Status of Stents
Eduardo Escorcia, MD, and Jay Hollman, MD he useof intraarterial stentswas first describedby Dotter’ in 1969. Coronary stenting was introduced by S&wart et al2 using the Medivent Wallstent. Initial and long-term results of this stent have been described.3p4Other stents tested in human coronaries include the Palmaz-Schatz5and GianturcoRoubin6 stents. In this issue of The American Journal of Cardiology, de Jaegereet al7 describe the initial European experience with the Wiktor stent. Phase I U.S. clinical trials of this device were recently completed at the Ochsner Clinic in New Orleans. Table I summarizes design, material, complications and percentage of successof the different stents most frequently ~sed.~-iOIt is not easy to decide which device should be considered best. Whereas the Wiktor stent (with better visibility) presentsa high technical success and easeof implantation, the Palmaz-Schatz is currently the most widely used in the U.S. Although intensive anticoagulation is necessary,the subacuteocclusion rate appearsto be less for this device. The ideal stent should be visible, but have the minimal amount of material. The stent with the greatest amount of metal (the Wallstent) appears to have the highest rate of thrombosis. Reducing the amount of stent material also appears to decreaserecurrence rates.’ l Complications of stenting: Acute or subacute thrombosis is a major complication of stenting.7 It is most likely responsiblefor sudden death that can occur during the first days after implantation or even several months later. Several factors play an important role in the development of thrombosis: material of the stent, percentage of the area covered by the device, lack of coating with anticoagulants, lack of aggressivesystemic anticoagulation, and perhaps hemodynamics that may affect the blood flow. The stents differ in inherent thrombogenicity becauseof surface chemistry, amount of stent material present, and electrical charge of the metal used. Significant hemorrhagic complications (secondaryto anticoagulant therapy) have been reported in all studies of stent implantation. This can vary from groin site hematomas to gastrointestinal and genitourinary hemorrhages needing blood transfusion, and unfortunately, death due to cerebral hemorrhage.5 Stenting probably doesnot reduce neointimal hyperplasia. This is logical, becausestent placement doesnot modify the basic healing process after arterial injury.12,13Ellis et all4 are correct in postulating that any effect on recurrent stenosisis related to the initial effect
From the Department of Cardiology, Ochsner Clinic of Baton Rouge, Baton Rouge, Louisiana. Manuscript received September 26, 1991; revised manuscript received November 8, 199 1, and accepted Novemher 9. Address for reprints: Fzduardo Escorcia, MD, Department of Cardiology, Ckhsner Clinic of Baton Rouge, 16777 Medical Center Drive, Baton Rouge, Louisiana 708 16.
on initial geometry. After injury to the vesselwall, several factors interact to change smooth cell phenotype to produce synthesis rather than contractility.i5,16 This proliferation of smooth and fibrous cells coversnot only the entire stent area, but also (when excessive) (decreasesthe luminal diameter of the vessel. Cost is also a factor to be considered.Cost for stent implantation is about 2.5 times that of routine percutaneous transluminal coronary angioplasty (PTCA).17 The main reason for this is the prolonged hospitalization needed to stabilize anticoagulation therapy. This disadvantage must be outweighed by a significant advantage to stenting to make this technique cost-effective. The costs of the stent and delivery catheter (when different from the dilating catheter) are sure to add to total cost. Benefits of stenting: The benefit of the stent implantation for correcting