Published Online
on June 29, 2009

A more recent version of this article appeared on July 14, 2009

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Submitted on August 3, 2007
Accepted on May 4, 2009

Comparison of Inflammatory Response After Implantation of Sirolimus- and Paclitaxel-Eluting Stents in Porcine Coronary Arteries

Gregory J. Wilson MD^*, Gaku Nakazawa MD, Robert S. Schwartz MD, Barbara Huibregtse DVM, Bradley Poff DVM, Thomas J. Herbst PhD, Donald S. Baim MD, and Renu Virmani MD

From the Department of Laboratory Medicine and Pathobiology, University of Toronto, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada (G.J.W.); CVPath, International Registry of Pathology, Gaithersburg, Md (G.N., R.V.); Minnesota Cardiovascular Research Institute, Minneapolis Heart Institute Foundation, Minneapolis (R.S.S.); and Division of Clinical Sciences, Boston Scientific Corp, Natick, Mass, and Plymouth, Minn (B.H., B.P., T.J.H., D.S.B.).

^* To whom correspondence should be addressed. E-mail: gregory.wilson{at}sickkids.ca.

Background—Although both sirolimus (CYPHER) and paclitaxel (TAXUS) drug-eluting stents have demonstrated efficacy and safety in clinical trials, human autopsy data have raised concerns about long-term healing and the potential for local inflammatory reactions.

Methods and Results—Overlapping stents (CYPHER drug-eluting stents, Bx SONIC bare metal stents, TAXUS drug-eluting stents, and Liberté bare metal stents) were implanted in noninjured coronary arteries of 58 domestic swine. Histopathological evaluation of proximal, overlapped, and distal stented segments was determined with emphasis on inflammation at 30, 90, and 180 days. Circumferential granulomatous inflammation in all stented segments was defined as inflammation consisting of macrophages, multinucleated giant cells, lymphocytes, and granulocytes, including many eosinophils, adjacent to almost all struts. Circumferential granulomatous inflammation was more prevalent in CYPHER (9 of 23, 39%) compared with TAXUS (1 of 21, 5%; P=0.01) and control bare metal stents (0 of 44) in the combined 90- and 180-day cohorts. Only CYPHER specimens showed marked adventitial inflammation (P=0.0025) and fibrosis (P=0.0055) accompanied by extensive remodeling. Fibrin deposition within neointima and medial smooth muscle cell death were greater (both P<0.001) in TAXUS than CYPHER at 30 days, with more fibrin in TAXUS than CYPHER through 90 days (P<0.05).

Conclusions—Although these data cannot be directly extrapolated to humans, the high prevalence in this porcine model of diffuse granulomatous inflammation seen with CYPHER stents, persisting at 180 days and associated with extensive remodeling of the artery, and persistent para-strut fibrin deposition with TAXUS stents emphasize the need for further investigation of biocompatibility with these and other novel combination drug/polymer drug-eluting stents.

Key words: angioplasty • coronary disease • inflammation • pathology • stents

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