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Long Case Viva Questions on Peripheral Arterial Disease (PAD)

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SECTION 1: Introduction and Epidemiology

• PAD is atherosclerotic occlusive disease of the peripheral (predominantly lower limb) arteries, causing a spectrum from asymptomatic stenosis to limb-threatening ischemia.
• It is age-dependent, underdiagnosed, and undertreated. The PARTNERS program found PAD in 29% of primary care patients aged >70 or aged 50-69 with smoking/diabetes history.
• More than 50% of patients with PAD are entirely asymptomatic.
• Clinically significant because it is a powerful independent predictor of mortality - PAD patients have a ~4-fold higher risk of MI and 2-3x higher risk of stroke vs. non-PAD patients. Approximately 40% of patients with atherosclerotic vascular disease have disease in more than one vascular bed.
• Patients with critical limb ischemia (CLI) have an annual mortality rate of ~25%.

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• Modifiable: Cigarette smoking (single most important), diabetes mellitus, hypertension, hyperlipidaemia, obesity, sedentary lifestyle.
• Non-modifiable: Age (>50 years), male sex, family history, ethnicity (higher in Black populations).
• Emerging: Hyperhomocysteinaemia, elevated lipoprotein(a), chronic kidney disease (CKD), inflammatory markers (CRP).
• Smoking is particularly important - it roughly doubles the risk of PAD and is directly associated with claudication severity and amputation risk.

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SECTION 2: History Taking

• Claudication history:
  • Onset, site, character of pain (cramping/aching in muscle groups)
  • Claudication distance (how far before pain starts) - note this varies little day to day
  • Relieved by standing still within 5 minutes (differentiates from nerve compression, which requires sitting)
  • Pain not present on first step (unlike osteoarthritis)
  • Worsening with uphill walking, increased speed, carrying weights
• Rest pain:
  • Pain in foot/calf at rest, worse at night, worse with leg elevation
  • Patient hangs foot out of bed or sleeps in chair for relief (gravity effect)
  • Indicates more severe ischemia than claudication
• Skin changes: Non-healing ulcers, blackened tissue (gangrene)
• Cardiovascular review: Ask about chest pain, dyspnoea, palpitations, TIA/stroke, renal impairment (co-existing atherosclerosis)
• Risk factor assessment: Smoking history (pack-years), diabetes management, hypertension and medications, lipid profile, family history
• Functional impact: How has claudication affected occupation, social, and leisure activities?
• Erectile dysfunction - may indicate aortoiliac disease (Leriche syndrome)

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• Leriche syndrome results from aortoiliac occlusion.
• Classic triad: (1) Buttock and thigh claudication; (2) absence of femoral pulses bilaterally; (3) erectile dysfunction (sexual impotence) in men due to internal iliac artery insufficiency.
• The level of claudication is one anatomical level below the arterial obstruction - aortoiliac disease causes thigh and buttock claudication.

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SECTION 3: Clinical Examination

• General inspection: Pallor, cyanosis, tar-stained fingers (smoking), xanthelasma, corneal arcus
• Inspect the limbs: Skin colour (pallor, cyanosis, dependent rubor "sunset foot"), hair loss, muscle wasting, trophic skin changes, ulcers, gangrene
• Buerger's test:
  • Elevate both legs to 45 degrees for 1-2 minutes - ischaemic limb goes pale (positive)
  • Then hang legs down - ischaemic limb flushes deep red-purple (reactive hyperaemia/dependent rubor = "sunset foot" sign)
  • Buerger's angle = the angle at which the limb becomes pale; <20 degrees = severe ischemia
• Capillary refill time: Press heel/toe pulp for 5 seconds; normal 2-3 seconds; prolonged >10 sec in severe ischemia
• Pulses: Systematically palpate femoral, popliteal, posterior tibial, dorsalis pedis
  • Compare bilateral femoral pulses
  • Note: pulse distal to an arterial occlusion is usually absent; collaterals may occasionally allow palpable distal pulses even with stenosis
  • Exercise (walking to claudication) will cause a distal pulse to disappear as vasodilation occurs below the obstruction
• Auscultation: Bruit over aorta, iliac, femoral arteries (indicates turbulent flow, suggests stenosis). Note: tight stenoses/complete occlusions may be silent.
• Abdomen: Palpate for aortic aneurysm (may coexist with lower limb occlusive disease)
• Venous guttering: A chronically ischaemic leg elevated will show collapsing, guttered veins

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SECTION 4: Investigations

• ABI = highest ankle systolic pressure (dorsalis pedis, posterior tibial, or peroneal) / highest ipsilateral brachial systolic pressure.
• Measured using a hand-held Doppler probe and sphygmomanometer.
• Interpretation:
  • 0.9-1.4: Normal
  • <0.9: Hemodynamically significant arterial lesion (PAD diagnosis)
  • 0.5-0.9: Claudication range
  • <0.4: Critical limb-threatening ischemia (CLTI)

  • 1.4: Arterial calcification/incompressibility (falsely elevated - seen in diabetes, chronic renal failure)

• A drop of >20% from resting ABI after exercise is indicative of flow-limiting arterial disease (exercise ABI is useful when resting ABI is normal but symptoms suggest PAD).
• Pitfall: In diabetics with medial calcification, vessels are non-compressible. Use toe-brachial index (TBI) instead - toe (digital) arteries are rarely affected by calcification. TBI <0.6 suggests significant arterial disease.

