Subject: Re: Intra operative vein bypass graft duplex
Author:  [log in to unmask] at Internet
Date:    7/17/96 8:03 AM

Colleagues;

How does ones one evaluate the elevated velocities which inevitably occur at the
distal anastomosis as large vein is attached to smaller native vessel? This 
seems to be a problem particularly with distal bypasses i.e. fem- DP or fem PTA.

Terry Case
University of Vermont

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I know, I know, I've been preaching this stuff for years but here goes again. Is
there a stenosis associated with the flow acceleration? Is a 1.5 mm residual 
lumen at the distal end of a 4 mm vein a stenosis at all if the recipient vessel
is 1.5 mm?? Well, yes and no!! I suppose you could argue either way. What they 
try to do here is make a long spatulated anastomosis and make it a smooth 
transition. If we don't visualize a stenosis intra-operatively, then they would 
likely not try to revise it regardless of the velocities. Remember, velocities 
may be greatly affected by hyperemia, spasm, etc. Remember Holec's Second Law of
Doppler - A Doppler change is only a Doppler change, it may be a flow change if 
you interpret the information correctly, and it may or may not be a stenosis. 
All Doppler changes must be explained by imaging! (Holec's First Law of Vascular
Imaging!)

In other words Terry, expect that velocity change anywhere you see a dramatic 
caliber change. But no hard numbers from here. In our experience, the 
variability is high. It varies with C.O., inflow, graft quality and mostly what 
the recipient vessel is like. Many of these are calcified, stiff, and diseased. 
Also remember Smith's First Law of Surgery -  Perfect is often the enemy of 
good! Very often a tough call.

Bill Schroedter
Bon Secours Venice Hospital 
Vascular Lab
Venice,Fl.