From the *Department of Internal Medicine, University of Illinois College of Medicine at Peoria, Peoria, Illinois; the §Department of Cardiology, Baylor College of Medicine, Houston, Texas; and £Heartcare Midwest, OSF St. Francis Medical Center, Peoria, Illinois. The authors report no conflicts of interest regarding the content herein. Manuscript submitted February 4, 2009, provisional acceptance given March 16, 2009 and final version accepted May 7, 2009. Address for correspondence: Sudhir Mungee, MD, FACC, Heartcare Midwest, OSF St. Francis Medical Center, 5405 North Knoxville Ave, Peoria, IL 61614. E-mail: firstname.lastname@example.org
J INVASIVE CARDIOL 2009;21:E180-E183 Case Presentation. A 63 year-old male with a past medical history of coronary artery disease (CAD) with left anterior descending (LAD) artery stent placement in 2005, hypertension, non-insulin-dependent diabetes, hyperlipidemia, morbid obesity and obstructive sleep apnea presented with a non-ST-elevation myocardial infarction. He underwent coronary angiography and a total occlusion of the mid-right coronary artery (RCA) was found. Post-balloon angioplasty of the mid-RCA, several attempts to advance a stent were unsuccessful due to vessel tortuosity and calcification (Figure 1). The procedure was complicated by dissection of the proximal RCA, likely guide-induced, which was treated with angioplasty and stenting using a 2.5 x 18 mm Xience everolimus-eluting stent (Abbott Vascular, Abbott Park, Illinois). The patient remained stable, his medications were optimized and he was discharged home. The patient was readmitted 2 months later with exertional angina and exertional dyspnea that was refractory to medical therapy. Coronary angiography revealed a 90–95% mid-RCA culprit lesion. After discussion with the patient, the decision to undergo another percutaneous attempt of revascularization was made. The small aortic root and the takeoff of the RCA were felt to be unsuitable for use of a more aggressive Hockey stick or an Amplatzer guide (AGA Medical Corp., Plymouth, Minnesota), thus a JR4 guiding catheter (Medtronic, Inc., Minneapolis, Minnesota) with a long Prowater wire (Abbott Vascular) was used to cross the culprit lesion. An over-the-wire system was used in the event that an extra-support wire exchange was needed due to the tortuous anatomy. Predilatation of the mid-to-distal RCA was performed using a Maverick 2.5 x 12 mm balloon at 6 atmospheres (atm) pressure and thrombolysis in myocardial infarction (TIMI)-3 flow was noted. Next, a 2.5 x 12 mm Xience everolimus-eluting stent was planned for deployment at the sites of angioplasty in the mid-to-distal RCA. However, due to the previously placed proximal RCA stent, it was difficult getting this stent to pass through the previous stent. During pullback of this stent, it stripped off the balloon. Two angiographic views, straight anteroposterior (AP) and shallow left anterior oblique (LAO), localized the undeployed stent within the old stent (Figure 2). The balloon was checked outside the body for absence of any struts. A Maverick 2.0 x 15 mm balloon was advanced over the wire through the undeployed stent. An attempt to advance or retract the undeployed stent struts with the use of the small balloon was unsuccessful, likely due to the fact that these struts were in friction with the previously deployed stent at this location. This stent was then deployed within the previous stent at 16 mmHg pressure for 30 seconds and postdilated with a noncompliant Quantum 2.5 x 15 mm balloon (Boston Scientific Corp., Natick, Massachusetts) at 14 atm for 30 seconds, with a final MLD of 2.75 mm (Figure 3). Final angiography showed excellent results with TIMI-3 flow (Figure 4) and stenting of the mid and distal RCA lesions was then aborted. The patient denied chest pain and his electrocardiogram remained normal. He was observed overnight, continued his aspirin and clopidogrel, and was discharged in stable condition. Discussion. A “stripped stent”, or dislodgment, is a rare, but feared, complication among interventionalists. In 2005, Brilakis et al reported 38 cases of stent loss out of 11,773 PCI procedures, which correlated to an incidence of 0.32%.1 Other incidence rates of dislodgement of a stent from the delivery balloon have shown to range between 0.35–8.4% among various studies.2,3 In 1998 Cantor et al showed that 9 of 108 cases of failed stent deployment in a series of 1,303 percutaneous coronary intervention (PCI) procedures were due to the inability to pass a stent through a previously deployed stent. The risk factors causing a failed procedure in this study included the large number of manually crimped stents and previous stent suboptimal