Unrecognized Stent Embolization Causing Recurrent Chest Pain

Stent embolization is a relatively rare but serious complication of coronary stenting. Early reports identified hand-crimped and coiled stents as being particularly prone to embolization.¹ In addition, certain procedural and lesion characteristics have been identified as being associated with stent embolization. Among these are failure to cross a lesion with subsequent withdrawal of an undeployed stent into the guiding catheter, angulated or tortuous lesions, moderate or severe calcification, distal location and attempting to pass a stent through a previously deployed stent.^2,3 Despite dramatic advances in stent design and factory premounting, stent embolization has not been eliminated in contemporary practice. Numerous case reports and series have described percutaneous means of safely and effectively retrieving embolized stents at the time of the index procedure. The most commonly employed methods include low-profile angioplasty balloons, gooseneck snares, myocardial biopsy forceps and “sandwiching” the embolized stent against the vessel wall with a properly deployed stent.^4,5 We report a case in which an embolized stent was not appreciated during the index procedure. The patient subsequently developed recurrent chest pain, underwent repeat angiography, and was found to have a thrombus-filled undeployed stent that was compromising coronary flow. Case report. A 62-year-old male was self-referred to our institution for a second opinion regarding chest pain. Six months prior to presentation at our institution, he had suffered an acute anterolateral myocardial infarction. Angiography revealed high-grade stenoses in the ramus intermedius (RI) and mid-left anterior descending (LAD) coronary arteries. The RI was thought to be the culprit lesion and was directly stented with a 2.5 x 8 mm ACS Multi-Link coronary stent (Guidant Corp., Indianapolis, Indiana). The patient underwent a staged intervention in the LAD 3 days later with a 2.0 x 8 mm ACS Multi-Link stent (Guidant). The left ventricular systolic function was reportedly normal by echocardiography. Approximately 4 weeks after the index event, he developed congestive heart failure and severe mitral regurgitation and underwent mitral valve replacement with a mechanical prosthetic valve. The patient had an uneventful postoperative course and was discharged on warfarin. Subsequently, the patient developed recurrent chest pain and palpitations for which he was started on amiodarone. The symptoms continued unabated, and repeat angiography was performed 5 months after the initial LAD stenting procedure. The patient was informed that he had a restenotic lesion within the previously placed LAD stent. He subsequently sought a second opinion at our institution. Review of the angiogram from the outside institution revealed a filling defect in the mid-LAD at the site of the prior intervention. The lesion was not consistent with in-stent restenosis and was felt to represent a thrombosed, undeployed stent. Contrast was clearly seen outlining a filling defect in the middle of the LAD. Repeat angiography at our institution redemonstrated the mid-LAD filling defect (Figures 1A and B). A 0.014 inch S’port™ guidewire (Guidant) was advanced past the lesion into the distal LAD with minimum difficulty. Initial IVUS using a 6 Fr Atlantis™ SR Pro Coronary Imaging Catheter (Boston Scientific Corp., Natick, Massachusetts) confirmed the presence of an unexpanded stent (Figure 2). A 2.0 x 20 mm OpenSail^® angioplasty balloon (Guidant) was used to crush the undeployed stent against the vessel wall. A 2.5 x 13 mm Multi-Link Pixel^® stent (Guidant) was then deployed to “sandwich” the undeployed stent against the vessel wall (Figures 3A and B). Correct and complete apposition of the stent against the vessel was confirmed with repeat IVUS imaging (Figure 4). During the procedure the patient was treated with 6,000 U of intravenous heparin in addition to aspirin and clopidogrel. Warfarin was resumed for his prosthetic heart valve. The postprocedural course was uneventful. The patient has remained free from chest pain for 6 months since the procedure. Discussion. Our report of an embolized stent is unique for a number of reasons. First, it had been embolized for several months prior to our procedure. Most embolized stents are addressed during the index procedure. Second, the stent was likely thrombosed. Though we did not demonstrate the actual presence of thrombus by removing the stent, the stent was filled with non-opacifying material, which is unlikely to be anything other than thrombus. The thrombus had formed despite the patient being on systemic anticoagulation with warfarin for his prosthetic heart valve. It is also noteworthy that the patient had presented with heart failure and mitral regurgitation following the index stent embolization and had undergone surgical valve replacement without recognition of the embolized stent by the treating physicians. Lastly, it is remarkable that, though the stent had thrombosed, the LAD itself had not and remained patent. The true incidence of stent embolization is likely underestimated due to reporting bias and cases such as the one currently under consideration in which embolization was not appreciated. Early studies found a 1–3% incidence of embolization.^6–8 More contemporary series utilizing premounted stents demonstrate a much lower incidence, ranging from 0.27–0.33%.^4,9 Additionally, many currently available stents are poorly visualized on fluoroscopy before and after deployment. Goldberg et al. describe a case in which stent embolization was discovered only after IVUS examination of the target lesion failed to demonstrate the presence of a stent.¹⁰ Short- and long-term followup studies show that patients with coronary stent embolization have low event rates provided the stent can be retrieved, deployed or effectively “sandwiched” against the vessel wall. Embolized stents that remain within the coronary circulation, however, are associated with high event rates and poor long-term outcomes.¹⁵ If an embolized stent is unable to be effectively treated percutaneously, consideration should be given to coronary bypass grafting. In the case of central or peripheral embolization, reported event rates are very low,^4,13,15,16 although there have been isolated case reports of limb ischemia.¹¹ In general, asymptomatic peripheral stent embolization may be treated conservatively. Though the incidence of stent embolization is relatively low, given that more than 500,000 percutaneous coronary revascularizations are performed every year in the United States,¹² and that stents are used in 60–80% of these procedures,¹³ the absolute number of embolic events is far from negligible. The interventionalist must be aware of this potential complication and the factors which predispose to it. Stent embolization is not always immediately apparent, particularly with fluoroscopic imaging. Therefore, a high index of suspicion must be maintained in appropriate circumstances and, if necessary, IVUS confirmation of stent deployment should be obtained. Our case illustrates that even a chronically embolized and thrombosed stent could be successfully managed by crushing it with another stent against the wall of the artery. This allowed us to alleviate the functional stenosis and relieved the patient’s ischemic symptoms.

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