Why is it important to ask for pulsatility and pedal artery acceleration time when performing Peripheral Vascular Laboratory (PVL) testing for Peripheral Artery Disease (PAD)?

Importance of Pulsatility and Pedal Artery Acceleration Time in PVL for PAD

When performing Peripheral Vascular Laboratory (PVL) testing for Peripheral Artery Disease (PAD), assessment of pulsatility and pedal artery acceleration time (PAT) is crucial because these measurements provide critical hemodynamic information that the ankle-brachial index (ABI) alone cannot detect, especially in patients with chronic limb-threatening ischemia (CLTI) where ABI may be falsely normal or elevated.

Limitations of ABI Alone

• ABI alone is inadequate for assessing patients with suspected CLTI 1
• Nearly 25% of patients with CLTI may have ABI values between 0.90-1.40 (normal range) 1
• 29% of patients with CLTI have an ABI between 0.70-1.40 1
• Poor concordance exists between ABI and toe pressure/TBI among CLTI patients, with only 58% of patients with abnormal toe pressures showing abnormal ABIs 1

Value of Pulsatility Assessment

Pulsatility assessment via Doppler waveform analysis provides critical information:

• Abnormal continuous-wave Doppler waveforms from the base of the great toe can support PAD diagnosis when ABI is inconclusive 1
• Triphasic pedal Doppler arterial waveforms strongly indicate absence of PAD 1
• Waveform analysis helps detect PAD even when calcified arteries cause falsely elevated ABI readings 1
• Pulsatility index (PI) can be used to normalize blood flow measurements, resulting in more accurate and stable measurements of clinical significance 2

Importance of Pedal Artery Acceleration Time (PAT)

PAT offers significant diagnostic and prognostic value:

• PAT has been correlated with ABI and clinical presentation of PAD 1
• Improvement in PAT (≤180 ms) after revascularization in CLTI patients is associated with limb salvage 1
• PAT has acceptable diagnostic accuracy as an assessment tool for PAD, with AUC of 0.79 (0.74-0.85) 3
• PAT diagnostic threshold for PAD presence may be optimized at >85 ms 3
• PAT measurements yield similar accuracy to toe pressure and TBI measurements 3

Clinical Algorithm for PVL Assessment in PAD

1. Initial Assessment:

   • Perform ABI measurement as baseline test
   • Assess pulsatility with Doppler waveform analysis

2. When ABI is Normal (0.90-1.40) but PAD is Still Suspected:

   • Evaluate pulsatility patterns (monophasic, biphasic, triphasic)
   • Measure PAT (abnormal if >85 ms)
   • Consider toe-brachial index (TBI) if available (abnormal if <0.70)

3. For Patients with Suspected CLTI:

   • Always include pulsatility assessment and PAT measurement
   • Supplement with toe pressure/TBI with waveforms
   • Consider transcutaneous oxygen pressure (TcPO₂) and skin perfusion pressure (SPP)

4. Interpretation Guidelines:

   • Triphasic waveforms generally exclude significant PAD
   • Monophasic waveforms suggest significant stenosis
   • PAT >180 ms indicates severe PAD
   • Improvement in PAT after intervention correlates with better outcomes

Common Pitfalls to Avoid

• Relying solely on ABI in patients with diabetes or renal disease who may have calcified, non-compressible arteries
• Failing to assess pulsatility when ABI is normal but clinical suspicion for PAD remains high
• Not considering PAT as a valuable adjunctive measure, especially in patients with CLTI
• Performing vascular testing in cold rooms, which can cause arterial vasoconstriction and affect results 1

By incorporating both pulsatility assessment and PAT measurement into PVL testing for PAD, clinicians can achieve more accurate diagnosis, better assess disease severity, determine revascularization strategy, and predict outcomes after intervention, ultimately improving patient care and reducing limb loss.