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EXPERIMENTAL STUDY

Pressure rinsing of coronary stents immediately before implantation reduces inflammation and neointimal hyperplasia

^a Division of Cardiovascular Diseases, Mayo Clinic and Foundation, Rochester, Minnesota, USA

Manuscript received December 18, 2000; revised manuscript received April 11, 2001, accepted April 23, 2001.

Reprint requests and correspondence: Dr. Robert S. Schwartz, Division of Cardiovascular Diseases, Mayo Clinic, 200 First Street, SW, Rochester, Minnesota 55905
schwartzr{at}mayo.edu

OBJECTIVES

This study evaluates whether rinsing stents with high pressure immediately before implantation minimizes stent-induced inflammation and neointimal formation.

BACKGROUND

Several reports indicate that manual stent manipulation before implantation results in foreign body contamination and increased neointimal hyperplasia.

METHODS

A stent-cleaning chamber was developed to rinse stents at a sustained hydrodynamic pressure of 4 atm for 10 s. Commercial pre-mounted stents were examined with different levels of manipulation: 1) untouched stents: no stent manipulation before implantation; 2) handled stents: manual stent re-crimping on the balloon; 3) rinsed stents: pressure-rinsed with the stent-cleaning chamber. In vitro surface analysis was evaluated by scanning electron microscopy. Neointimal hyperplasia and inflammation around stent struts were also assessed in the pig in-stent restenosis model.

RESULTS

In vitro analysis revealed fewer contaminants on rinsed stents compared with untouched (p = 0.01) and handled stents (p < 0.001). In vivo, neointimal thickness, neointimal area and vessel percent stenosis were significantly reduced in rinsed, compared with not-rinsed, stents (p = 0.002, p = 0.007, p = 0.008 respectively). In addition, a significant reduction in the inflammatory infiltrate around struts was observed in untouched, compared with handled, stents (p = 0.04) and in rinsed, compared with not-rinsed, stents (p < 0.001). Regression analysis accounting for injury and neointimal thickness showed significant differences in slopes between "handled + not-rinsed" and "handled + rinsed" stents (p = 0.004), and between "untouched + not-rinsed" and "untouched + rinsed stents" (p = 0.037).

CONCLUSIONS

Rinsing stents under high pressure immediately before coronary implantation results in less inflammation around struts and thinner neointima at 28 days in this pig model.

Abbreviations and Acronyms   ANOVA = analysis of variance   IM = intramuscular   MMA = methylmethacrylate

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