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Gianturco Z Stents for Hemodialysis Grafts
Letters
Gianturco Z Stents for Hemodialysis Grafts From: Sumit Roy, MBBS, MD Institute for Surgical Research, Rikshospitalet Pilestredet 32 N-0027 Oslo, Norway. Editor: A small error seems to have crept into the excellent paper by Trerotola et al on the comparative evaluation of stents in hemodialysis grafts (1). The authors suggest that the Gianturco-Rosch stent may be preferable to the Gianturco Z stent for hemodialysis grafts. As the subunits in the former are held together by suture, it is postulated that the problem of fractures of soldered joints causing stent migration will be eliminated. Selection of the Gianturco-Rosch device may in fact simply substitute one drawback with another. The severe inflammatory response noticed by the authors near the soldered joints would probably be exaggerated with the Gianturco-Rosch model. Unlike the Gianturco Z stent, the Rosch-modified version is soldered proximal to every bend in the wire to create an "eyelet," and thus is likely to produce five to six times as many foci of intimal inflammation as the former. The observations of Trerotola et al bring into question the advisability of using solder in the fabrication of this family ofstents. Not only is an alloy of uncertain biocompatibility used (1,2), but soldering is an inappropriate method for bonding stainless steel (3). A completely solder-free Z stent is not just a theoretical possibility (4) and has been successfully used in the urethra (5), the venous. system (6), and the biliary tract (Baijal et aI, unpubhshed data, 1994). The amount of solder on the Gianturco-Rosch stents can also be substantially reduced by eliminating the soldering of adjacent limbs near the be?-ds to cre~te the "eyelets." Though visually pleasing, thIS feature IS superfluous, contributing nothing to the configurational stability of the stent. From benchtop (Roy et aI, unpublished data, 1992) and clinical experience (6) it is evident that the configuration of the wire at this sit~ itself ensures that the suture loop does not migrate and the entire ensemble does not telescope during backloading into the delivery sheath. The results presented by the authors suggest that despite its simple design, the Gianturco Z stent may be' more useful than its counterparts in certain applications. Hence, further modifications should be encouraged to widen the scope of its use and improve its biologic compatibility. References
1. Trerotola SO, Fair JH, Davidson D, Samphilipo MA Jr, Magee CA. Comparison of Gianturco Z stents and Wallstents in a hemodialysis access graft model. JVIR 1995; 6:387-396.
2. Dobben RL, Wright KC, Dolenz K, Wallace S. Gianturco C. Prostatic urethra dilatation with Gianturco self-expandable metallic stent: a feasibility study in cadaver specimens and dogs. AJR 1991; 156:757-761. 3. McGraw-Hill Encyclopedia of science and technology. Vol 16. 6th ed. New York, NY: McGraw-Hill, 1987; 598-599. 4. Roy S, Baijal SS, Phadke RV, Kumar S. Hybrid Gianturco expandable stent. AJR 1994; 162:449-450. 5. Gujral RB, Roy S, Baijal SS, Phadke RV, Ahlawat R. Srinadh ES, Rastogi H. Treatment of recurrent posterior and bulbar urethral strictures with expandable metallic stents. JVIR 1995; 6:427-432. 6. Baijal SS, Roy S. Phadke RV, Kumar S. Idiopathic BuddChiari syndrome: treatment with expandable Z stents (abstr). JVIR 1995; 6:58-59.
Dr Trerotola responds: We appreciate Dr Roy's interest in our work. We were indeed incorrect in stating that the ROsch-modified Gianturco Z stent does not contain solder. This stent does in fact contain solder, although the spiral modification does not. We regret the error and appreciate Dr Roy's comments. In the context of our manuscript (1) we wished to point out that an unsoldered stent such as the spiral Z stent might be less likely to encounter the type of fractures we saw. Like Dr Roy, we agree such an improvement would have to be solder free otherwise it might be at the expense of the type of inflammation we saw in our specimens. Reference
1. Trerotola SO, Fair JH, Davidson D, Samphilipo MA Jr, Magee CA. Comparison of Gianturco Z stents and Wallstents in a hemodialysis access graft model. JVIR 1995; 6:387-396.
