Which ABI value indicates ischemic rest pain?

• A. <0.50 multi-level disease or long segment occlusion
• B. <0.80 probable claudication
• C. <0.30 ischemic rest pain
• D. <0.95 abnormal

Answer: (C)

Ischemic rest pain appears when blood flow to the legs is severely reduced and tissues cannot meet resting metabolic needs. The ankle-brachial index (ABI) measures perfusion by comparing ankle and arm pressures; the lower the ABI, the more severe the arterial insufficiency. An ABI of about 0.30 or lower is strongly associated with ischemic rest pain, reflecting critical limb ischemia. At this level, blood supply is insufficient even at rest, often causing burning or aching pain in the toes or feet that worsens at night when lying down.

Values that indicate substantial PAD but primarily predict claudication tend to be higher, suggesting pain with activity rather than pain at rest. An ABI near normal (around 0.95 or higher) is not consistent with rest pain, and a threshold around 0.50 is more aligned with extensive disease rather than specifically signaling rest pain. Hence, the value most indicative of ischemic rest pain is the very low ABI, around 0.30 or less.