Focal Stenting:Does it Make Sense?John McB. Hodgson, MDAssociate Professor of MedicineCase Western Reserve UniversityCleveland, Ohio
In the accompanying manuscript about stent implantation usinga single balloon, Mudra et al.  report the first controlled series ofstent implants using the focal stenting concept. They used a newballoon with differential compliance characteristics wherein thecentral portion can expand to a greater degree than the end portions.This approach allows the operator to visually assess the degree ofballoon expansion by seeing the central portion expand underfluoroscopy. In theory, stent expansion is maximized while edgedissections are minimized.
This study was well done and provides interesting pilot data forthe focal stenting concept. The authors conclude that use of thisballoon allowed for a reduction in the number of balloons used percase. They used 58 balloons for 50 lesions (1.16/lesion). Thiscompares very well with three recent randomized trial results usingconventional strategies (2.3/lesion , 2.1/lesion , and 2.4/lesion ). As in these other trials, the key element appears to bethe ability to both predilate and high pressure post-dilate with asingle balloon. The ability to see the balloon expansion on fluorooffers a nice advantage over conventional balloons. We all areaware of compliance charts and the poor correlation between themeasured balloon size in vivo and the chart size. When thedifferential size balloon can be seen to be larger in the center, theoperator can be assured that the vessel resistance has beenovercome and that the central portion is greater than nominal insize.
The angiographic and intravascular ultrasound (IVUS) resultsobtained were excellent (even before additional balloon use). Weachieved similar clinical and quantitative results  using acombined IVUS-variable diameter balloon (Oracle Focusy) basedon the same device used by Mudra et al. . How much of thisresult was unique to the focal stenting concept, however, isunknown due to the lack of a concurrent control group. Theongoing OSTI-II trial may answer this question. In the OSTI-IItrial, CATy balloons were used following optimal angiographicstent implantation at 18 atmospheres with a conventional balloon.Preliminary results suggest that further improvement can beachieved after using the CATy balloon (Gregg Stone, personalcommunication).
A number of concerns are also raised by this study. Importantly,two stents were stripped from the balloon during attemptedinsertion. While no complications occurred, this 4% rate ofdislodgement is clearly unacceptable. The current device has a 10mm central section. Additional lengths will need to be tested if thisballoon concept is to be applicable to the wide range of stentedlesions. A 15 mm central section version with 2 markers has beendeveloped and facilitates implant for 15 mm long stent designs. Theinvestigators comment on the poor profile and flexibility of the firstgeneration CATy catheter. Newer versions using the same differen-tial sizing concept have been developed with much lower profiles(e.g., 3.0 mm balloon: 0.0289 vs. 0.0369), and in our experiencehave reduced the problems with predilation crossing and tracking.In eight cases, Mudra et al.  required a 0.5 mm larger balloon. Itis possible that greater compliance (or size differential) in the stentsegment is needed to accommodate these cases where evenexperienced operators have undersized the balloon, or when lesionsare resistant to dilation. The mechanism of action of this newballoon during stent expansion also remains unexplained. It ispossible that it works via longitudinal redistribution of plaque asseen by IVUS in the Multilinky experience . T his was notaddressed by the investigators.
As stent implantation continues to increase in frequency andcomplexity, safer and more efficient implantation strategies will bedesirable. Mudra et al.  have provided a nice look at how newballoon designs may be helpful.
REFERENCES1. Mudra H, Werner F, Regar E, Klauss V, Henneke K-H, Rothman M,
di Mario C: One balloon approach for optimized Palmaz-Schatzstent implantation: The MUSCAT trial. Cathet Cardiovasc Diagn42:130136, 1997.
2. Ricci DR, Penn IM, Moscovich MD, Buller CE, Lepicq L, KrukoffM, Cusma J, Green C, Zubaid M, Chauhan A: Reduction of stentcosts with high pressure stent delivery systems: Results of arandomized study. (Abstract) J Invas Cardiol 8:55, 1996.
3. Rocha-Singh K, Lucore C, Trask R, Womack K: An effectiveprocedural cost containment strategy for coronary stent deployment.(Abstract) J Invas Cardiol 8:55, 1996.
4. Waksman R, Shafer CD, Seung KB, Shen Y, Weintraub WS, KingSB III: Intracoronary stent implantation using a single high-pressureperfusion catheter. Cathet Cardiovasc Diagn 40:140143, 1997.
5. Muller C, Frey AW, Roskamm H, Hodgson JMcB: Single deviceapproach to ultrasound-guided percutaneous transluminal coronaryangioplasty and stenting: Initial experience with a combinedintracoronary ultrasound/variable diameter balloon. Cathet Cardio-vasc Diagn 40:393399, 1997.
6. Honda Y, Yock CA, Hermiller JB, Fitzgerald PJ, Yock PG, for theMULTI-LINKy investigators: Longitudinal redistribution of plaqueis an important mechanism for lumen expansion in stenting.(Abstract) J Am Coll Cardiol 29:281A, 1997.
The author(s) indicated has (have) completed a Disclosure Statementas required in the Instructions to Authors. It is on file in the office of theEditor-In-Chief.
Catheterization and Cardiovascular Diagnosis 42:137 (1997)
r 1997 Wiley-Liss, Inc.