Correspondence
Treatment of Ostial Renal-Artery Stenoses with Vascular Endoprostheses
N Engl J Med 1997; 337:132-133July 10, 1997
- Article
To the Editor:
Regarding the treatment of renal-artery stenoses with endoprostheses, Blum et al. (Feb. 13 issue)1 mention as primary outcomes in their patients that 16 percent had long-term normalization of their blood pressure and 84 percent were free of primary occlusion of the stent 60 months after stent placement. From the article it is clear that 16 patients were not followed for three months. Therefore, the measurement of blood pressure used to assess the effect of treatment must have been the blood pressure measured at discharge. Taking this blood pressure to represent the result of treatment is not in accordance with the conventional way of assessing changes in blood pressure after the relief of renal-artery stenosis, as set forth in the Cooperative Study of Renovascular Hypertension,2 which is considered to contain the state-of-the-art criteria. One of these criteria is that a period of one year should elapse before the effect on blood pressure is determined.2 The findings of Blum et al. must therefore be seen as premature.
A second point concerns the rate of restenosis. Because 16 patients were not followed for three months, it is unclear whether or not they had restenosis, because the first follow-up study took place at three months, when a duplex ultrasound examination was performed. From the results presented, it can be gathered that the maximal sensitivity of the authors' method of duplex ultrasonography is 73 percent. The reported sensitivities of the methods used by Blum et al. are similar to those in the literature or even lower.3,4 Duplex ultrasonography, therefore, gives no proof that restenosis is absent. Accordingly, the rate of restenosis should be calculated on the basis of the gold standard — in this case, patients in whom control angiography is performed. These are the 47 patients with one year of follow-up and the 27 patients with two. When this standard is applied, the restenosis rate is 10 of 47 at one year (21 percent) and 11 of 27 at two years (41 percent). For the 16 patients who were followed for more than two years, no control angiographies are described, and thus the status of the stents in these patients must be viewed as uncertain. When angiography is used as the final measure of restenosis, the results of Blum et al. do not differ much from those in other recently published series.5
5 ReferencesCornelis T. Postma, M.D., Ph.D.
Theo Thien, M.D., Ph.D.
University Hospital Nijmegen, 6500 HB Nijmegen, the Netherlands1
Blum U ,Krumme B ,Flugel P , et al. Treatment of ostial renal-artery stenoses with vascular endoprostheses after unsuccessful balloon angioplasty. N Engl J Med 1997;336:459-465
Full Text | Web of Science | Medline2
Maxwell MH ,Bleifer KH ,Franklin SS ,Varady PD . Cooperative Study of Renovascular Hypertension: demographic analysis of the study. JAMA 1972;220:1195-1204
CrossRef | Web of Science | Medline3
Bude RO ,Rubin JM . Detection of renal artery stenosis with Doppler sonography: it is more complicated than originally thought. Radiology 1995;196:612-613
Web of Science | Medline4
Burdick L ,Airoldi F ,Marana I , et al. Superiority of acceleration and acceleration time over pulsatility and resistance indices as screening tests for renal artery stenosis. J Hypertens 1996;14:1229-1235
CrossRef | Web of Science | Medline5
Baert AL . Renal artery stent placement. Radiology 1994;191:619-621
Web of Science | Medline
Author/Editor Response
The authors reply:
To the Editor: Drs. Postma and Thien address the effect of renal-artery stenting on blood pressure in our patients. They state that the follow-up period was too short to allow the effect on blood pressure to be assessed, and they therefore consider our results premature. We did not use the 1972 criteria they cite1 but instead used the criteria developed by the Standards of Practice Committee of the Society of Cardiovascular and Interventional Radiology2 to evaluate clinical success. In accordance with these standards, we have found that the normalization of blood pressure in 16 percent of our patients at the time of discharge has been maintained in all patients during a follow-up period now lasting 12 months. We therefore do not agree with the statement that the effect of renal-artery stenting on blood pressure was only transient.
With regard to the rate of restenosis, duplex sonography was performed in all 68 patients at three months. It demonstrated restenosis of more than 50 percent in only two patients, which was confirmed angiographically. Restenoses detected by duplex sonography at 6, 12, and 24 months of follow-up were also confirmed by angiography. At present, the mean follow-up period for the study group is 39 months (range, 15 to 96), with angiographically confirmed control in 69 renal arteries at 12 months. In each case, angiography confirmed the results of duplex sonography. We agree that the sensitivity of duplex sonography in the detection of renal-artery stenosis is low when only the main renal artery is evaluated and only peak systolic velocity is successfully measured.3 However, the combination of extrarenal and intrarenal scanning with the assessment of peak and end-diastolic flow velocity and the side-to-side comparison of the intrarenal resistive index has a much higher sensitivity and represents, in our view, the method of choice when color duplex sonography is available for the diagnosis of renal-artery stenosis. In an angiographically controlled study performed with the combined analysis, we achieved sensitivity and specificity rates of 89 and 92 percent, respectively.4 In the current study of a highly selected population, all of whom had renal-artery stenosis, the sensitivity was 100 percent, confirming the findings of Olin et al.5 Finally, to calculate the rate of restenosis, we used the Kaplan–Meier method to estimate the cumulative primary and secondary occlusion-free survival rates after stent placement.
5 ReferencesUlrich Blum, M.D.
Bernd Krumme, M.D.
University Hospital Freiburg, D-79106 Freiburg, Germany1
Maxwell MH ,Bleifer KH ,Franklin SS ,Varady PD . Cooperative Study of Renovascular Hypertension: demographic analysis of the study. JAMA 1972;220:1195-1204
CrossRef | Web of Science | Medline2
Standards of Practice Committee of the Society of Cardiovascular and Interventional Radiology
Web of Science | Medline3
Postma CT ,van Aalen J ,de Boo T ,Rosenbusch G ,Thien T . Doppler ultrasound scanning in the detection of renal artery stenosis in hypertensive patients. Br J Radiol 1992;65:867-870
CrossRef4
Krumme B ,Blum U ,Schwertfeger E , et al. Diagnosis of renovascular disease by intra- and extrarenal Doppler scanning. Kidney Int 1996;50:1288-1292
CrossRef | Web of Science | Medline5
Olin JW ,Piedmonte MR ,Young JR ,DeAnna S ,Grubb M ,Childs MB . The utility of duplex ultrasound scanning of the renal arteries for diagnosing significant renal artery stenosis. Ann Intern Med 1995;122:833-838
Web of Science | Medline
