Mechanism of Lumen Enlargement During Intracoronary Stent Implantation

Background —Intravascular ultrasound analysis has assessed mechanisms of lumen enlargement after nonstent interventions, but not after stenting. Methods and Results —Preintervention and postintervention intravascular ultrasound was used to study 25 de novo native coronary lesions treated with single MultiLink stents without preatheroablation. External elastic membrane, lumen, and plaque and media (P&M) areas were measured every 1 mm to include the lesion and reference segments that were 5 mm proximal and distal to it. Lesion mean lumen area increased from 4.0±1.0 mm 2 before the intervention to 8.8±2.0 mm 2 after the intervention ( P <0.0001) as a result of an increase in mean external elastic membrane area (14.2±2.7 to 16.1±3.0 mm 2 , P <0.0001) and a decrease in mean P&M area (10.2±2.2 to 7.2±1.8 mm 2 , P <0.0001). The decrease in lesion P&M was accompanied by an increase in both proximal reference mean P&M (7.0±1.9 to 8.4±2.0 mm 2 , P <0.0001) and distal reference mean P&M (5.8±2.1 to 7.2±2.1 mm 2 , P <0.0001). Volumetric analysis showed an axial redistribution of plaque away from the center of the lesion toward the reference segments to increase the plaque burden in both the proximal and distal reference segments. Total (lesion plus reference) mean P&M decreased from 8.6±2.1 to 7.5±1.8 mm 2 ( P <0.0001). Conclusions —The mechanisms of lumen enlargement after stenting involved (1) significant axial redistribution of plaque from the lesion into the reference segments, (2) vessel expansion, and (3) either plaque embolization or compression.