What is the interpretation and management for a patient with ABI results indicating moderate arterial occlusive disease in one leg and no significant disease in the other?

Interpretation and Management of Asymmetric Ankle-Brachial Index Results

The right leg ABI of 0.97 indicates borderline perfusion, while the left leg ABI of 0.79 indicates moderate arterial occlusive disease requiring cardiovascular risk assessment and management. This asymmetric finding is clinically significant and warrants attention to both limbs individually.

Understanding Your ABI Results

Right Leg (ABI 0.97):

• Classification: Borderline (0.91-0.99)
• Interpretation: While not meeting the strict criteria for PAD (≤0.90), borderline values should not be dismissed 1, 2
• Waveform findings: Multiphasic waveforms at both posterior tibial and dorsalis pedis arteries suggest preserved flow dynamics
• Digit pressure: "Borderline healing" indicates potential perfusion concerns

Left Leg (ABI 0.79):

• Classification: Abnormal - moderate arterial occlusive disease (0.60-0.89) 1
• Interpretation: Definitive evidence of PAD requiring intervention
• Waveform findings: Despite the reduced ABI, multiphasic waveforms suggest the disease may be proximal to measurement sites
• Digit pressure: "Borderline healing" indicates potential perfusion concerns

Clinical Significance

1. Cardiovascular Risk Assessment:

   • An ABI <0.90 approximately doubles your risk of myocardial infarction and cardiovascular death 2
   • The presence of PAD in one limb warrants comprehensive cardiovascular risk assessment 1

2. Diagnostic Considerations:

   • Using the lower ABI of the two legs (0.79) is recommended for cardiovascular risk assessment 1
   • The American Heart Association notes that using only the higher ABI may miss significant disease 1
   • Multiphasic waveforms with reduced ABI suggest proximal disease rather than distal small vessel disease

3. Healing Potential:

   • "Borderline healing" digit pressures in both feet require attention
   • Absolute pressures may correlate better with healing potential than ABI ratios alone 3

Management Recommendations

Immediate Steps:

1. Initiate Guideline-Directed Medical Therapy:

   • Antiplatelet therapy (aspirin or clopidogrel)
   • High-intensity statin therapy
   • Blood pressure control (target <130/80 mmHg)
   • Diabetes management if applicable
   • Smoking cessation if applicable

2. Vascular Specialist Referral:

   • Consultation is warranted for moderate arterial disease (ABI 0.79) 1
   • Consider exercise ABI testing for the right leg (borderline ABI 0.97) to unmask potential claudication 4

3. Additional Testing to Consider:

   • Exercise ABI testing may reveal functional limitations not apparent at rest
   • Duplex ultrasound to locate and quantify stenotic lesions 1
   • Consider toe-brachial index if there are concerns about arterial calcification, especially if diabetes is present 5, 6

Long-term Management:

• Structured exercise program (supervised if available)
• Regular foot examinations and meticulous foot care
• Annual ABI monitoring to assess disease progression
• Aggressive management of all cardiovascular risk factors

Important Caveats

• The presence of multiphasic waveforms with reduced ABI is somewhat discordant and may indicate proximal disease
• Borderline digit pressures in both feet require close monitoring regardless of ABI values
• If diabetes is present, be aware that ABI may underestimate disease severity due to arterial calcification 5, 6
• Consider absolute pressures in addition to ABI when evaluating healing potential 3

This asymmetric finding (normal right ABI, abnormal left ABI) is not uncommon and emphasizes the importance of evaluating each limb independently while recognizing the systemic implications of peripheral arterial disease.