Peripheral Arterial Testing and Interpretation: Segmental Pressures, Waveforms, and PVR
Core Concepts
Peripheral arterial evaluation combines physiologic testing (ankle-brachial index, segmental pressures, pulse volume recordings, treadmill exercise) with duplex imaging. Know the ABI: highest ankle systolic pressure divided by the higher brachial pressure; normal ≥1.0, and values <0.9 suggest peripheral arterial disease. Understand that ABI can be falsely elevated in diabetes or renal disease due to medial calcinosis (non-compressible vessels), requiring toe-brachial index or PVR.
Waveforms and Segmental Interpretation
Recognize normal triphasic waveforms and how they dampen to biphasic and monophasic with proximal disease. Segmental pressure gradients localize disease: a drop between adjacent cuffs indicates a lesion in that segment. PVR amplitude and contour changes help when vessels are calcified. Duplex adds velocity criteria: focal velocity increase with spectral broadening indicates stenosis; post-stenotic turbulence and dampened distal flow confirm significance.
Traps
Common traps: relying on ABI alone when vessels are non-compressible; mislocalizing disease from a single pressure gradient without considering collateral flow; and interpreting exercise-induced symptoms without comparing pre- and post-exercise pressures. Another trap is confusing a normal resting ABI with absence of disease-exercise testing may unmask claudication.
Worked Example
A diabetic patient has an ABI of 1.3 and non-compressible ankle vessels. The trap is to call this normal. Instead, obtain a toe-brachial index (normal >0.7) or PVR; a low TBI confirms disease despite the high ABI. Always document waveform quality and cuff technique.
Rule of Thumb
If ABI >1.3 or vessels are non-compressible, switch to TBI or PVR. Localize disease by the segment with the largest pressure drop, and confirm with duplex velocity and waveform changes.