Vascular Healing 4 Years After the Implantation of Sirolimus-Eluting Stent in Humans
A Histopathological Examination
A 60-year-old male patient with coronary disease was included in the “First-in Man” study1 and received a single sirolimus-eluting stent (SES, fast release) in December 1999 to treat a 90% diameter stenosis lesion located in the proximal right coronary artery (RCA). The patient had mild to moderate (<50% diameter stenosis) obstructions in the left anterior descending and left circumflex arteries. Coronary angiography and intravascular ultrasound (IVUS) revealed minimal neointimal growth in the midstent region at 4 months, 1 year, and 2 years after implantation. The patient underwent aortic and mitral valve replacement without complication 3 years after SES implantation. Left ventricle ejection fraction was 22%. He had a cardiac arrest out of the hospital in January 2004 (4-year follow-up). The patient was resuscitated but suffered severe cerebral damage. Postarrest angiography showed a widely patent SES in the RCA with a % obstruction volume of 19% by IVUS with minimal intimal hyperplasia by IVUS (Figure 1). The patient developed brain death and died. At necropsy, there was a 60% cross-sectional area of luminal narrowing of the RCA proximal to the stent. The stented segment was widely patent and well healed. Scanning electron microscopy of the proximal stent showed >95% of stent surface endothelialized (Figure 2). Light microscopic sections of the distal portion of the stent demonstrated a thin neointima consisting of smooth muscle cells and macrophages (predominately KP1-positive cells) in collagen-rich matrix. Approximately 75% of stent struts were covered by a thin type I collagen-rich neointima, and occasional calcific foci were present in neointima. The remaining 25% of struts were deeply embedded in the necrotic core of the plaque without associated inflammation. The RCA distal to stent was widely patent (<25% narrowing). The left anterior descending artery showed an acute plaque rupture and luminal thrombus in the proximal arterial segment. Atherosclerosis progression was noted in the left circumflex artery and posterior descending artery. The bioprosthetic aortic valve had a small fibrin thrombus deposition at the base of the right coronary cusp.
The editor of Images in Cardiovascular Medicine is Hugh A. McAllister, Jr, MD, Chief, Department of Pathology, St Luke’s Episcopal Hospital and Texas Heart Institute, and Clinical Professor of Pathology, University of Texas Medical School and Baylor College of Medicine.
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