Management of Abnormal Ankle-Brachial Index (ABI) Results
The management of a patient with an abnormal ABI result should follow a systematic approach based on the specific ABI value, with further diagnostic testing and appropriate interventions determined by the severity of peripheral artery disease (PAD) and associated symptoms.
Initial Assessment Based on ABI Value
- ABI results should be reported as abnormal (ABI ≤0.90), borderline (ABI 0.91–0.99), normal (1.00–1.40), or noncompressible (ABI >1.40) 1
- An abnormal ABI ≤0.90 confirms the diagnosis of PAD and requires further evaluation and management 1
- Borderline ABI (0.91-0.99) may indicate PAD and warrants exercise ABI testing if clinical suspicion is significant 1
- Noncompressible ABI (>1.40) indicates arterial calcification, commonly seen in patients with diabetes or chronic kidney disease, and requires alternative diagnostic methods 1
Follow-up Testing Based on Initial ABI Results
For Abnormal ABI (≤0.90):
- Segmental pressures with pulse volume recordings (PVR) and/or Doppler waveforms should be performed to localize anatomic segments of disease 1
- Exercise treadmill ABI testing can be useful to objectively assess functional status in patients with abnormal resting ABI 1
- Classify as asymptomatic PAD or chronic symptomatic PAD based on clinical presentation 1
For Borderline ABI (0.91-0.99):
- Exercise treadmill ABI testing is recommended to evaluate for PAD if clinical suspicion is significant 1
For Noncompressible ABI (>1.40):
- Toe-brachial index (TBI) with waveforms should be measured to diagnose PAD when ABI is >1.40 1
- A TBI ≤0.70 is considered abnormal and confirms the diagnosis of PAD 1
- Additional perfusion measures such as transcutaneous oxygen pressure (TcPO2) or skin perfusion pressure (SPP) can be useful in evaluating local perfusion 1
Management Based on Diagnostic Findings
For Asymptomatic PAD:
- Implement guideline-directed medical therapy (GDMT) and preventive foot care 1
- Initiate risk factor modification, including smoking cessation, diabetes management, blood pressure control, and lipid management 1, 2
- Consider antiplatelet therapy to reduce cardiovascular risk 1, 3
For Symptomatic PAD:
- Implement GDMT, preventive foot care, and structured exercise programs 1
- For patients with lifestyle-limiting claudication and inadequate response to GDMT and structured exercise, consider anatomic assessment for potential revascularization 1
- Imaging studies (duplex ultrasound, CTA, MRA, or invasive angiography) should be performed only when revascularization is being considered 1
For Chronic Limb-Threatening Ischemia (CLTI):
- Comprehensive vascular assessment including toe pressure/TBI with waveforms, TcPO2, and/or SPP to determine the likelihood of wound healing 1
- Anatomic imaging and revascularization planning should be considered 1, 2
- Interdisciplinary care team involvement is recommended 1, 3
Special Considerations
- Discordant ABI results (normal highest ABI but abnormal values in other ankle arteries) are associated with increased risk of cardiovascular events and should prompt more aggressive risk factor management 4, 5
- Patients with noncompressible ABIs have higher rates of mortality, major adverse cardiovascular events, and major amputation, requiring more intensive management 6
- Screening for abdominal aortic aneurysm with duplex ultrasound is reasonable in patients with symptomatic PAD 1
- Cost-effectiveness of ABI screening is most favorable in high-risk populations, such as tobacco users 7
Common Pitfalls to Avoid
- Relying solely on ABI in patients with diabetes or chronic kidney disease who may have noncompressible vessels 1, 3
- Performing invasive or noninvasive angiography for anatomic assessment in asymptomatic PAD patients 1
- Failing to recognize that nearly one-quarter of patients with CLTI may have normal ABIs, making it unreliable as the sole assessment tool 3
- Neglecting to perform ABI measurements both before and after peripheral vascular interventions to assess treatment efficacy 8