deployment or deployment into an angulated vessel segment that increased the risk of the struts of the 2 stents opposing each other.4 Decreased use of manually crimped stents and use of more flexible, premounted stents in addition to improvement of stent technology and operator experience may be the cause of the decline in the incidence of stent dislodgement. Coronary risk factors for stripped stents include higher degrees of calcification, tortuous vessels with proximal or moderate-to-severe angulation, prior coronary artery bypass graft (CABG) surgery and the passage through primary, recently placed or nonendothelialized stents. An analysis by Kammler, et al demonstrated that the target coronary vessel may influence the incidence of stent loss. In their report of 36 cases of stent loss, the RCA had stent loss in 64% of patients, the left anterior descending (LAD) artery in 19%, the left circumflex in 11%, and 3% in both the left main artery and a vein graft.5 Technical risk factors for stripped stents include manually crimped stents, poor support of the guiding catheter, increased rigidity of the stent and direct stenting without complete predilatation.1 Previously described examples of complications during placement of stents include dislodgement of the stent within the catheter when negative pressure is applied resulting in detachment from the balloon, allowing it to wedge into the distal tip of the guiding catheter,6 and inadvertently allowing the stent to readvance as the catheter sheath is pulled back.7 Stent migration, as with the currently discussed case, can happen if a previously placed stent in the proximal portion of the coronary vessel strips the newer stent from its delivery balloon. Complications associated with dislodged stents include increased risk for subacute thrombosis at the site of dislodgement, bleeding and death. Dislodged stents have also been associated with myocardial infarction, cerebrovascular embolic events and higher rates of emergency CABG. Methods for prevention include predilatation of the stenosis prior to stent placement, removing the stent, wire and guide as a unit, and avoidance of excessive force when resistance is encountered during stent withdrawal.1 Slight bending of the stent to allow more flexibility in a tortuous vessel can be done to match the patient’s anatomy.6 Recognizing that a stent has dislodged from the balloon may be difficult, but locating the stent after it has dislodged may be even more so. The stent may be found as a radio-opacity proximal to a tortuous segment in an artery. When a stent is first noticed to have been detached from the balloon, the goal of treatment is to either retrieve or deploy the stent to reduce any ischemic complications without causing vessel trauma. The method chosen depends on several factors including the position of the stent in the coronary tree, the integrity of the stent, persistence of a wire or balloon inside the stent and the vessel size. Stent Retrieval. Retrieval of the dislodged stent includes the use of several different tools and these can be used in combination. Gooseneck or end-snares are most commonly used and contain multiple wire loops at 90 degrees to each other that create a “lasso” effect for retrieval. The small balloon technique is used for lost stents still on a guidewire and involves placing the balloon distal to the stent and then inflating. The balloon is then pulled toward the guide catheter and the stent, balloon and catheter are removed as a whole.8 A study by Bolte et al showed that during 257 rescue attempts, the gooseneck snare and the small-sized balloon technique had the best success rates compared to several other retrieval techniques.9 A 2-wire technique can be used whereby a second guidewire is threaded parallel to the first one across the stent. This guidewire can either be entangled in the first wire distal to the stent, or it can be passed through the struts of the undeployed stent. Both guidewires are then pulled back together, retrieving the stent. Biliary forceps, a basket retrieval device and a Cook retained fragment retriever can only be used in the aorta and femoral and iliac arteries secondary to their larger size in relation to the coronary arteries.1 Germane to this discussion, if the stripped stent is in close proximity to a previously deployed stent, such as in our case, it may be hazardous to try any of the above retrieval methods, as there is a risk of ensnaring or entangling the old stent during the process. Most of the data on short- and long-term outcomes of stent loss during coronary stenting come from studies or reports from the bare-metal stent (BMS) era.6,7,9,13 The introduction and widespread use of