Intermittent bruit/thrill in access

Hello Dr. Agar,
I have a strange issue going on with my access. I have a graft which was installed August 25,2009. The graft starts at my anacube, goes up, and then loops around under my armpit, yes it is pretty long. It’s not a deep one. From time to time I notice no thrill/bruit, however when I fold my elbow I can get a weak thrill/bruit. This happens when I’m active like cleaning, etc. This also happens if I get very excited about something. However if I relax for a while all is strong again like it’s suppose to be. I asked my dialysis center about this and they said that that happens sometimes when doing activities. Is this indeed the truth that it is normal? I didn’t think one should ever lose there thrill. Also I did have my tech examine it and of course there’s not a problem. This problem is hard to pinpoint since it happens intermittently. On a dialysis run my access is very strong and gets good preassures and hardly never causes the machine to alarm, mostly when it does it’s because they’ve put the tape on too tight. Any ideas on the intermittent issue?

Dear Sullidog

I find myself at a bit of a loss to explain this odd behaviour of your graft … and by graft, I am assuming you mean a synthetic vessel. Usually, one might expect a rise in the systolic BP with excitation or exercise and this, physiologically, might then be expected to enhance flow rather than impede or lessen it …

Unless, possibly … and here I am really guessing from afar … your graft is developing a degree of inflow stenosis (a narrowing at the arterial end of the graft) which is, perversely, ‘protecting’ or ‘isolating’ the graft from the otherwise more active circulation that normally accompanies exercise such that the flow/thrill/bruit appears less, rather then more. By ‘protecting’ I really mean preventing the transmission of the more active circulation of exercise into the graft such that graft flow is, in relative terms, reduced.

Yours is a ‘youngish’ graft (only 5 months old) and right now is about the time when one might expect to begin to see some stenosis issues arising as the surgical site develops some circumferential fibrosis and possible some orificial shrinkage (a narrowing of the ‘orifice’ or ‘join’ between your native artery and the synthetic material used for the artificial graft).

That said … and, noting that, as you say, your dialysis is ‘uneventful’ and that you appear to have no pressure or flow issues … it would still be useful to know:

(1) your arterial pressure(commonly -80 to -100 in most fistulae) - to know if it is ‘more negative’ than it should be (like -120 t0 -150)… which might thus suggest that a bigger ‘suck’ is being exerted on the arterial flow that usual (again, signifying a potential arterial or ‘feed pressure’ stenosis)

(2) which alarm alarms when over-taped … the venous - or, my suspicion, the arterial?

(3) your transonic total fistula flow measurement (mls/min), assuming that you do have transonic measurements done? … but there again, dilution method flow parameters are sometimes not as reliable in grafts as in native fistulae, so this may not help much.

(4) when the alarms go off when it is ‘taped too tight’ … unusual in itself … is that only if the tape is placed too tight between the arteriail needle and the arterial anastamosis or does that apply at the venous end?

(4) what IS the arterial pressure (ie: minus what)?

Otherwise and these being all OK … then I am a bit at a loss to answer sensibly. But, as you say, it works OK and its’ good function is reassuring.

The only whisper of disquiet may be tha arterial anastamosis … and if this is narrowing, then there is the risk of thrombosis. Our view is that premeptive correction is always better than reactive repair - so it is worth just being sure all those numbers are OK and that arterial stenosis has been considered - and , hopefully, excluded.

Now - remember - most of that is just guess-work. It is difficult, without being able to play with, feel, touch, squidge and alround mess-with your graft to know. And, the explanations I have sought are simply trying to make some sense of an odd finding … though equally, my musings may be gobbledegook!

However, one thing I have (hopefully) learned is to listen carefully to what a patient says about their fistula. In my experience, a patient-sensed or patient-perceived change is commonly a real change. Such subtle changes are often first noted by an observant fistula-owner - well before we, as intermittent plunderers of the blood stream through the fistula, recognise any change.

So, if you have noted something odd - it does need to be thought about!

John Agar