Intracoronary Stent Dislodgment: Updated StrategyEnabled by the New Generation of Materials

Mark Patterson,* MRCP, and Ton Slagboom, MD

Stent dislodgment remains a vexing problem in percutaneous coronary intervention.The technological improvements in machine-crimped premounted stents have led to areduced incidence of dislodgment but may have exacerbated the problem of stent dis-lodgment (SD). Previous reports describing the management of SD have concentratedpredominantly on manually mounted stents. We present a case where the position of adislodged premounted stent in the distal left main stem was unfavorable for previouslydescribed solutions. The problem was elegantly resolved by taking advantage of theimproved performance of the current generation of wires and balloons to achieve arapid first-rate clinical outcome. ' 2006 Wiley-Liss, Inc.

Key words: coronary; angioplasty; transluminal balloon; stent

INTRODUCTION

Registries show that the use of premounted stentshas reduced the chance of stent dislodgment (SD) [1].However, the growth of percutaneous coronary inter-vention (PCI) procedures results in SD remaining asignificant problem in PCI despite having a proportion-ately reduced rate of incidence. Stent dislodgment andembolization can have serious consequences, includingmyocardial infarction [2,3], cerebro-vascular accident(CVA) and death [1], while emergency surgery forstent removal risks a high mortality rate [1].Machine-crimped premounted stents are more diffi-

cult to dislodge due to a number of improvements dur-ing manufacture that have led to an increased stentretention force. This improvement of attachment meansthat greater force is required to dislodge the machine-crimped stent compared to a manually crimped stent.The stent, therefore, may jam more tightly or in a moretortuous position in the coronary artery, thus increasingthe risk of retrieval.We describe a case of SD in the distal left main

stem (LMS) across an abnormal left anterior descend-ing artery (LAD) ostium. This location was unfavor-able for the use of retrieval techniques or for in situ di-lation that might damage the LMS and/or compromisethe LAD. Appreciation of the improvements in the per-formance, profile, and flexibility characteristics of thelatest generation of wires and balloons compared toprevious generations permitted a rapid and elegantresolution to the problem.

CASE REPORT

A 74-year-old man with stable angina was admittedelectively for two-vessel PCI to a proximal Cx lesion

and a mid-LAD lesion. The LMS was calcified andtapered distally. The distal LMS and proximal Cx wereseen to have a tortuous anatomy (Fig. 1). The ostiumof the LAD was noted to be moderately narrowed.Informed consent was obtained. The right radial ar-

tery was cannulated using the Radifocus introducer IIsystem (Terumo). The routine medications for theradial approach in our institution consisting of an intra-arterial antispasm cocktail of 200 lg of nitroglycerineand 5 mg of verapamil followed by 10,000 units ofheparin were given. A 6 Fr multipurpose catheter wasused as guide support. A Galeo wire (Biotronik) waspassed to the distal Cx and an attempt was made toplace a 3.5 3 20 mm Lekton Motion (Biotronik) directlyin the vessel but failed to cross the lesion. Duringattempted stent withdrawal, resistance was felt. Angi-ography showed that the stent had partially dislodgedfrom its normal position on the balloon, with clearseparation of the balloon markers from the radio-opaqueends of the stent (Fig. 2). The stent was partially locatedin the distal LMS and partially in the Cx, therefore

Amsterdam Department of Interventional Cardiology, OnzeLieve Vrouwe Gasthuis, Amsterdam, The Netherlands

*Correspondence to: Dr. Mark Patterson, t.a.v. Secretariaat Cardiolo-

gie P2, Amsterdam Department of Interventional Cardiology, OLVG,

Postbus 95500, 1090 HM, Amsterdam, The Netherlands.

E-mail: markspatterson@doctors.net.uk

Received 27 July 2005; Revision accepted 9 December 2005

DOI 10.1002/ccd.20632

Published online 10 February 2006 in Wiley InterScience (www.

interscience.wiley.com).

' 2006 Wiley-Liss, Inc.

Catheterization and Cardiovascular Interventions 67:386–390 (2006)

across the abnormal ostium of the LAD and partiallybent to curvature of the coronary vessels (Fig. 2).A Choice LS wire was passed parallel to the dis-

lodged stent and a 2.5 3 20 mm Maverick (BostonScientific) was used to predilate distally to the stent(Fig. 3, left).After balloon retrieval, the stent could now be

advanced completely and was successfully deployedacross the Cx lesion (Fig. 3, right). The distal end ofthe stent was not fully deployed (Fig. 4), so the entirelength of the stent was postdilated with a 4.0 3 20 mmMaverick balloon (Fig. 5) to ensure full strut appositionand this achieved a good angiographic result (Fig. 6).The PCI to the LAD was uncomplicated and the

procedure was concluded with the patient remainingasymptomatic throughout. Reopro was given and hewas discharged after an uneventful overnight stay withan unchanged ECG and normal cardiac enzymes.