Scott O. Trerotola, MD Department of Vascular and Interventional Radiology University Hospital, Room 0279 550 N. University Blvd Indianapolis, IN 46202-5253
Difficult Portal Vein Access in Transjugular Intrahepatic Portosystemic Shunt Placement From: Scott R. Kerns, MD Radiology Associates of Ocala 1490 SE Magnolia Ave Ext Ocala, FL 34471 I enjoyed reading the technique described by Sproat et al (~) for performing transjugular intrahepatic portosystemIC shunt (TIPS) placement successfully in patients in
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Gianturco Z Stents for Hemodialysis Grafts From: Sumit Roy, MBBS, MD Institute for Surgical Research, Rikshospitalet Pilestredet 32 N-0027 Oslo, Norway. Editor: A small error seems to have crept into the excellent paper by Trerotola et al on the comparative evaluation of stents in hemodialysis grafts (1). The authors suggest that the Gianturco-Rosch stent may be preferable to the Gianturco Z stent for hemodialysis grafts. As the subunits in the former are held together by suture, it is postulated that the problem of fractures of soldered joints causing stent migration will be eliminated. Selection of the Gianturco-Rosch device may in fact simply substitute one drawback with another. The severe inflammatory response noticed by the authors near the soldered joints would probably be exaggerated with the Gianturco-Rosch model. Unlike the Gianturco Z stent, the Rosch-modified version is soldered proximal to every bend in the wire to create an "eyelet," and thus is likely to produce five to six times as many foci of intimal inflammation as the former. The observations of Trerotola et al bring into question the advisability of using solder in the fabrication of this family ofstents. Not only is an alloy of uncertain biocompatibility used (1,2), but soldering is an inappropriate method for bonding stainless steel (3). A completely solder-free Z stent is not just a theoretical possibility (4) and has been successfully used in the urethra (5), the venous. system (6), and the biliary tract (Baijal et aI, unpubhshed data, 1994). The amount of solder on the Gianturco-Rosch stents can also be substantially reduced by eliminating the soldering of adjacent limbs near the be?-ds to cre~te the "eyelets." Though visually pleasing, thIS feature IS superfluous, contributing nothing to the configurational stability of the stent. From benchtop (Roy et aI, unpublished data, 1992) and clinical experience (6) it is evident that the configuration of the wire at this sit~ itself ensures that the suture loop does not migrate and the entire ensemble does not telescope during backloading into the delivery sheath. The results presented by the authors suggest that despite its simple design, the Gianturco Z stent may be' more useful than its counterparts in certain applications. Hence, further modifications should be encouraged to widen the scope of its use and improve its biologic compatibility. References
1. Trerotola SO, Fair JH, Davidson D, Samphilipo MA Jr, Magee CA. Comparison of Gianturco Z stents and Wallstents in a hemodialysis access graft model. JVIR 1995; 6:387-396.
2. Dobben RL, Wright KC, Dolenz K, Wallace S. Gianturco C. Prostatic urethra dilatation with Gianturco self-expandable metallic stent: a feasibility study in cadaver specimens and dogs. AJR 1991; 156:757-761. 3. McGraw-Hill Encyclopedia of science and technology. Vol 16. 6th ed. New York, NY: McGraw-Hill, 1987; 598-599. 4. Roy S, Baijal SS, Phadke RV, Kumar S. Hybrid Gianturco expandable stent. AJR 1994; 162:449-450. 5. Gujral RB, Roy S, Baijal SS, Phadke RV, Ahlawat R. Srinadh ES, Rastogi H. Treatment of recurrent posterior and bulbar urethral strictures with expandable metallic stents. JVIR 1995; 6:427-432. 6. Baijal SS, Roy S. Phadke RV, Kumar S. Idiopathic BuddChiari syndrome: treatment with expandable Z stents (abstr). JVIR 1995; 6:58-59.
Dr Trerotola responds: We appreciate Dr Roy's interest in our work. We were indeed incorrect in stating that the ROsch-modified Gianturco Z stent does not contain solder. This stent does in fact contain solder, although the spiral modification does not. We regret the error and appreciate Dr Roy's comments. In the context of our manuscript (1) we wished to point out that an unsoldered stent such as the spiral Z stent might be less likely to encounter the type of fractures we saw. Like Dr Roy, we agree such an improvement would have to be solder free otherwise it might be at the expense of the type of inflammation we saw in our specimens. Reference
1. Trerotola SO, Fair JH, Davidson D, Samphilipo MA Jr, Magee CA. Comparison of Gianturco Z stents and Wallstents in a hemodialysis access graft model. JVIR 1995; 6:387-396.
Scott O. Trerotola, MD Department of Vascular and Interventional Radiology University Hospital, Room 0279 550 N. University Blvd Indianapolis, IN 46202-5253
Difficult Portal Vein Access in Transjugular Intrahepatic Portosystemic Shunt Placement From: Scott R. Kerns, MD Radiology Associates of Ocala 1490 SE Magnolia Ave Ext Ocala, FL 34471 I enjoyed reading the technique described by Sproat et al (~) for performing transjugular intrahepatic portosystemIC shunt (TIPS) placement successfully in patients in
985