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• ABI with hand-held Doppler (confirms diagnosis, grades severity)
• Blood glucose, HbA1c (diabetes screening/monitoring)
• Full blood count (anaemia worsens ischemia by reducing O2 delivery)
• Lipid profile (identify and quantify dyslipidaemia)
• Renal function (coexisting renovascular disease; relevant for contrast use)
• ECG (coexisting coronary artery disease is present in ~50%)

• Duplex Doppler Ultrasonography (DUS): First-line non-invasive imaging. Localises stenosis, determines degree using peak systolic velocity ratio (PSVR). PSVR ≥2.4 = obstructive disease; PSVR ≥3.0 = functionally significant. Useful for graft/stent surveillance.
• CT Angiography (CTA): Best anatomical detail, 3D reconstruction, invaluable for pre-operative planning. Limitation: iodinated contrast (risk of nephropathy, especially in diabetics), ionising radiation. Metformin must be withheld periprocedurally.
• MR Angiography (MRA): No ionising radiation, no iodinated contrast. Uses gadolinium (caution in severe CKD - nephrogenic systemic fibrosis). Good for aortoiliac and femoropopliteal segments.
• Digital Subtraction Angiography (DSA): Gold standard for arterial anatomy. Access via Seldinger technique (usually common femoral artery). Provides dynamic flow information and can be combined with endovascular treatment. Complications: haematoma, false aneurysm, thrombosis, arterial dissection, distal embolisation, renal dysfunction, allergic reaction (~5%). Reserved for when intervention is planned.

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• A technique for gaining percutaneous arterial access.
• Steps: (1) Needle puncture of the artery (usually CFA); (2) guidewire inserted through needle; (3) needle withdrawn over wire; (4) sheath/catheter threaded over wire; (5) wire removed.
• Allows introduction of catheters, sheaths, and interventional devices without surgical cut-down.

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SECTION 5: Classification

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• CLTI (previously called critical limb ischemia/CLI) refers to patients with ischaemic rest pain and/or ischaemic ulceration/gangrene (tissue loss).
• Defines the highest-risk end of the PAD spectrum with an imminently threatened limb.
• Requires urgent vascular assessment and revascularisation to prevent major amputation.
• These patients have the lowest ABIs (<0.4) and the highest annual mortality (~25%).
• Bilateral co-morbidities (coronary, cerebral, renal) are almost universally present.

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SECTION 6: Management

• Smoking cessation - single most effective intervention; dramatically slows progression
• Supervised exercise rehabilitation - structured walking programme (30-45 min, 3x/week); increases pain-free walking distance by improving collateral flow and muscle metabolism
• Antiplatelet therapy - aspirin 75-100 mg/day or clopidogrel 75 mg/day (reduces cardiovascular events, not claudication per se)
• Statins - reduce cardiovascular events; some improvement in walking distance
• Antihypertensives - ACE inhibitors preferred (also shown to reduce cardiovascular events in HOPE trial)
• Diabetes control - tight glycaemic control
• Cilostazol (PDE-3 inhibitor) - only drug with evidence of improving claudication: increases maximal walking distance by 54% vs placebo. Contraindicated in heart failure. Approved by FDA for claudication.
• Pentoxifylline - no randomised data showing benefit over placebo; not recommended.
• Foot care - especially in diabetics to prevent ulceration

• Indications: lifestyle-limiting claudication not responding to 3-6 months of conservative treatment, rest pain, tissue loss
• Angioplasty ± stenting (PTA): First-line for short segment lesions (TASC A/B); shorter recovery, less morbidity. Risk of restenosis from neointimal hyperplasia.
• Surgical bypass: For long-segment occlusions (TASC C/D), failed endovascular procedures; e.g., aortobifemoral bypass (aortoiliac), femoro-popliteal bypass.
• Graft material: Autologous vein (long saphenous - best patency) vs. synthetic (PTFE or Dacron - acceptable above knee, poor below knee).

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• Cilostazol is a phosphodiesterase type III (PDE-3) inhibitor. It inhibits platelet aggregation and causes arterial vasodilation by preventing breakdown of cAMP.
• Approved by the FDA for treatment of intermittent claudication (1999).
• In randomised trials comparing cilostazol 100 mg twice daily vs. pentoxifylline vs. placebo, cilostazol improved maximum walking distance by 54% vs. 30% for pentoxifylline and 34% for placebo.
• Contraindication: Heart failure of any severity (increased mortality in trials with PDE inhibitors in heart failure).
• Dose: 100 mg twice daily.

