What does a triphasic waveform in an Ankle-Brachial Index (ABI) test indicate?

Triphasic Waveform in Ankle-Brachial Index (ABI) Test

A triphasic Doppler arterial waveform at the ankle during an ABI test strongly indicates the absence of peripheral artery disease (PAD) and represents normal arterial blood flow. 1

What is a Triphasic Waveform?

A triphasic waveform represents normal arterial blood flow and has three distinct components:

• Forward flow during systole (first phase) 1
• Brief flow reversal during early diastole (second phase) 1
• Forward flow during late diastole (third phase) 1

Clinical Significance of Triphasic Waveforms

Normal Arterial Status

• The presence of triphasic pedal Doppler arterial waveforms is one of the tests that largely excludes PAD 1
• Triphasic waveforms indicate healthy, elastic arterial walls with normal compliance 1
• In clinical practice, triphasic waveforms are considered a reliable indicator of normal arterial flow even when other measurements may be ambiguous 1

Diagnostic Value

• Triphasic waveforms provide stronger evidence for the absence of PAD than some other measurements 1
• When combined with normal ABI values (0.9-1.3), triphasic waveforms significantly increase confidence in ruling out PAD 1
• The presence of triphasic waveforms was used as a criterion for control subjects in studies evaluating PAD diagnostic methods 1

Relationship to ABI Values

• Normal ABI values (1.00-1.40) with triphasic waveforms strongly indicate absence of significant arterial disease 1
• Even when ABI values are borderline (0.91-0.99), the presence of triphasic waveforms suggests normal arterial flow 1
• Doppler waveform analysis can be particularly valuable when ABI results are inconclusive or potentially misleading 2

Clinical Applications

Screening and Diagnosis

• Doppler waveform analysis, including identification of triphasic patterns, is recommended as part of the initial assessment for PAD 1
• The combination of ABI measurement with Doppler waveform assessment improves diagnostic accuracy 1
• Waveform analysis is especially valuable in patients with diabetes or chronic kidney disease who may have falsely elevated ABI due to arterial calcification 2, 3

Advantages Over ABI Alone

• Waveform analysis can detect PAD even when ABI values are falsely normal due to arterial calcification 2
• Triphasic waveforms provide qualitative information about arterial flow that complements the quantitative data from pressure measurements 1
• Waveform analysis is less affected by arterial calcification than pressure-based measurements 2, 3

Limitations and Considerations

• Operator skill and experience can affect the accuracy of waveform interpretation 4
• Waveform analysis should be considered alongside other clinical findings and tests 1
• In patients with suspected PAD despite normal waveforms, additional testing may be warranted 1, 5

Practical Implications

• When triphasic waveforms are present, clinicians can be reasonably confident in excluding significant PAD 1
• In patients with exertional leg symptoms but triphasic waveforms, alternative diagnoses should be considered 1
• Regular vascular assessment, including waveform analysis, is recommended for high-risk patients even when initial findings are normal 1, 6

In summary, triphasic waveforms in an ABI test represent a normal finding that strongly suggests the absence of peripheral artery disease. This finding is particularly valuable when combined with normal ABI values and can help guide clinical decision-making regarding the need for further diagnostic testing or intervention.