CLINICAL RESEARCH Interventional Cardiology Slow-Flow Phenomenon During Carotid Artery Intervention With Embolic Protection Devices Predictors and Clinical Outcome

OBJECTIVES The purpose of this research was to define the predictors of the “slow-reflow” phenomenonduring carotid artery intervention with filter-type embolic protection devices (EPDs) and todetermine its prognostic significance.BACKGROUND During carotid artery intervention using filter-type EPDs, we have observed cases in whichthere is angiographic evidence of a significant reduction in antegrade flow in the internalcarotid artery proximal to the filter device, termed “slow-flow.” The predictors of thisphenomenon and its prognostic significance are unknown.METHODS Using a single-center prospective carotid intervention registry, patients with slow-flow werecompared to patients with normal flow during carotid intervention with respect to clinical,procedural, and lesion characteristics, and the 30-day incidence of death and stroke.RESULTS A total of 414 patients underwent 453 carotid artery interventions using EPDs. Slow-flowoccurred in 42 patients (10.1%) undergoing 42 carotid interventions (9.3%), and mostcommonly occurred after post-stent balloon dilatation (71.4%). Multivariate logistic regres-sion analysis identified the following predictors of slow-flow: recent history ( 6 months) ofstroke or transient ischemic attack (odds ratio [OR] 2.8, 95% confidence interval [CI] 1.4 to5.6, p 0.004), increased stent diameter (OR 1.4, 95% CI 1.02 to 1.94, p 0.044), andincreased patient age (OR 1.05, 95% CI 1.01 to 1.09, p 0.025). Among patients withslow-flow, the 30-day incidence of stroke or death was 9.5% compared to 2.9% in patientswith normal flow (chi-square 4.73, p 0.03). This difference was driven by the disparityin the 30-day incidence of stroke (9.5% vs. 1.7%).CONCLUSIONS Slow-flow during carotid intervention with EPDs is a frequent event that is associated withan excess risk of periprocedural stroke. The association of the phenomenon with clinicallysymptomatic carotid lesions and use of larger stent diameters suggests that embolization ofvulnerable plaque elements may play a pathogenic role. (J Am Coll Cardiol 2005;46:1466–72) © 2005 by the American College of Cardiology Foundation