, 5.8% mortality.^[22]

Revision summary

Acute limb ischaemia is defined inside 14 days with six-P presentation and framed by 14-per-100000 incidence with severe background risk. Embolus-versus-thrombosis bedside split directs the operation, heparin starts at suspicion with delay punished in reintervention, and CTA maps the occlusion. STILE-TOPAS-Rochester with Cochrane synthesis resolve into equipoise — lysis shrinks surgery at a bleeding price, surgery protects native arteries durably, and occlusion length with bleeding risk chooses. Compartments strike one in ten with four predictors, prophylactic fasciotomy earns restraint, reperfusion injury predicts death, and the late leg still earns its revascularisation.^{[1][3][13][11][19][22][17]}

rest pain in all with deficits in 67%, AF/flutter 89%, below-renal embolus in 94% (PMID 30476605).^[8][21] Treat saddle embolism by bilateral transfemoral embolectomy in 83% after CTA mapping, expecting iliac re-embolisation in 58% (PMIDs 30476605).^[21] Weigh prior revascularisation (46.5% reintervention), high NLR and diabetes trend with statin/anticoagulant-associated risk reduction (PMIDs 29477682, 34112572).^[13]