Discussion

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Dr William Bogey (Greenville, NC). I would like to thank the association for the opportunity to discuss this paper, and Dr. Pearce and colleagues for providing me with a copy of the manuscript in a timely fashion. The Wake Forest group, under the leadership of our current president, is well known for their expertise in the open operative management of renovascular disease. This paper discusses their experience with endovascular treatment of this disease process, and, as we've come to expect, they have done an excellent job.

Early results were examined, and at a median of approximately 9weeks post procedure, statistically significant decreases in mean systolic and diastolic BP as well as number of antihypertensive meds were observed. When looked at categorically, however, only approximately 22% had their hypertension helped, and 28% had their renal insufficiency improved, while about 7% experienced a worsening of renal function.

In reviewing this manuscript, a number of questions entered my mind. I must confess, however, that many of these questions were answered in the discussion section of the manuscript, and I had to strike them from my list. Of course, I do still have a couple of questions remaining. First, you note that previous experience led you to the technical approach used. Can you enlighten us as to the specifics of this technique? In particular, you feel that distal protection is of value. My bias has been that the majority of embolic debris that may damage the kidney is generated during the process of gaining access to the artery, and thus by the time the distal protection device has been deployed, the cat may well be out of the bag. Do you feel differently, or does your technique allow you to minimize this risk?

Secondly, you note that the results obtained here are better when “complete” treatment is done, yet you also state that it is not uncommon to perform only partial treatment in your current algorithm. Will the results of this study cause you to alter this algorithm?

Finally, you note that the magnitude of improvement following percutaneous treatment is significantly less than that seen after open therapy and you suggest that the trade-off in results versus morbidity may be acceptable. My question is why is the magnitude of improvement so much less? My admittedly naïve understanding leads me to think that an open artery by any technique should give a similar result, so why are the outcomes so dramatically different. This study is only looking at short-term response, not the long-term outcome that one might expect to favor surgery, eliminating the bias improved long term durability might provide. It doesn't appear to me that it can all be explained by the lack of complete treatment in the 21% in this study. Do you have any insight as to why this may be? Is it continued microembolism from the diseased aorta or renal artery, or perhaps the damage caused by the debris that gets generated before the protection device is in place? Is it that you are actually getting a less “complete” repair than your ultrasound data would suggest, or is it perhaps some other factor? Has the decreased morbidity caused you to expand your indications to include patients who would not have met your open repair indications? I would appreciate your thoughts on this, as the magnitude of the difference in response between open and endovascular repair shown by your group is indeed sobering.

Once again, I think the association for this opportunity, and I look forward to hearing your response.

Dr. Pearce. Your first question involves the technical aspects of distal embolic protection and why we continue to employ distal protection. A paper presented last year at this meeting by Dr. Corriere, categorized our embolic data from this procedure and very nicely demonstrated the large amount of debris liberated by angioplasty and stenting. Indeed you are correct that the previous ex-vivo data demonstrated that just passing the guide wire results in a large amount of embolic debris. We feel there is additional benefit for catching the embolic debris that occurs with the angioplasty procedure itself.

Why are we still doing staged repair vs. complete intervention? Our treatment algorithm involves treating patients with bilateral disease in a unilateral fashion and then reassessing their response including blood pressure control, hypertension medications utilized, as well as renal function response. If the patient has an adequate renal function and blood pressure response, we will continue to maximize the medical management of atherosclerotic risk factors and defer further intervention for observation. You referred to the additional data and figure included in the paper. I did not present that here because it confuses the issue a little. The unadjusted results of the group as a whole suggested that patients with bilateral disease undergoing bilateral repair favored better than those undergoing unilateral repair. Unilateral repair of bilateral disease was not common in this patient group and the results in the figure are not adjusted for preoperative values. Moreover, when a multivariable regression analysis was performed we did not observe the same renal function benefits with complete vs. incomplete repair.

Your final question inquires as to why the results here less favorable than those observed in our open repair experience? I think that there are a number of factors that can play into that observation, but this paper was not designed to provide a direct comparison between open and percutaneous results. However, when we compared the demographics of the patients in the percutaneous group to the demographics of the open group, we had more diabetics in the percutaneous group. Additionally, the percutaneous patients tended to be older by at least five years with less renal insufficiency compared to the open group. Finally, I think you have correctly mentioned additional factors that could also be in play for the discrepancies in renal function response observed which include the recognized residual disease and the effects of embolization.