drug-eluting stents (DES) presents a hitherto unencountered challenge to the interventionalist planning a stent-retrieval approach. The struts of a previously placed DES that is in proximity to the dislodged stent may hamper retrieval attempts, as illustrated in this case. This is particularly important when the old stent is not well endothelialized, as can be expected from a recently placed DES. Stent Deployment. Several methods to successfully place a stripped stent have been reported in the literature. The use of an overlying stent deployment or crushing technique has been found to be successful in several studies. Hussain et al described a case where they had an undeployed stent detached from the balloon, but still on the wire. They used a second “buddy wire” to pass through the center of the stent along with the primary wire. An angioplasty balloon was then threaded onto the buddy wire to the site of the stent, and the stent was then deployed.10 The use of an unexpanded delivery balloon to push the stent to the desired location distally before deployment has previously proven successful.11 Because of the higher risk of restenosis, critical locations such as the left main and proximal LAD arteries should be avoided when placing a dislodged stent.1 One rare complication of coronary stent deployment includes coronary artery aneurysm formation. In an analysis by Aoki et al, the reported incidence of coronary aneurysms in DES was 0.2–2.3%, and was found to have occurred between 3 days to 4 years after deployment. The incidence of aneurysm formation with DES and BMS were 1.1% and 0.8%, respectively, which favors the use of BMS. Speculated differences noted between the two include inflammatory reactions in response to implanted DES and complex allergic reactions to the drug or polymer of the DES. Incomplete endothelialization could be a precursor to aneurysm formation.12 Given the fact that there is a small statistical difference between DES and BMS in terms of coronary artery aneurysm formation, and that its occurrence is rare, it is unknown whether deploying a DES at the site of an incompletely endothelialized, previously placed DES will increase the risk of aneurysm formation. Stent embolization is a concern in cases of detached stents and typically occurs when the stent cannot cross the lesion. In a retrospective study evaluating failure of stent deployment, Nikolsky et al found stent embolization occurred in 10 out of 151 patients. Eight of the 10 resulted in distal embolization to the lower extremities, 1 stent was wedged in the left main coronary artery and eventually pushed to the mid-LAD and compressed against the wall of the vessel with a balloon, while in the remaining case, the stent was undetectable.13 Stents can embolize to the distal portion of the artery, the opposite coronary artery, or the systemic circulation.2 Another retrospective study analyzed 411 stent embolizations in 387 patients out of 20,298, in which 1 patient had a stent embolized to the posterior mitral valve leaflet.9 Retrieval devices as previously described can be utilized first if the stent is not in a high-risk location, but surgical removal may be necessary. If the stent embolizes into a small arterial branch, it may not need to be treated, as such occurrences appear to have a benign course. The use of intravascular ultrasound has been shown to be helpful in confirming the location of a guidewire in relation to a dislodged stent and also ensures adequate expansion after balloon deployment.14 The incidence of stent embolization has decreased over the last decade to 0.27–0.33%.1,3,15 Advances in stent design to limit this complication include edgeless struts, thinner struts allowing a lower profile and more flexibility, balloons that are tightly wrapped to decrease the profile, and tighter crimping of the stent onto the balloon with proximal and distal pillowing of the balloon to protect the stent edges during withdrawal or advancement. Conclusions. With an undeployed stent inside of a DES that was placed 2 months prior within the ostium of the RCA, retrieval by a snare technique was deemed too unsafe secondary to the risk of also snaring the original stent that was partially endothelialized. Instead of using the approach of a buddy wire, a long balloon was placed through the undeployed stent on the unremoved guidewire to deploy the stent over the existing stent, leaving TIMI-3 flow in the RCA. With respect to longer-term complications of our procedure with the possibility of coronary artery aneurysm formation at the site of stent deployment, the literature is unable to show if there is an increased risk in our patient.
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