DISCUSSION

Stent dislodgment remains a vexing complication ofPCI. Registries show a reduction in the rate of dislodg-ment from 1.04% with manually crimped stents to0.27% with the advent of premounted stents [1].Stent technology has undergone a number of im-

provements. Particularly relevant to SD is the develop-ment of improved stent retention force (SRF), i.e., the

force required to pull the stent from an undeployedballoon. The specific values of stent retention force fordifferent makes of stent are not routinely released bythe respective companies but current registries showno significant difference in rates of SD between dif-ferent stents. SRF is increased using a variety of strat-egies during manufacture. An increase in the degree ofballoon folding enhances the uniformity/regularity ofboth the advancing profile and of strut deploymentwith expansion. Commonly only two folds are possibleduring manual crimping (two fingers), producing anunequal distribution of struts over the balloon and anirregular advancing profile. Additionally, manual crim-ping may not flatten all the stent struts uniformly andany exposed struts may encourage snagging and dis-lodgment [4]. Stent crimping performed by machineoccurs in a circumferential manner around the balloon,improving the advancing profile and reducing varia-tions in pressure on the struts during balloon inflation,which enhances uniform strut distribution. A secondstrategy for improving SRF is pressurizing the balloonwhile fixing the stent within the crimping apparatus.This process pushes ‘‘pillows’’ of balloon materialbetween the stent struts, partially embedding the stenton the balloon and ramping balloon material at the dis-tal and proximal edges of the stent. In addition to theimprovements related to SRF, stents are also designedwith better flexibility secondary to changes in strutdesign and in possible articulation points. Improve-ments in ancillary equipment include new designs ofguidewires, reduced balloon profiles, and increased guid-ing catheter inner diameter. Such factors have im-proved performance and allow stent delivery toincreasingly difficult locations with lower relative ratesof stent loss. However, these improvements encourageprocedures where stents become more deformed andsuffer greater shear forces than previously. This mayresult in the stent becoming dislodged in a more distallocation, in a more tortuous location, or a tighterlesion, thereby complicating management. On the otherhand, increases in SRF may accentuate the tactile feel-ing when the stent begins to dislocate, therefore allow-ing earlier recognition, i.e., before complete separation,as seen in this case.Published literature describing solutions for SD mostly

predates the widespread use of premounted stents andincludes dislodgment occurring outside the coronary tree.Retrieval techniques have been extensively described,including stent capture using a partially inflated balloon[1,5], balloon placement distal to the stent [6], twistedguidewires [7], snares, e.g., gooseneck snares [1,8], amultipurpose basket [8], and a variety of forceps, e.g.,myocardial biopsy forceps [1], 3.0 Fr forceps [9], 5 FrAlligator forceps [10], and 6 Fr bioptome forceps [11].

Fig. 1. Proximal LCA with tapering calcified LMS, abnormalLAD ostium, and proximal Cx lesion (arrowed).

Novel Strategy for Stent Dislodgment 387

Such techniques have the dual disadvantages of aninnate risk of stent loss during withdrawal coupled withthe possibility of damage to passing structures as thestent and retrieval apparatus are removed. Furthermore,some techniques, e.g., cutting forceps, may risk wire,

balloon, or stent damage or potentially, severing of thewire. Deployment at an unintended site has also beensuggested in both the coronary arteries [12] and in peri-pheral arteries [13,14]. However, placement at an unin-tended location remains undesirable. Stent advancement

Fig. 3. Left: Predilation of Cx with a second wire and a new Maverick balloon. Right: Deploy-ment of successfully advanced stent.

Fig. 2. Left: Contrast injection to show position of separated stent-balloon in the distalLMS-proximal Cx upon attempted withdrawal. Right: Marker separation from stent visualizedwithout contrast injection (arrowed).

388 Patterson and Slagboom

on a partially inflated low-profile new balloon has beenused on occasion [1], but only described in dislodgedmanually crimped stents captured on a new balloon.Retrieval in this case was a possibility, e.g., with

snares or twisted wires. However, manipulation of fur-ther devices in the LMS risked damage either with

device manipulation or with retraction of the possiblydamaged and deformed stent back through the LMS.Capture of the stent on a balloon has been described

in manually crimped stents. In this case, the stent wasstuck across the LAD ostium as well as in a curve. Asoft expansion of a balloon would tend to straighten

Fig. 4. Left: Postdeployment image showing lesion improvement. Right: Distal end of stentincompletely deployed (arrowed).

Fig. 5. Postdilation with 4.0 mm balloon to ensure completestrut apposition. Fig. 6. Final result with stent deployed at intended site in

proximal Cx.

Novel Strategy for Stent Dislodgment 389

the stent and might jam the stent further, thus riskingdeployment.Deployment of the stent has occasionally been sug-

gested. In this case, this was felt to be undesirable.First, deployment of the stent in the LMS might com-promise the abnormal LAD ostium. Second, the LADrequired PCI that might be more difficult when tryingto advance a second stent through the proximal stent.Third, deployment of the stent in the LMS would riskthe dangers inherent with unprotected LMS PCI aswell as later in stent restenosis.In the case described, we inserted a new guidewire

and predilated the lesion with an angioplasty balloon.This allowed the procedure to be completed by ad-vancement of the stent. If stent advancement had notbeen possible, then other strategies would still havebeen an option as above. Furthermore, should the twistedwire technique be considered, the second wire wouldnow be in place.Our solution in this case of SD risked minimal dam-

age to the LMS, avoided the risky withdrawal throughthe vasculature, needed no infrequently used devices,and was performed with a 6 Fr catheter via our stand-ard radial approach. This technique does not precludeother solutions for stent dislodgment if unsuccessfuland therefore is worth consideration in similar cases.

ACKNOWLEDGMENTS

The authors are grateful to Joep Maeijer for help inpreparation of the images.

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