the deformed luminal geometry of an injured vessel wall has been well-demonstrated by quantitative angiographic studies.3,18 Implantation after balloon angioplasty produces an additional increase in minimal luminal cross-sectionalarea and obstruction diameter. It also decreasedthe percent area and diameter of stenosis.lg Becausethe functional significance of a stenotic lesion is directly related to the expectednormal cross-sectionalarea of the vesselat the point of obstruction, the stent produceshemodynamic improvement: decrease of pressure gradient across the stenosis and of turbulent resistance.20 Theoretical advantages,such as reduction of elastic recoil beyond the initial improvement in geometry, decreased spasm in the area of stent placement and decreasedthrombosis due to less exposure of the injured arterial surface,,remain unproved. In fact, elastic recoil occurs immediately on deflation of the balloon or not at all. Vasospasm8occursalmost universally after PTCA.21 Theoretically, stenting should reduce this, but in actual fact stenting may induce spasmof the distal artery. The risk of thrombosis appears to be greater and not less with stenting. Indications for stenting: The usefulnessof stenting in bad or suboptimal geometry, or with a large intimal tear or flap, or both, has been demonstratedin selected patients.22-23It has saved patients the risk and cost of emergencycoronary artery bypassgraft surgery. In this case,it is important to assessthe vesselbefore deciding on the feasibility of the stenting procedure. (Large or medium size vesselswith lesions in the straight part of the proximal vesselwith good distal runoff are good for bail-out stenting. Distal lesionsor those in small arteri,es [13.0 mm] should not be stented.) Stenting is not the only method to improve suboptima1 results after routine PTCA. Directional atherectomy has beenusedby us and other investigators,24with good improvement of suboptimal results. The disadvantagesof atherectomy are risk of arterial perforation,25,26 EDITORIALS
of Stents in Current
Balloon-expanding Gianturco-Rubin6~10~2g Palmaz-Schatz (articulated)5f8fg Wiktor7 Self-expanding Wallstent
Stainless steel Stainless steel Tantalium Stainless steel
Acute & Subacute Thrombosis
Poor Poor Better Poor
95-97% 95% 98% 98%
6% 0.6-2X% 10% 24%
the relatively large size of the device, and inability to advance the device beyond the proximal portion of the arteries. Other atherectomy devices also hold promise for improving suboptimal results after routine PTCA. Arterial dissection has also been treated with a laser balloon catheter developedby Spears.This method improved arterial dissection, obviating bypasssurgery in a high percentageof patients. Laser thermal balloon angioplasty has a relatively high recurrent stenosisrate and uses an expensive,nonportable form of thermal energy. Availability of these newer deviceswill hopefully lessen the risk of emergency bypass surgery after suboptimal routine PTCA. Becauseacute occlusion and large dissectionsoccur in only about 5% of routine PTCA cases, the market for this indication is relatively small. When to use stenting or the other devicesremains to be determined. Recurrent stenosis: Stenting for treatment of coronary restenosishas not shown an overall significant decrease of recurrence compared with that of PTCA. Teirstein27 cited the 6% recurrence rate in de novo, short obstructions after stenting with the Palmaz stent as evidencethat recurrent stenosisis lessenedby the use of stents.There were oaly 50 patients stentedwith these ideal lesion characteristics. Patients receiving multiple stents or stents for recurrent stenosislesionshave recurrence rates of 47 and 35%, respectively. Thus patients with long lesions, recurrent stenosislesions and lesions in smaller arteries are less likely to benefit