DES Show More Neoatherosclerosis Than BMS Over 4 Years

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Following stent implantation, neoatherosclerosis develops earlier and to a greater degree inside drug-eluting stents (DES) than bare-metal stents (BMS), according to an optical coherence tomography (OCT) analysis published online June 22, 2012, ahead of print in the American Journal of Cardiology. Beyond 48 months, however, both stent types show lipid-laden plaque.

Researchers led by Ik-Kyung Jang, MD, PhD, of Massachusetts General Hospital (Boston, MA), investigated the incidence and tissue characteristics of neoatherosclerosis within implanted stents at different time points using OCT. For the analysis, 138 stents from 124 patients were classified into 3 groups according to length of follow-up:

• Early phase (< 9 months): 25 BMS and 27 DES
• Intermediate phase (9-48 months): 18 BMS and 43 DES
• Delayed phase (≥ 48 months): 13 BMS and 12 DES

All data were from patients enrolled in the international Massachusetts General Hospital OCT registry.

DES Show More Plaque in Early, Intermediate Phases

In both the early and intermediate phases, a greater incidence of lipid-laden plaque was found in DES than in BMS, with a greater proportion of lipid within the neointima (table 1).

Table 1. Neointima Characteristics According to Follow-up Phase

Quantitative tissue property analysis did not show any differences between the BMS and DES in the early phase. But in the intermediate phase, signal attenuation was greater in the DES group, suggesting early changes in neointimal hyperplasia properties. In addition, more neovascularization was observed in BMS compared with DES in the early phase (80% vs. 22%).

In the delayed phase, most BMS and DES showed lipid-laden plaque (77% and 75%, respectively; P = 0.99), while the percentage of lipid-rich plaque tended to be greater in the BMS group than the DES group (41.3 ± 31.2% and 30.0 ± 27.9%, respectively; P = 0.38). In the tissue property analysis, signal attenuation was greater in the BMS group than in the DES group (2.82 ± 1.04% vs. 1.52 ± 1.56%; P = 0.02).

When OCT findings were compared by symptom status (symptomatic n = 35, asymptomatic n = 103), the incidence of lipid-laden plaque was greater in patients with symptomatic restenosis than in those with asymptomatic restenosis (68.6% vs. 37.9%; P < 0.01), as was the percentage of lipid-rich plaque (29.0% vs. 13.5%; P < 0.01). In the tissue property analysis, signal attenuation was significantly greater in the symptomatic group (P < 0.01).

Questions Remain

According to the authors, previous research has suggested that a major mechanism of neoatherosclerosis is the failure to maintain a fully functional endothelialized luminal surface within the stented segment, which might lead to infiltration of macrophages into the neointima. They hypothesize that although this mechanism underlies the changes in both BMS and DES, “the hypersensitivity and inflammatory changes after DES implantation might exaggerate macrophage infiltration and induce an earlier onset of neoatherosclerosis compared to that in BMS, especially in the early and intermediate phases.”

On the other hand, Dr. Jang and colleagues say, the enhanced neovascularization observed in BMS compared with DES during the early phase may have led to more diffuse neoatherosclerosis in the delayed phase. “Additional studies are required to understand the clinical and pathologic significance of the neovascularization observed using OCT,” they write.

Moreover, although previous research has linked neoatherosclerosis with very late stent complications, in the current study lipid-laden plaque and other parameters of unstable neointima were associated with the symptomatic group, the authors note. “These findings suggest that a more vulnerable plaque component may have contributed to the clinical presentation, in addition to the severity of the stenosis,” they conclude.

Study Details

OCT was performed with the M2/M3 Cardiology Imaging System (LightLab Imaging, Westford, MA) and C7-XR OCT Intravascular Imaging System (St. Jude Medical, St. Paul, MN).

Source:

Yonetsu T, Kim J-S, Kato K, et al. Comparison of incidence and time course of neoatherosclerosis between bare metal stents and drug-eluting stents using optical coherence tomography. Am J Cardiol. 2012;Epub ahead of print.

Related Stories:

• Autopsy Study: About One-Third of DES Contain New Atherosclerosis
• DES Associated with Less Downstream Lesion Development than BMS
• CT Plaque Profile Linked to Post-Procedural MI Risk

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