Volume 15 Number 4 April 1992 Duplex scanning in renal artery fibromuscular disease 611

assume that the angiograms were ordered based on a positive duplex scan. So do we know basically if there were false-positive scans? Maybe you could give us a percentage on that.

Dr. Edwards. Depending on how you define the criteria for positive arteriograms, the sensitivity is always greater than 90%. The specificity ranges from 60% to 90%.

There has been only one false-positive scan to date, and that was in a patient in whom the angle was clearly miscalculated. We have since changed our methods to try to avoid that.

Dr. George Andros (Burbank, Calif.). Have you performed on-the-table duplex examinations immediately after the balloon angioplasty to tell the interventionist whether his endovascular procedure has been successful hemodynamically? Often the cosmetic appearance of the post-percutaneous transluminal angioplasty vessel may belie the tt'ue hemodynamic outcome so that assessment of .~nction would be useful. Of course, this linking of procedures might make for a long session on a hard table for the patient but it may also eliminate repeat percutane- ous transluminal angioplasty. In addition, it will allow you to classify as a residual rather than recurrent stenosis more precisely an outcome that later goes on to failure.

Dr. E&vards. We have not performed scans in the angiography suite, although that is a very interesting suggestion, and we might have to try that. It would be interesting to see; often we have to do multiple inflations to get what we consider a good technical result. It might be interesting to look at serial duplex measurements between balloon inflations. So far we have not done that. We will perform the scan that afternoon or the next morning, but we have not done it in the angiography suite itself.

Dr. Wesley S. Moore (Los Angeles, Calif.). It seems to me that in your presentation there are two elements. You are identifying patients before angiography, and, if I heard your presentation correctly, you are also identifying lesions that you think are hemodynamically significant and, therefore, should give a good result with intervention, irrespective of what their angiographic appearance might be.

Along that line, do you have any preliminary data on atherosclerotic lesions evaluated before either bypass or balloon angioplasty to determine what their hemodynamic significance is independent of the arteriographic ap- pearance?

Dr. Edwards. We have basically had similar data for the atherosclerotic lesions. Patients who respond to angio- plasty do have a reduction in the renal-aortic ratio, and the patients who have undergone bypass usually have normal- ization of the renal-aortic ratio.

Dr. Wesley S. Moore. Have you used the scan to t-urn patients down) Let us say, for example, you have a hypertensive patient. You identify the lesion. The patient undergoes angiography. The lesion on angiography looks like a 60% stenosis and yet perhaps the flow data or velocity data are such that you do not believe that this is a hemodynamically significant lesion. Have you turned patients down on that basis?

Dr. Edwards. No. Actually we have done just the opposite. There have been four patients I know of in whom the angiogram was borderline or thought to be less than 60%, but because of the duplex data the patients have been treated. All four of these patients have responded to treatment.

C O R R E C T I O N In the report entitled "Causes of primary graft failure after in situ saphenous vein bypass grafting", by Donaldson et al. (J VASC SURG 1992;1:113-20) the following reference cited in Table II was omitted from the reference citations. Sladen JG, Gilmour JL. Vein graft stenosis: characteristics and effect of treatment. Am J Surg 1981;141:549-53.