Is chronic total occlusion of arteries classified as Peripheral Artery Disease (PAD) or Chronic Limb-Threatening Ischemia (CLTI)?

Chronic Total Occlusion: PAD or CLTI Classification

Chronic total occlusion of arteries is classified as peripheral artery disease (PAD), but whether it constitutes chronic limb-threatening ischemia (CLTI) depends entirely on the clinical presentation—specifically the presence of ischemic rest pain, non-healing ulcers ≥2 weeks duration, or gangrene. 1, 2

Understanding the Relationship

CLTI is a specific clinical syndrome within the broader spectrum of PAD, not a separate entity. The presence of arterial occlusion alone does not define CLTI. 3

PAD Classification

• Chronic total occlusion represents anatomic disease within the PAD spectrum 3
• PAD exists on a continuum from asymptomatic disease to intermittent claudication to CLTI 1
• The anatomic finding of total occlusion requires clinical correlation to determine disease severity 3

CLTI Diagnostic Criteria (Must Have Clinical Manifestations)

CLTI requires BOTH arterial occlusive disease AND one of the following clinical features: 1, 2

• Ischemic rest pain in the forefoot with confirmed hemodynamic compromise (ABI <0.40, ankle pressure <50 mmHg, toe pressure <30 mmHg, or TcPO2 <30 mmHg) 3
• Non-healing lower limb ulceration lasting ≥2 weeks 3, 1
• Gangrene involving any portion of the foot or lower limb 3, 1
• Diabetic foot ulcer in the setting of PAD 3

Critical Distinction

The key pitfall is assuming that severe anatomic disease (like chronic total occlusion) automatically equals CLTI. 3 Some patients maintain limb viability for extended periods despite total occlusions through collateral circulation, while others with less severe anatomic disease may develop CLTI due to diabetes, infection, or wounds. 3

Why This Matters Clinically

• CLTI is not defined by ankle or toe pressures alone because amputation risk depends on the presence of wounds and infection, not just ischemia severity 3
• 50-70% of CLTI patients have diabetes, often presenting as neuro-ischemic diabetic foot ulcers where patients may have severe tissue loss without pain due to neuropathy 3, 2
• The WIfI classification system (Wound, Ischemia, foot Infection) should be used to stratify CLTI severity, grading each component from 0-3 3, 1

Clinical Algorithm for Classification

When encountering chronic total occlusion: 1, 2

1. Confirm PAD diagnosis with objective testing (ABI, imaging showing occlusion) 3
2. Assess for CLTI criteria:
   • Is there ischemic rest pain? 3, 1
   • Are there non-healing ulcers >2 weeks? 3, 1
   • Is there gangrene present? 3, 1
   • If diabetic, are there foot ulcers? 3
3. If YES to any above: Classify as CLTI and apply WIfI staging 3, 1
4. If NO to all above: Classify as PAD (may be asymptomatic or claudication depending on symptoms) 3

Management Implications

CLTI patients require urgent vascular team evaluation (vascular physician, surgeon, radiologist) with consideration for revascularization to restore inline blood flow to the foot, whereas PAD without CLTI may be managed with medical therapy and supervised exercise. 1 The 30-day mortality after major amputation in CLTI reaches 22%, emphasizing the urgency of proper classification. 1