In a patient experiencing ischemic rest pain, what is the likely ankle/arm systolic pressure ratio?

When a patient is experiencing ischemic rest pain, it typically indicates a severe reduction in blood flow to the lower extremities, often due to critical limb ischemia. In this condition, the ankle/arm systolic pressure ratio is a crucial measure used to assess the severity of the ischemia.

A ratio of less than 0.50 suggests that the blood flow to the ankle is severely compromised compared to that of the arm, which reflects significant arterial blockage. This finding correlates with the presence of ischemic rest pain, as lower peripheral pressures indicate that the blood supply is inadequate to meet the metabolic demands of the tissues, leading to pain even at rest.

In contrast, ratios that are higher—such as those between 0.50 and 0.75, or greater than 0.75—would suggest less severe ischemia or even normal perfusion, which would not be consistent with the presence of ischemic rest pain. The approximate threshold of 0.80 does not correspond to the critical condition associated with ischemic symptoms.