from coronary stenting. Patients who need help the most are benefited the least. On a statistical basis, patients at high risk of recurrence should be most likely to demonstrate benefit, if a real benefit is present.Advocatesof stenting want us to believe the opposite is true. As more and more careful studies are performed it is clear that recurrent stenosisafter routine PTCA is closely lmked to lesion morphology and residual stenosis.28There is a relation betweenthe incidence of restenosisand the severity and length of the initial lesion, and also the greater degree of residual stenosisafter angioplasty. Long, severe lesions and those with high residual stenosisare more likely to recur. Low recurrence rates in ideal lesionsafter stenting may be due more to the lesion than the stent. Small vessels (where stents are contraindicated becauseof increasedrates of thrombosis) are more likely to recur. Until randomized trial data are available on recurrence, stenting to prevent recurrent stenosisis an unproven hypothesis. In our opinion, use of the stent to prevent coronary restenosis(apart from a randomized trial to investigate this) is not justified. Stenting in its current forms has a significant increased risk of subacute occlusion and 666
THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 69
Myocardial Infarction 2.6% 2.8%
Late Restenosis 35-40% 35%
Hemorrhagic Complications 16% 5.7-15% >22%
hemorrhagefrom anticoagulation, and an increasedcost for the device and protracted hospitalization. The stent is an experimental device now acceptedas a “bail out” procedure when an acute occlusion or dissection occurs after routine PTCA. REFERENCES
1. Dotter CT. Transluminally-placed coilspring endoarterial tube graft. Longterm patency in canine popliteal artery. Znues?Radio1 1969;4:327-332. 2. S&art V, Puel J, Miskovith V, Joffre I, Kappenberger L. Intravascular stentsto prevent occlusionand restenosisafter PTCA. N Engl J Med 198X316: 701-706. 3. SerruysP, StraussBH, Beatt KJ, Bertrand NE, Puel J, Rickards AF, M&r B,
Goy JJ, Voyt P, KappenbergerL, @wart V. Angiographic follow-up after placement of a self-expandingcoronary artery stent. N EngZJ Med 1990;324:13-17. 4. Urban P, Sigwart V, Golf S, Kaupmann V, Sadeghi H, Kappenberger L. Intravascular stenting for stenosisof aortomronary venousbypassgrafts. J Am Co11Cardiol 1988;13:1089-1091. 5. Schatz RA, Bain DS, Leon M, Ellis SG, Goldberg S, Hiishfeld JW, Cleman HW, Cabin HS, Walker C, Stagg J, Buckbiider M, Teirstein PS, Top01EJ, SavageM, Perez JA, Curry RC, Whitworth H, Soresa E, Tio F, Almagor Y, Ponder R, Penn IM, Leonard B, Lesine S, Fish D, Pahnaz JC. Clinical experienceswith the Palmaz-Schatzcoronary stent:initial resultsof a multicenter study. CircuZa?ion 1991;83:148-161. 6. Roubin GS, King SB III, DouglasJS, LemboNJ, Robin KA. Intrawronary stenting during percutaneoustransluminal coronary angioplasty. Circulation 1990;81:IV-92, IV-100. 7. de JaegereP, Serruys P, Bertrand M, Wiegand V, Kober G, Marquis JF, Valeix B, Uebis R, PiessensSJ.Wiktor stentimplantation in patientswith restenosis following balloon angioplasty of a native coronary artery. Am J Cardiol 1992;69:598-602. 8. Schatz RA, Leon M, Bain DS, Ellis S, Marco J, Erbel R, Golberg S. Shortterm clinical results and complications with the Palmaz-Schati coronary stent (abstr). J Am Co11 Cardiol 1990;15:117A. 9. Ellis SG, SavageM, Bairn D, Hirshfeld J, Cleman M, Teirstein P, Top01EJ. Intracoronary stenting to prevent restenosis:preliminary results of a multicenter study usingthe Palmaz-Schatzstent suggestbenefit in selectedhigh risk patients (abstr). J Am Coil Cardiol 1990;15:118A. 10. Roubin GS, Hearn JA, Carlin SF, Lembo NJ, Douglas JS, King SB III. Angiographic and clinical follow-up in patients receiving a balloon expandable, stainless-steel,stent (Cook, Inc.) for preventionor treatment of acuteclosureafter PTCA. Circulation 1990;82:11-191. il. Tominaga R, Harasaki H, Emote H, Kambik H, Hollman J, Sutton C. Effects of stent designand serumcholesterollevel on the restenosisrate (abstr). Circulation 1990,82:11-656. 