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• Lifestyle-disabling intermittent claudication not improved after 3-6 months of maximal conservative therapy
• Ischaemic rest pain (Fontaine III / Rutherford 4)
• Tissue loss - non-healing ulceration (Fontaine IV / Rutherford 5)
• Gangrene with limb salvage potential (Rutherford 6)
• In CLTI, revascularisation should be performed urgently

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• TASC (Trans-Atlantic Inter-Society Consensus) classifies lesions by morphology to guide revascularisation strategy:
  • TASC A: Short single stenoses; recommended endovascular (PTA ± stenting)
  • TASC B: Multiple short stenoses or single longer stenosis; endovascular preferred
  • TASC C: Multiple long stenoses or single occlusion; surgery preferred
  • TASC D: Complete occlusions, long segment or aortoiliac involvement; surgery recommended
• Endovascular has lower short-term morbidity; surgery has better long-term patency for complex lesions.

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SECTION 7: Acute Limb Ischaemia (ALI) - Viva Extension

• Pain - sudden severe onset
• Pallor - white/pale limb
• Pulselessness - absent distal pulses
• Paraesthesia - pins and needles (early nerve ischaemia)
• Paralysis - motor deficit (late/severe; urgent sign)
• Perishing cold (Poikilothermia)

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• Immediate: IV heparin to prevent propagation; analgesia; urgent vascular surgical referral
• Imaging: Emergency DSA or duplex to determine level and cause
• Surgical embolectomy (Fogarty balloon catheter) - for embolic occlusion, viable limb
• Catheter-directed thrombolysis - for thrombotic occlusion or if surgical risk is high; slower, requires ICU monitoring, risk of haemorrhage
• Surgical bypass - for thrombotic occlusion with anatomical disease
• Amputation - if limb is non-viable (irreversible ischemia with fixed mottling, rigor, paralysis)
• Post-procedure: Investigate and treat the source (echocardiogram if AF/cardiac embolism; anticoagulation)

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SECTION 8: Complications and Prognosis

• Progression to rest pain and CLTI
• Amputation (major or minor) - <5% of claudicants reach amputation; much higher in CLTI
• Myocardial infarction (fourfold risk vs. non-PAD)
• Stroke (2-3x risk)
• Cardiovascular death (leading cause of death in PAD patients)
• Reduced quality of life and functional decline

• Apparent "improvement" in IC over time does NOT reflect disease improvement - it often reflects functional decline (patients walk slower/shorter distances to avoid pain).
• PAD is a progressive disorder causing significant decline in quality of life.
• ~25% of claudicants deteriorate, 25% improve (often due to functional decline), 50% stable.
• Fewer than 5% will ever require amputation.
• The dominant risk is cardiovascular mortality - not limb loss.
• The lower the ABI, the greater the cardiovascular event risk.

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SECTION 9: Special Situations

• PAD in diabetics is more distal (tibial/peroneal vessels affected preferentially), more diffuse, and often bilateral.
• Neuropathy may mask ischemic pain - patient may present with painless ulceration or gangrene without preceding claudication.
• ABI is unreliable due to medial calcification; use TBI <0.6 as threshold.
• Foot ulcers in diabetics are often of mixed ischaemic and neuropathic origin.
• Worse prognosis with higher amputation rates.
• Tight glycaemic control, meticulous foot care, podiatry referral are essential.
• Metformin must be withheld before iodinated contrast studies (CTA/DSA) due to risk of lactic acidosis.

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• A - Antiplatelet agents (aspirin or clopidogrel) + ACE inhibitors
• B - Blood pressure control (target <130/80)
• C - Cholesterol (statins - target LDL <1.8 mmol/L) + Cigarette cessation
• D - Diabetes control (HbA1c target ~7%) + Diet and exercise

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KEY IMAGES TO KNOW

• Aortoiliac bifurcation disease angiogram with collateralisation via lumbar and inferior mesenteric arteries

• Dependent rubor / "sunset foot" - elevation pallor, dependency rubor

• Dry gangrene of the toes in CLTI

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QUICK REFERENCE SUMMARY TABLE

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Structure Overview

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PG-Level High-Yield Points to Remember

• Fogarty catheter (1963) - Thomas Fogarty; first fem-pop bypass (1948) - Jean Kunlin; Seldinger technique (1953) - Sven-Ivar Seldinger
• Reperfusion injury >6 hrs = mandatory four-compartment fasciotomy consideration; compartment pressure >25 mmHg = fasciotomy
• COMPASS trial: Rivaroxaban 2.5 mg BD + aspirin reduces MALE + MACE in PAD
• CAPRIE trial: Clopidogrel > aspirin for secondary prevention in PAD
• Neointimal hyperplasia = predominant cause of intermediate graft/stent failure (1-24 months)
• Aortoenteric fistula = most dangerous late graft complication (herald bleed → exsanguination)
• WIFI score governs CLTI management (wound + ischaemia + foot infection must all be addressed)
• TBI <0.6 = significant arterial disease in diabetics when ABI is unreliable