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Ann Thorac Surg 2007;83:1530-1532
© 2007 The Society of Thoracic Surgeons
a Department of Cardiothoracic Surgery, Royal Melbourne Hospital, University of Melbourne, Australia
b Department of Cardiology, Royal Melbourne Hospital, University of Melbourne, Australia
Accepted for publication December 29, 2006.
* Address correspondence to Dr Luthra, Department of Cardiothoracic Surgery, 2 North, Royal Melbourne Hospital, Grattan Street, Parkville, Melbourne, Victoria 3050 Australia (Email: suviteshluthra{at}yahoo.com).
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A 50-year-old man, who was hypertensive, diabetic, and a smoker, presented with chest pain and diaphoresis to the emergency department in 2002. An electrocardiogram revealed ST segment elevation of more than 0.2 mV in the lateral leads. Cardiac enzymes at 6 hours were significantly elevated (troponin T-94.75 ug/L, lactate dehydrogenase-1150 U/L). Angiography done after stabilization revealed a 80% proximal left anterior descending artery (LAD) lesion, which was stented with a 2.50-mm x 18-mm, 3.00-mm x 18-mm CYPHER (Cordis, Miami Lakes, FL). He was commenced on antiplatelet therapy.
The patient presented 4 years later with progressively increasing exertional angina of 6 months’ duration. Repeat angiography revealed in-stent stenosis and areas of extensive aneurysmal dilatation in relation to the stent (Fig 1). The lesions were considered unsuitable for percutaneous intervention.
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Meta-analysis of available studies has shown vastly superior results with DES compared with bare metal stents for restenosis (7.6% versus 36.8%) and adverse cardiac events (10.1% versus 19.9%). Acute clopidogrel withdrawal has been a cause for concern recently. There is a 10% to 15% absolute benefit in reduced revascularization for a 0.5% to 2% absolute risk of late thrombosis, a significant morbid event associated with infarctions and death [1].
In-stent restenosis is associated with allergies to nickel and molybdenum. The methacrylate coating induces smooth muscle cell apoptosis and failure of recruitment of neointimal progenitor cells for endoluminal coverage. The absence of this neointimal proliferation probably accounts for improved restenosis rates long after sirolimus has eluted away. The effects of inflammation and delayed healing in the long term are unclear.
The United States Food and Drug Administration (FDA) approved the sirolimus stent in April 2003. In October 2003, it passed an advisory directive for physicians on the adverse events associated with sirolimus stents based on 290 reports of thrombosis occurring 1 to 30 days after implantation [2]. In more than 50 reports, including some deaths, the cause was possibly a hypersensitivity reaction, although the mechanism was unclear at the time. As a condition of approval, FDA required Cordis to conduct a 2000-patient postapproval study and continue evaluating patients from ongoing clinical trials to assess the long-term safety. Meta-analyses of later randomized clinical trials failed to show an increased risk of other adverse events related to DES [3, 4].
Studies as early as 2001 document synthetic polymer-induced chronic low-grade inflammation, poor healing, and intraintimal hemorrhage with DES. Virmani and colleagues [5] documented a localized hypersensitivity reaction consisting of fragments of polymer, T cells, and eosinophils in a patient who died 18 months after CYPHER stent implantation. They implicated the nonerodable polymer because sirolimus is no longer present in the vessel wall after 60 days and its inherent antiinflammatory properties would suppress accumulation of inflammatory cells.
In 2006, the FDA identified 14 cases of CYPHER and 3 of TAXUS (Boston Scientific, Natick, MA) of probable or certain DES-induced hypersensitivity syndromes from Manufacturer and User Device Experience Center database, cases seen by Research on Adverse Drug Events and Reports project co-investigators, and published cases [6]. These included four deaths from acute stent thrombosis. Intrastent eosinophilic infiltrates and poor intimal healing were seen as late as 18 months. Concomitantly placed bare-metal stents were not associated with these findings. No coronary dilatation or rupture was reported.
The models of response of human endothelium to stents are calculated extrapolations of the studied responses in pigs and rabbits. The accepted standards of safety for DES are 90-day and 180-day animal models, which potentially overlook the long-term effects. Based on the species’ lifetime, essential temporal differences exist in vascular healing patterns between humans and the studied animals. Compared with normal vessels of experimental animals, the stents cover calcified, fibrotic, and relatively hypocellular plaques in humans. These plaques must recruit cells from other remote areas of the arterial wall for luminal cover. Furthermore, late chronic inflammatory responses may evolve for up to 4 years after DES implantation in human plaques.
The prevention of restenosis in recent clinical trials of DES for 2 to 3 years in humans represents a nearly absent or incomplete phase of inflammation and healing [7]. We see this case report as part of a much larger picture that is beginning to emerge only now as the patients who received DES pass into the later, yet unclear, stages of vessel wall reactivity that involve persistent inflammation, weakening, and erosion. It may still be too early to tell whether coronary artery aneurysm formation in association with DES is a sporadic or a potentially systemic problem.
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