Rotational Ablation of an Unexpandable Sirolimus-Eluting Stent

The use of rotational atherectomy to ablate part of a metallic stent has been very limited, mainly because there are a small number of candidates for this type of procedure,1–7 but probably also because of the concern regarding the size and fate of the metallic particles that are produced. This case report describes the successful rotational ablation of a focally unexpandable Cypher stent due to a coronary constriction ring twelve months after the initial stent deployment Case Report. A 77-year-old patient presented with a five-month history of exertional angina with worsening symptoms over the last month. The patient had a history of hypertension and a five-year history of diabetes mellitus treated with oral medication. At cardiac catheterization of the left ventricle revealed normal wall motion. The proximal left anterior descending artery had a long calcified lesion with 80% stenosis. The right coronary artery was occluded at the proximal and mid-third (Figure 1A), with an additional occlusion proximal to the posterior descending artery, but the calcification was not as prominent as in the left anterior descending artery. Angioplasty of the left anterior descending artery was successfully performed with a cutting balloon, followed by the deployment of a 3 x 33 mm Cypher drug-eluting stent (Cordis Corp., Miami Lakes, Florida). The right coronary artery was opened successfully and predilatation was performed with a 2.5 x 20 mm Extensor balloon (Medronic, Santa Rosa, California) at 10 atmospheres. The balloon seemed to be fully expanded except for a mild localized compression. No further dilatation was performed. When a DES stent was deployed (Cypher, Cordis 3 x 24 mm), a focal severe underexpansion of the balloon and stent remained, even at a pressure of 20 atmospheres (Figure 1B). Despite dilatations with a 3 x 8 mm Quantum™ balloon (Boston Scientific, Maple Grove, Minnesota) and a 3.5 x 8 mm Crossail ballon (Guidant Corp., Santa Clara, California) to 25 atmospheres, an 80% stenosis remained (Figure 1C). The patient was discharged on aspirin and clopidogrel. The patient continued to have symptoms to a lesser degree. A thalium 201 stress test showed ischemia of the inferior wall. Twelve months after the first angioplasty, the patient underwent a coronary angiogram which showed an excellent result at the left anterior descending artery and an open right coronary artery with a focal stenosis at the location of the unexpanded stent (Figure 2A). The distal artery was patent, with stenoses of 75% and 90%. The patient was given abciximab and rotational atherectomy was performed with a 1.75 mm burr at 150,000 to 155,000 revolutions per minute. The stenosis was crossed after a total duration of rotational ablation of 180 seconds, with maximum duration of each advancement in a “pecking” motion of less then 18 seconds (Figure 2B). The patient experienced no pain, no arrhythmias and no signs of no-reflow. The stenosis was dilated with a Quantum 3 x 8 mm balloon (Boston Scientific) at 18 atmospheres. An intracoronary ultrasound examination showed only two or three stent struts and the presence of a 2,000 arc of calcium at the site of the stenosis (Figure 3). A 3.5 x 18 mm Taxus drug-eluting stent was deployed (Boston Scientific) at 12 atmospheres, with only mild underexpansion (Figure 2C). Additional angioplasty was performed at the distal part of the vessel. The patient’s CK and troponin remained in the normal range, and he was discharged on aspirin and clopidogrel. Discussion. Severe stent underexpansion is a problem that can usually be solved with high-pressure balloon dilatation. Occasionally, this is not sufficient and one is left with a severely underexpanded segment of the stent. Depending on the selection of patients, even with direct stenting, severe focal stent underexpansion is a rare event.¹ This, and even lesser degrees of underexpansion are associated with subacute occlusion and restenosis. Limited strut ablation has been used to provide access to jailed side branches,^4–8 but rotational atherectomy has only recently been used to perform lengthwise ablation on the stent struts and constraining wall. The reported experience for this type of procedure is very small;^1–3 most of the experience is related to the use of rotational atherectomy to ablate the hyperplastic tissue of in-stent restenosis, with no intention to reach the stent struts.⁹ The use of rotational atherectomy to ablate the struts of a polymer-covered drug-eluting stent has not been reported, though it is of obvious relevance in the current era and may involve special considerations. A recent editorial¹⁰ outlined the problems encountered from extensive ablation of stent struts, which include heat generation, particle embolization, platelet activation, and potentially, rotablator burr trapping distal to the stenosis. For this case, we selected a medium-sized burr and gently advanced to avoid the potential danger of burr trapping distal to the stenosis, as is described when small-sized burrs are used in undilatable severe stenoses.¹¹ The technique of a “pecking” type of short duration, forward burr advancement that we performed may reduce heat generation and the number of particles per unit time. The particle size generated is not known, but in our case, there was no evidence of significant distal embolization in terms of pain or enzyme elevation. In an in vitro study of stent ablation, the particle size of slotted stents was less then 1.7 mm,¹² but the type and size of particles of polymer-covered stents is not known. The patient was given abciximab prior to the procedure in order to minimize the platelet effect.¹³ We avoided ablation of the stent during the initial angioplasty procedure because we were concerned about the effects of ablation on the local release of the drug, exposure of the polymer cover, and additional platelet activation that occurs in a two-vessel angioplasty procedure. Ablation of the Cypher stent proved to be safe, at least at a later date. Despite the presence of severe stent underexpansion, but apparently good apposition of the struts to the vessel wall after such a high deployment pressure, it is impressive that no occlusion or significant hyperplastic response occurred. In conclusion, this case demonstrates the feasibility and apparent safety of “stentablation” in a drug-eluting stent late after its implantation.

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