Major Longitudinal Deformation of a New-Generation Drug-Eluting Stent During Withdrawal Into the Guide Catheter

ABSTRACT: Longitudinal stent deformation is a recently described complication of percutaneous coronary intervention and is the result of modifications to the stent design that have reduced the number of connectors, reducing longitudinal stent strength. All previous reported cases involved deformation of successfully deployed stents. We report an unusual case of significant longitudinal deformation of a non-deployed Taxus Element stent during withdrawal into the guide catheter. To the best of our knowledge, this is the first such case ever reported.

J INVASIVE CARDIOL 2012;24(12):E318-E320

Key words: longitudinal stent deformation, PCI complications, stent compression, stent platforms 

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The longitudinal strength of some of the newer-generation stents currently used in the market has been brought to medical attention by several recent reports describing the occurrence of longitudinal stent deformation (LSD) after successful stent deployment with adverse events as serious as stent thrombosis or emergent coronary artery bypass graft.^1-4 Several causal mechanims were identified, such as guide catheter compression of stents deployed in an ostial location and non-ostial stents compression by either postdilatation balloon, guide catheter extension, proximal embolic protection device, or intravascular ultrasound (IVUS) catheter. LSD was mainly identified on angiography because of a focal increase in stent radio-opacity at the site of deformation. Once the deformation has occurred, rewiring and subsequent postdilatations appeared to be extremely difficult in several cases. Although this complication has been observed in various stent designs, the majority of the cases did involve the Element platform and a few with the Driver Platform, suggesting reduced longitudinal strength in these specific platform designs. This hypothesis has been reinforced by a recent independent study with standardized bench-top testing, demonstrating that stents with only two connectors between hoops, such as the Element stent or the Driver stent, required significantly less force to be compressed up to 5 mm and elongated by 1 mm than designs with more connectors.⁵ Of note, all previous cases  involved the deformation of deployed stents. Therefore, Williams et al have defined LSD as the distortion or shortening of a stent in the longitudinal axis following successful stent deployment.² Here, we report an unusual case of significant longitudinal deformation of a Taxus Element stent before stent deployment. To the best of our knowledge, this is the first case ever reported.

Case Report. A 59-year-old man was admitted for elective percutaneous coronary intervention (PCI) of a long and calcified stenosis involving the proximal and mid portion of the left anterior descending artery (LAD; Figure 1A). An ATW wire (Cordis Corporation) and a Whisper wire (Abbott Vascular) were placed in the distal LAD and the second diagonal branch, respectively, for side-branch protection as part of a provisional stenting approach. After predilatation with a 3 and 3.5 mm scoring compliant balloon (OrbusNeich), it was planned to cover the full lesion with a 3.5 x 38 mm Taxus Element stent (Boston Scientific). A first attempt to pass the lesion with the stent failed. On withdrawal of the crimped stent, the guide catheter was pulled in and engaged the distal left main (LM). Concomitantly, the proximal edge of the stent was blocked at the distal tip of the guide catheter. After several attempts to pull the crimped stent into the guide catheter, it became angiographically evident that the proximal edge of the stent had been longitudinally crushed while the supporting balloon had partially entered the guide catheter (Figure 1B). As a result, the stent was shortened in length by approximately 12 mm before deployment (Figure 1B). Due to this major proximal stent deformation, the operator failed to recapture the stent into the guide catheter. Subsequently, it became difficult to advance the balloon with the compressed stent from the LM into the LAD. After careful manipulation, the proximal edge of the stent could be placed at the ostium of the LAD, but the distal part of the lesion was not covered (Figures 1C and 1D). After stent deployment, the angiography showed a concentrated mass of unapposed struts at the proximal edge of the stent (Figure 1E). Postdilatation was performed at high pressure with a 3.5 mm non-compliant balloon and a 3 x 12 mm Taxus Element stent was placed on the residual LAD lesion. The final angiographic result was deemed acceptable (Figure 1F) and the patient remained well throughout the 8-month clinical follow-up.    

