What's the next step for a diabetic (DM) patient with intermittent claudication and a borderline Ankle-Brachial Index (ABI) result of 0.96?

Exercise ABI Testing is the Next Step for Diabetic Patient with Intermittent Claudication and Borderline ABI of 0.96

For a diabetic patient with intermittent claudication and a borderline ABI of 0.96, exercise ABI testing (before and after exercise) is the recommended next step to improve diagnostic accuracy and confirm the presence of peripheral arterial disease (PAD).

Rationale for Exercise ABI Testing

Understanding Borderline ABI Results

• An ABI of 0.96 falls within the borderline range (0.91-1.00) according to the 2019 ESC guidelines 1
• In patients with diabetes, standard ABI measurements may have reduced sensitivity due to:
  • Medial arterial calcification common in diabetes 1, 2
  • Potential false-negative results with resting ABI 3

Diagnostic Algorithm for Borderline ABI

1. When symptoms suggest PAD (like intermittent claudication) but the resting ABI is normal or borderline:

   • Sensitivity can be improved by post-exercise ABI testing 1
   • Exercise testing can unmask moderate arterial stenosis not detected at rest 1

2. The ESC guidelines specifically state: "If symptoms suggest LEAD but the ABI result is normal, sensitivity can be improved by post-exercise ABI or the toe brachial index (TBI) at rest" 1

How to Perform Exercise ABI Testing

• Use a standardized treadmill protocol (typically Strandness protocol at 3 km/h and 10% slope) 1
• Measure ABI before exercise as baseline
• Have patient walk until claudication pain occurs or they cannot continue
• Measure ABI immediately after exercise
• A post-exercise ankle systolic blood pressure decrease >30 mmHg or a post-exercise ABI decrease >20% is diagnostic for PAD 1

Clinical Significance of Exercise Testing

• Exercise testing provides objective functional assessment 1

• It helps determine maximal walking distance, which is valuable for:

  • Quantifying functional limitation
  • Establishing baseline for monitoring treatment response
  • Guiding treatment decisions 1

• In diabetic patients with claudication, exercise testing is particularly valuable as:

  • Diabetic patients have significantly lower Walking Impairment Questionnaire scores 4
  • They have poorer quality of life compared to non-diabetic claudicants 4

Alternative or Additional Tests to Consider

If exercise testing is not feasible or results remain inconclusive:

1. Toe-Brachial Index (TBI): Particularly useful in diabetic patients as medial calcification rarely affects digital arteries 1

   • A TBI <0.70 is diagnostic for PAD 1

2. Duplex Ultrasound: Provides anatomical and hemodynamic information 1

   • 85-90% sensitivity for detecting significant lesions
   • Can help identify location and severity of stenosis

Management Implications

Based on diagnostic findings, treatment options include:

• Supervised exercise training: 30-45 minutes, at least 3 times weekly for 12+ weeks 1
• Pharmacotherapy: Consider cilostazol 100 mg twice daily (if no heart failure) 1, 5
• Antiplatelet therapy: Aspirin 75-325 mg daily or clopidogrel 75 mg daily 1
• Risk factor modification: Smoking cessation, lipid management, diabetes control 1

Conclusion

Exercise ABI testing is the most appropriate next step for this diabetic patient with intermittent claudication and borderline ABI. This approach will help confirm the diagnosis of PAD, quantify functional limitation, and guide appropriate treatment decisions to improve symptoms and reduce cardiovascular risk.