Optical Coherence Tomography Assessment of a Coronary Bare Cobalt Chromium Stent Deformed by the Removal (FULL TITLE BELOW)

FULL TITLE: Optical Coherence Tomography Assessment of a Coronary Bare Cobalt Chromium Stent Deformed by the Removal of an Entrapped “Jailed” Guidewire

ABSTRACT: A 64-year-old male with an ongoing acute coronary syndrome was treated percutaneously for a subtotal occlusion of a first diagonal branch. After predilatation of the diagonal, an important secondary branch was evident at the level of the subocclusion. A jailed wire was placed in this vessel, and stenting of the main diagonal branch was performed with a last-generation thin-strut bare cobalt-chromium stent. Conventional retrieval of the jailed wire was impossible, as the distal tip of the wire remained entrapped at the level of the stent. The strong pulling of the wire led only to a deep intubation of the guiding catheter with possible risk of dissection. Retrieval of the wire was finally possible with the support of an over-the-wire microcatheter. However, the stent, though still patent, appeared deformed. At a scheduled control angiogram 4 months later (while the patient was still asymptomatic), an optical coherence tomography (OCT) investigation of the stented segment confirmed the deformation of the stent. OCT showed a complete lack of stent struts on the side of origin of the secondary branch and an “overlap” or “accumulation” of several layers of stent struts on the other side. There were no signs of uncovered struts overall nor malapposition, and even the sites where multiple stent layers were visible were completely covered by neointimal hyperplasia. Despite the multiple layers of metal, the neointimal reaction was moderate and did not lead to a flow-limiting stenosis, thus the patient was further treated medically without the need for a new intervention.

J INVASIVE CARDIOL 2010;22:453–455

Key words: stenting; coronary interventions; complications; new techniques

_______________________________________________________ This case shows a potential risk associated with the “jailed-wire” technique for bifurcation lesions, and the possible damage to the stent when the operator gradually increases force in order to retrieve the entrapped jailed wire, as demonstrated by the optical coherence tomographic (OCT) findings at follow up.

Case Description

A 64-year-old male with known hypertension and a history of smoking suffered an acute coronary syndrome with minor elevation of his troponin levels and without acute electrocardiographic changes. He was sent to our catheterization laboratory for coronary angiography, which showed single-vessel disease with a subtotal occlusion of a first diagonal branch and thrombolysis in myocardial infarction (TIMI) flow 1 distally (Figure 1A). A percutaneous coronary procedure of this vessel was started after obtaining patient consent. After wiring the diagonal and performing a predilatation, an important secondary branch, originating just after the subocclusion, was evident. We decided to position a wire in this vessel before stenting the main diagonal branch (“jailed-wire” technique). We then placed, according to local practice, a last-generation thin-strut bare cobalt-chromium stent (diameter: 2.25 mm, length: 13 mm) in the diagonal branch over the ostium of the secondary vessel. After successful stenting, both vessels were open, without significant residual stenoses and with TIMI 3 flow (Figure 1B). When attempting to pull back the jailed wire, the very distal part of the radiopaque tip remained entrapped in the stent struts and its retrieval by simple pulling was impossible (Figure 1C). Indeed, by strongly pulling the wire, the only achievement was a deep intubation of the guiding catheter up to the left anterior descending (LAD)-diagonal bifurcation, with a high risk of dissection of the left main and proximal LAD. After placing a wire in the LAD to protect it, we positioned an over-the-wire microcatheter over the entrapped wire. We secured the distal tip of the microcatheter against the stent struts and once again, while further pushing the microcatheter to gain support, we pulled the wire. Finally, we succeeded in retrieving the wire without angiographic signs of dissection in the other vasculature. However, the segment of coronary artery previously treated with the stent had a result that appeared worse than before. Moreover, the stent appeared deformed, as by angiography without contrast it was more radiopaque in its proximal part than in its distal part (Figure 1D). We performed additional postdilatations with a noncompliant balloon and, noting the lack of dissections and a reasonable result, we accepted it (Figure 1E). We decided to schedule an angiographic control at 4 months in order to observe the reaction of the vessel to the stent deployed. The patient remained asymptomatic up to the control angiogram, which showed moderate hyperplasia at the level of the stented segment without a severe stenosis (Figure 1F). An intravascular OCT assessment of the stent, done with the M2x time domain-OCT catheter (LightLab Imaging, Inc., Westford, Massachusetts) during continuous low-flow low-pressure (3 ml/sec, 150 psi) contrast flushing from the guiding catheter via an injector pump in order to remove the blood and to allow visualization of the stented vessel wall during OCT pullback, confirmed the angiographic findings and offered additional details (Figure 2). The stent appeared normal distally to the bifurcation (Figure 2A), with its expected cylindrical shape, while proximally to the bifurcation the deformation of the stent was evident, with a complete lack of stent struts on the side of origin of the secondary branch and an “overlap” or “accumulation” of several layers of stent struts on the other side (Figures 2D–2G). More proximally, the stent was again cylindrical in shape, but still with “accumulation” of stent struts on one side (Figures 2H and 2I). Interestingly, the stent length measured with OCT was 9.6 mm, more than 3 mm shorter and over 25% shorter than the nominal stent length (13 mm). These images could also explain what happened during the procedure. While pulling the jailed wire, we pulled some stent struts away from the vessel wall at the level of the bifurcation and, while pushing the microcatheter, we collapsed or crushed part of the proximal struts together, thus explaining how the stent became shorter. The multiple balloon inflations performed inside the boundaries of the stent after retrieval of the entrapped wire led to a partial “crushing” of the mid part of the stent on one side of the vessel wall. Interestingly, there were no signs of uncovered struts overall or malapposition, and even the sites where multiple stent layers were visible were completely covered by neointimal hyperplasia. Since the patient was asymptomatic and the OCT provided reassuring information, we decided to treat him medically.

Discussion

This case shows a potential risk associated with the “jailed-wire” technique for bifurcation lesions, and the possible damage to the stent when gradually increasing force in order to retrieve the entrapped jailed wire, as demonstrated by the OCT findings at follow up. Several techniques and devices have been proposed to retrieve jailed guidewires from coronary stents, but the general concept was always substantially similar: the use of small-caliber devices pushed over the jailed wire to allow selective force retrieval by pushing the wire back into the device itself. Among the devices proposed, there were standard rapid-exchange low-profile balloons, over-the wire balloons, microcatheters and specific devices mainly dedicated to chronic total occlusions such as the Tornus device (Asahi Intecc, Aichi, Japan). The additional finding of this case report was the use of OCT to try to understand the specific way the stent was deformed by the selective force applied using one of these devices to retrieve the jailed guidewire. OCT, due to its extremely high resolution, allows a better understanding of the performance of metallic stents in the coronary circulation, as it permits a clear visualization of every single strut. This “strut-level” analysis leads to information more detailed and more adequate than traditional techniques such as standard angiography and intravascular coronary ultrasound. These techniques are indeed limited by a resolution that is at least 10 times lower than the one of OCT. In our case report, OCT performed during the control angiography 4 months after stent implantation provided a more comprehensive understanding of the events that occurred during the index procedure.

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From the University Medical Center Utrecht, The Netherlands. The authors report no conflicts of interest regarding the content herein. Manuscript submitted February 16, 2010, provisional acceptance given March 10, 2010, final version accepted March 29, 2010. Address for correspondence: Dr. Pierfrancesco Agostoni, MD, PhD, University Medical Center Utrecht Department of Cardiology, Heidelberglaan 100, Utrecht, 3584 CX, Netherlands. E-mail: agostonipf@gmail.com