12. Liu MW, Roubin GS, King SB III. Restenosisafter coronary angioplasty: potential biologic determinants and role of intimal hyperplasia. Circulation i989;79:1374-1387. 13. Sutton CS, Tominaga R, Harasaki H, Emote H, Oku T, Kambic HE, Skibiiki C, Beck G, Hollman J. Vascular stentingin normal and atherosclerotic rabbits. Studies of the intravascular endoprosthesisof Titanium-Nickel-alloy. Circulation 1990;81:667-683. 14. Ellis SG, SavageM, Bairn D, Hirshfeld J, Cleman M, FeinsteinP, Top01EJ. Intracoronary stenting to prevent restenosiszpreliminary resultsof a multicenter study using the Palmaz-Schatzstent suggestbenefit in selectedhigh risk patients (abstr). J Am CONCardiol 1990;153118A. 15. Clowes AW, Schwartz SM. Significanceof quiescentsmoothmusclemigration in the injured root carotid artery. Circ Res 1985;56:139-145. 16. C1owe.s AW, Glower NM, Reidy MA. Kinetics of cellular proliferation after arterial injury: endothelial and smooth muscle growth in chemically denuded vessels. Lab Invest 1986;54:295-303. 17. Dick RJ, Bureek KA, Muller W, Top01ET.The incrementalcostsassociated with theuse of new percutaneouscoronary devices.Circulation 1990;82:111-171. 18. Reiber JHC, SerruysPW, Kooijman CJ, Wijns W, SlagerCJ, GerbrandsJJ, SchuurbiersJCH, Boer AD, Hugenholtz PG. Assessmentof short, medium and long-term variation in arterial dimensionsfrom computerassistedquantitation of coronary cineangiograms.Circulation 1985;71:280-288.
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19. Serruys PW, Guilliere Y, Bertrand M. Additional improvementof stenosis geometry in human coronary arteries by stenting after balloon dilatation. Afi J Cardiol 1988;61:7-16. 20. S&wart V, Kaufmann J, Goy JJ, KappenbergerL. Suppressionof residual transtenotic pressure gradient after PTCA by implantation of self-expanding stents. Circulation 1987;76:IV-186. 21. Fishell TA, Derby G, Tse TM, Stadius ML. Coronary artery vasoconstriction routinely occurs after PTCA: a quantitative arteriographic analysis. Circulation 1988;78:1323-1334. 22. Sigwart V, Urban P, Golf S, Kaufmann U, Imbert C, Fischer A, Kappenberger L. Emergencystentingfor acuteocclusionafter balloon angioplasty.Circulation 1988;78:1121-1127. 23. Roubin GS, King SB III, DouglasJS. Intracoronary stentingdaring percutaneous transluminal coronary angioplasty. Circulation 1990;81:IV-92-IV-100. 24. Vetter JW, SimpsonYB, RobertsonGC, SelmonMR, Rowe MH, Bartzokis TC, Braden LJ, Hinohara T. Review directional coronary atherectomy for failed
balloon angioplasty (abstr). J Am CONCardiol 1991;17:384A. 25. Muller DWM, Ellis SG, Dehowe DL, Topol GJ. Quantitative angiographic compensationof the immediatesuccessof coronary angioplasty,coronary atherectomy and endoluminal stenting. Am J Cardiol 1990;66:938-942. 26. Rowe MH, Hinohara T, White NW, RobertsonGC, Selmon MR, Simpson JB. Comparisonof dissectionnotesand angiographicresultsfollowing directional coronary atherectomy and coronary angioplasty. Am J Cardiol 1990;66:49-53. 27. Teirstein PS. Stent and restenosis:do coronary stentspresent restenosis?J Itwas Cardiol 1991;3:67B-71B. 28. Hirshfeld JW, Schwartz JS, Jugo R, MacDonald RG, Goldberg S, Savage MP, BassTA, Vetrovec G, Cowley M, TaussigAS, Whitworth HB, Margolis JR, Hill JA, PepineCJ, Hill JA. Restenosisafter coronary angioplasty:a multivariety statistical model to relate lesion and procedure variables with restenosis.J .4m Coil Cardiol 1991;18:647-656. 29. Macander PJ, Agrawa SK, Roubm GS. The Gianturco-Roubin balloonexpandableintracoronary flexible coil stent. J has Cardiol 1991;3:85-94.
