I will take a shot at the differences first. A physiologic study i.e.:
segmental pressures, pulse volume recordings, and cw Doppler gives the
clinician an overview of the hemodynamics of the extremity.
The Doppler describes flow characteristics such as resistance and
pulsatility while the PVR records overall volume changes provided by
inflow from native vessels or collateral pathways. Segmental pressures
indicate the region of stenosis and/or occlusion. Just be careful to
remember that a proximal stenosis or occlusion will mask the presence or
severity of distal obstructions. Photoplethysmography even allows
evaluation of the digital circulation which is extremely important in
the diabetic patient.
Disease in the lower extremities tends to be categorized into either
inflow: the aortoiliac and common femoral segments. Outflow: the
superficial femoral and popliteal portions. Or runoff disease,
involving the tibial vessels. In the upper extremities physiologic
testing is also used for thoracic outlet disease, and cold sensitivity.
A duplex exam evaluates the anatomy much as an arteriogram does, by
direct visualization. It also allows differentiation of high grade
stenosis vs. occlusion. This can often be difficult with a physiologic
study yet very important in determining patient care, think stent as
opposed to graft. Duplex also allows evaluation of grafts, aneurysm, and
fistula more efficiently than a physiologic exam. Back in the old days
(before color flow) I used to dread lower arterial duplex studies but
with the technology available today the studies are much less time
Interpretation of duplex studies is also a little more cut and dried.
The severity of a stenosis is based on peak velocities in the stenosis
compared to the velocity in a normal segment of vessel just proximal to
the stenosis. This makes the technique widely applicable whether in
upper extremity, abdomen, or lower extremity.
I find that most labs lean towards one of the techniques based on their
preference or bias, however the two should be used to complement each
other not replace or substitute for one another.
As far as diagnostic criteria I recommend a good book, and there are
many out there, some including myself like Zwiebels' textbook for the
duplex side. If you can locate a copy there is an older reference by
Hershey, Sumner, and Barnes that explains the physiologic testing as
well as any I have ever seen. Bernstein has a current text available
that is very through as well.
Terry J Zwakenberg BS RVT RDCS (with emphasis on the BS ;-)
From: UVM Flownet [mailto:[log in to unmask]] On Behalf Of shawn
Subject: peripheral art duplex