# 50 Ultrasound Unlocked

How to Perform and Interpret ABI, Segmental Pressures, and PVR: A Modern Clinical Guide

Noninvasive vascular testing remains the cornerstone of diagnosing peripheral artery disease (PAD). While the fundamentals of testing have not changed, the interpretation and clinical integration have evolved significantly.

The 2024 guideline from the American College of Cardiology and American Heart Association emphasizes a critical shift:

PAD diagnosis should rely on combined physiologic testing, not a single measurement.

This article walks through how to perform and interpret:

• ABI

• Segmental pressures

• Pulse volume recordings (PVR)

The Ankle-Brachial Index (ABI)

How to Perform ABI

The patient should be:

• Supine

• Rested for at least 10 minutes

Steps:

• Measure brachial pressures in both arms

• Measure ankle pressures using Doppler:

  • Posterior tibial (PT)

  • Dorsalis pedis (DP)

  • Use the highest ankle pressure

  • Divide by the highest brachial pressure

  Interpretation

  • 1.00–1.40 → Normal

  • 0.91–0.99 → Borderline

  • ≤0.90 → Peripheral artery disease

  • <0.50 → Severe disease

  • >1.40 → Non-compressible vessels

  

  Limitations of ABI

  Modern practice emphasizes that ABI can:

  • Be falsely elevated (calcification)

  • Be normal despite disease

  This is why:

  ABI must always be interpreted alongside waveform data

  Segmental Pressures

  How to Perform

  Cuffs are placed at:

  • High and low Thigh

  • Calf

  • Ankle

  • Trans-metatarsal

  Each level is measured using Doppler while:

  • Inflating above occlusion

  • Slowly deflating

  Interpretation

  Segmental pressures help identify where disease is located.

  Key Rules:

  • ≤20–30 mmHg change = normal

  • 30 mmHg drop = significant disease

  • 20 mmHg difference between legs = abnormal

    

  Localization Examples

  • Decreased thigh pressure → Aortoiliac disease

  • Drop from thigh to calf → Femoral disease

  • Drop from calf to ankle → Tibial disease

  Pulse Volume Recordings (PVR)

  How to Perform

  • Use same cuffs as segmental pressures

  • Inflate to ~65 mmHg

  • Record 3–4 cardiac cycles

  Normal Waveform

  A healthy waveform shows:

  • Rapid upstroke

  • Narrow peak

  • Dicrotic notch

  Abnormal Waveform

  As disease worsens:

  • Upstroke slows

  • Peak flattens

  • Dicrotic notch disappears

  • Amplitude decreases

  Why PVR Matters More Today

  PVR is increasingly important because it:

  • Reflects true blood flow

  • Is not affected by calcification

  • Helps confirm or refute ABI findings

  In modern vascular labs:

  Waveforms often carry more diagnostic weight than pressures alone

  Putting It All Together

  Modern Diagnostic Approach

  Instead of relying on one test, clinicians now integrate:

  • ABI → identifies disease

  • Segmental pressures → localize disease

  • PVR → confirms physiologic impact

  Clinical Example

  A patient presents with claudication:

  • ABI: 1.10 (normal)

  • PVR: dampened waveforms

  • Segmentals: mild gradient

  Interpretation:

  • Disease is present despite normal ABI

  • Additional testing is required

  My Key Takeaways

  • ABI remains essential—but not sufficient alone

  • Segmental pressures help localize disease

  • PVR provides the most reliable physiologic data

  My Final Thought

  The future of vascular diagnostics is not about replacing traditional tests - it’s about using them together more intelligently.

  Accurate diagnosis now depends on integration, not isolation