Inappropriate Terminology in Publications Concerning Aortic Balloon Valvuloplasty Francis Robicsek, MD risks (see “contraindicated”). Frequently, the reader turns a few pages,examinesthe tables and charts carefully, and finds to his/her consternation that “non-surgical” simply implies that the patients (for various reasons) have not undergone surgery! These reasonsmay include not only true contraindications, but also higher than usual (but certainly not prohibitive) operative risks and patients who are not high surgical risks at all, but do not undergo surgery for other reasonssuch as mental debilitation and refusal for religious or personalreasons. In some cases,such as the Harvard experience of 1’70 patients with aortic balloon valvuloplasty,’ the share of patients included in the “non-surgical” group for the sole reason of refusal was >32%! To label such a group “non-surgical” is misleading. In the protocol of the recent Mansfield Scientific Balloon Valvuloplasty Registry (Mansfield Scientific Incorporated, Mansfield, Massachusetts), the term “non-surgical” was defined as: “Patients with high risk for valve replacementor patients who have refused surgery.” Reading this, one may expect that the processIof determining who is “high risk” for valve replacement and should therefore not undergo surgery is a complex one in which the surgeon did indeed participate. However, in the Mansfield study, only “thirty-one percent of the total group had been formally denied surgical valve replacementas documentedin writing by the consulting cardiovascular surgeon.“2 In other words, in the lion’s share of cases,declaring the patient unfit for surgery was done without surgical consultation. Also, regarding patients who would have been candidates for surgery but refused, one would expect that a surgeon had been given the chance to discussthe matter with the patient, but again, this did not materialize in most cases. The controversial expression“high risk” for surgery, From the Heineman Medical ResearchLaboratory and the Carolinas per se, is not very informative. In the complex setting of Heart Institute at the Carolinas Medical Center, Charlotte, North clinical medicine one needs to know not only that the Carolina. Manuscript received July 16, 1991; revised manuscript rerisk of a procedure is “high,” but also how ‘this risk ceived and acceptedNovember 7,199l. Address for reprints: Francis Robicsek, MD, Heineman Medical compareswith the natural course of the disease,as well ResearchCenter, P.O. Box 35457,Charlotte, North Carolina 28235. as the alternative treatment modalities. Currently, in an
t has been customary to refer to patients in need of surgical treatment, but in whom the extent of disease or associatedconditions, or both, would have made operative intervention futile or risky beyond expected benefits as “inoperable.” Inoperable (literally translated as “non-operable”) is an inappropriate term. Anybody can be operated on, even those who should not be. Although it is still usedin everyday medical jargon, in professional writing it has been largely replaced by more proper terms such as “contraindicated” (i.e., although technically feasible, by someprofessionalcriteria it should not be performed) or “relatively contraindicated,” which implies the presence of factors constituting either an unreasonablehazard to health or life, or a situation that would make intervention unlikely to succeed.The term “absolute contraindication” is usually applied to a scenario in which these factors reach prohibitive severity. “Non-indicated” simply implies that the patient may be managed more effciently by other than surgical means. In recent times, a new term becamecommonplacein professionalwriting: “non-surgical.” This word has been used repeatedly to describecohorts of patients who have undergone balloon valvuloplasty for calcified aortic stenosis. Surgeons seldom use the word “non-surgical,” and it seemsthat only “non-surgeons” appreciate what is “non-surgical” and use the term in such a way that its meaning seemsto change from study to study, even if the term comes from the pen of the same author. An average reader of medical publications is likely to interpret the term “non-surgical” (sometimesalso referred to as “non-operative”) as a category of patients who after careful evaluation were found to be unsuitable for surgical intervention owing to prohibitively high