Author + information
- Tim A. Fischell, MD, FACC⁎ ()
Reprint requests and correspondence:
Dr. Tim A. Fischell, Director, Cardiovascular Research, Borgess Heart Institute, Professor of Medicine, Michigan State University, 1521 Gull Road, Kalamazoo, Michigan 49048.
In this issue of iJACC (JACC: Cardiovascular Imaging), Hong et al. (1) have made a number of interesting observations regarding the relatively high incidence (27%) and poorer prognosis associated with the intravascular ultrasound finding of tissue prolapse through stent struts in the setting of percutaneous coronary intervention for myocardial infarction (MI). Tissue prolapse through the stent struts was seen more often in patients with ST-segment elevation MI. Prolapse of material through the stent struts was also predicted by positive remodeling, ruptured plaques, and longer stented segments. There was a trend toward a higher frequency of plaque prolapse with open-cell compared to closed-cell stent designs (1).
These main findings fit well with our thinking about the type(s) of plaque material and the results that we might expect when placing a lattice-like metallic structure in plaques that have ruptured and have caused myocardial necrosis (2–5). “Vulnerable plaques” that rupture and cause MI are more typically bulky, lipid-laden, and associated with positive remodeling (3). As these types of plaques rupture, a thrombus may form, break up, and re-form, leaving layers of an organized thrombus that may also behave as “soft” tissue.
One of the potential limitations of the current study is that it may be difficult, using intravascular ultrasound, to distinguish between soft lipid-laden plaque and a “rubbery,” organized thrombus. It is quite possible that an organized thrombus, and not plaque, could represent a significant component of the prolapsed tissue that was observed to protrude through the stent struts.
The finding that plaque prolapse was associated with a greater degree of myocardial necrosis than those cases without tissue prolapse would be consistent with increased distal plaque embolization, greater thrombus formation, transient vessel occlusion, and/or greater thrombus embolization. In any event, it is clear that soft material that protrudes through stent struts is associated with a greater extent of myocardial injury.
Although the study did not identify this tissue prolapse as a statistically significant predictor of subacute stent thrombosis (0 to 30 days), this “negative finding” must be interpreted cautiously. The study was not adequately powered to discern such a difference, and there was a worrisome trend toward greater subacute thromboses in the plaque prolapse group (2.4% vs. 0.9%; p = 0.308).
One of the other interesting findings was the association between stent design and the incidence of plaque or tissue prolapse (1). In this case, the Taxus stent (Boston Scientific Corp., Natick, Massachusetts), which is open-cell and similar in design to the old Tetra stent from Guidant (Santa Clara, California), had plaque prolapse observed in 39% of cases versus 25% of cases with the closed-cell CYPHER stent (Cordis Corp., Miami Lakes, Florida). These findings are consistent with other studies (2,6), including one of our studies comparing the open-cell Duet stent (Guidant) with the closed cell NIR stent (Boston Scientific) (Fig. 1) (6). These observations suggest that better plaque and vessel wall coverage could potentially be advantageous in the setting of stenting for acute MI, with either drug-eluting or bare-metal stents.
The current study by Hong et al. (1) has helped us to elucidate the incidence as well as the clinical and morphological predictors of plaque/tissue prolapse after stenting for acute MI. Although the study was not adequately powered to ascertain with certainty the clinical consequences of plaque prolapse, the study suggests that this finding is unfavorable, with regard to both infarct size, and possibly to the risk of subacute stent thrombosis. Additional longitudinal studies and longer-term follow-up of the cohort from the current study would be useful to help us better understand stent selection and the impact of plaque prolapse after stenting for acute MI.
Dr. Fischell is a consultant for Cordis Corp. and Abbott, and holds license patents with Cordis Corp. and Abbott.
↵⁎ Editorials published in JACC: Cardiovascular Imaging reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Imaging or the American College of Cardiology.
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