Discussion. Thus far, all published cases reported LSD after stent deployment. The present report is the first to describe longitudinal deformation of a new-generation stent before stent deployment. This distortion was the result of proximal stent edge crushing by the guide catheter during withdrawal of the balloon-stent system. A second important observation is that the deformation led to an inability to recapture the crimped stent into the guide catheter and severely limited balloon-stent maneuverability. This complication occurred in the setting of a complex procedure performed by a highly experienced operator. In our case, the crimped stent could initially not reach the target lesion due to significant residual stenosis despite balloon predilatations. On withdrawal of the crimped stent, deep engagement of the guide catheter led to a collision between the distal tip of the catheter and the proximal stent edge, resulting in stent blocking. One possible cause for such a resistance is when the distal tip of the catheter and the crimped stent are not coaxially oriented. However, this is usually not an issue in our experience. Unexpectedly, on attempts to remove the stent, the guide catheter crushed the proximal edge of the stent. The diagnosis was quickly evident on fluoroscopy showing a clear separation between the proximal balloon marker and the proximal stent edge. This proximal stent shortening was impressive and reached 35% of the initial length. Moreover, we found the same angiographic pattern as described previously of a focal increase in radio-opacity with an aspect of accordioned stent struts. After concluding that the stent could not be recaptured into the guide catheter, the operator experienced major difficulty while advancing the deformed stent. As a result, the stent was deployed in a location initially not intended. Another option considered by the operator during the intervention was to remove the guide catheter and the balloon-stent system in one step. However, this contained a strong risk of dislodging the stent from the balloon. As a consequence, the removal of a deformed free stent with reduced longitudinal strength would have been even more challenging. Furthermore, this last option implicates the loss of the coronary guidewire and can be inconvenient in specific settings, such as dissection or previous difficulty in lesion crossing. When choosing to deploy the deformed stent in a coronary artery, high-pressure postdilatation with a non-compliant balloon is of utmost importance as stent distortion may lead to severe underexpansion and malapposition, which are substrates for stent restenosis and thrombosis.

This case highlights an unreported aspect of the LSD issue by demonstrating that longitudinal deformation can occur also before stent deployment. The mechanism did not seem to differ from previous reports and involves a reduction in longitudinal stent strength. Although LSD appears to represent a rare complication in the current PCI practice, its occurrence can lead to serious adverse consequences. Since attention has been drawn recently to this issue, the report rate is likely underestimated and is expected to increase over time. We would urge operators and manufacturers to collect and report all cases of LSD in order to assess the exact incidence, the outcomes, and the real impact of this inconvenient complication on our clinical practice.

References

1. Hanratty CG, Walsh SJ. Longitudinal compression: a "new" complication with modern coronary stent platforms — time to think beyond deliverability? EuroIntervention. 2011;7(7):872-877.
2. Williams PD, Mamas MA, Morgan KP, et al. Longitudinal stent deformation: a retrospective analysis of frequency and mechanisms. EuroIntervention. 2012;8(2):267-274. 
3. Robinson AD, Schreiber TL, Sobh MA, Grines CL. Deformation, longitudinal shortening, and accordion of an ion stent. J Intervent Cardiol. 2011;24(6):493-495. 
4. Mamas MA, Williams PD. Longitudinal stent deformation: insights on mechanisms, treatments and outcomes from the Food and Drug Administration Manufacturer and User Facility Device Experience database. EuroIntervention. 2012;8(2):196-204.
5. Ormiston JA, Webber B, Webster MW. Stent longitudinal integrity bench insights into a clinical problem. JACC Cardiovasc Interv. 2011;4(12):1310-1317.

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From the Division of Cardiology, Centre Hospitalier Universitaire de Charleroi, Charleroi, Belgium. 

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted May 16, 2012, provisional acceptance given June 19, 2012, final version accepted June 27, 2012.

Address for correspondence: Adel Aminian, MD, Centre Hospitalier Universitaire de Charleroi, Division of cardiology, Bd Paul Janson 92, 6000 Charleroi, Belgium. Email: adaminian@hotmail.com