Applications
PPG for Peripheral Artery Disease (PAD) Assessment
PPG provides non-invasive assessment of peripheral artery disease through waveform morphology analysis at multiple limb sites. Characteristic PAD signatures include monophasic or dampened waveforms, absent dicrotic notch, prolonged systolic upstroke time, and severely reduced ankle perfusion index, all reflecting impaired distal arterial flow from stenotic lesions.
How it works
Schematic summary of this guide. Waveforms are illustrative, not measured data.
PPG complements ABI assessment through waveform morphology analysis at the toe, ankle, and forefoot — particularly valuable for calcified vessels where ABI is falsely normal. Normal triphasic PPG waveforms (systolic forward flow, early diastolic reversal, late diastolic forward flow) at the ankle become biphasic in moderate PAD and monophasic in severe disease, providing a qualitative severity assessment that correlates with angiographic stenosis degree.
Pulse arrival time delay between upper and lower extremity PPG sites quantifies the additional pulse travel time through diseased arterial segments and correlates with stenosis severity.
Digital volume pulse (DVP) analysis using finger PPG provides systemic arterial stiffness indices that serve as PAD risk markers even before symptomatic disease develops. The stiffness index (body height / delay between systolic and diastolic peaks) and reflection index (diastolic peak / systolic peak) are independently associated with carotid atherosclerosis and PAD risk factors in population studies.
Frequently Asked Questions
Can PPG replace ankle-brachial index for PAD screening?
PPG waveform analysis is complementary to ABI, not a replacement. PPG excels when ABI is non-compressible (calcified vessels in diabetes/renal disease).
What are normal vs. abnormal PPG waveform features at the ankle?
Normal ankle PPG shows triphasic waveform with prominent diastolic notch and secondary diastolic wave. Moderate PAD shows biphasic (absent diastolic reversal). Severe PAD shows monophasic rounded waveform with absent notch and prolonged systolic upstroke time.
Does PPG detect critical limb ischemia?
In critical limb ischemia (CLI), digital PPG may show flat-line or barely detectable pulsations. PPG cannot quantify tissue perfusion adequacy for wound healing prediction — transcutaneous oximetry (TcPO2) is preferred for that purpose.