Coronary Plaque Structural Stress Is Associated With Plaque Composition and Subtype and Higher in Acute Coronary Syndrome: The BEACON I (Biomechanical Evaluation of Atheromatous COroNary Arteries) Study
Background—Atherosclerotic plaques underlying most myocardial infarctions have thin fibrous caps and large necrotic cores; however these features alone do not reliably identify plaques that rupture. Rupture occurs when plaque structural stress (PSS) exceeds mechanical strength. We examined whether PSS could be calculated in vivo based on virtual histology intravascular ultrasound (VH-IVUS), and whether PSS varied according to plaque composition, subtype or clinical presentation.
Methods and Results—4,429 VH-IVUS frames from 53 patients were analyzed, identifying 99,584 individual plaque components. PSS was calculated by finite element analysis (FEA) in whole vessels, in individual plaques and in higher-risk regions (plaque burden (PB)≥70%, mean luminal area (MLA)≤4mm2, non-calcified VH-defined thin-cap fibroatheroma (ncVHTCFA)). Plaque components including total area/arc of calcification (R2=0.33, p<0.001 and R2=0.28, p<0.001) and necrotic core (R2=0.18, p<0.001 and R2=0.15, p<0.001) showed complex, non-linear relationships with PSS. PSS was higher in ncVHTCFA compared with thick-cap fibroatheromas (8.44 [6.97-10.64] vs. 7.63 [6.37-9.68](median [Q1-Q3], p=0.002). PSS was also higher in patients with an acute coronary syndrome (ACS) where MLA≤4mm2 (8.24 [7.06-9.93] vs. 7.72 [6.33-9.34], p=0.03), PB≥70% (9.18 [7.44-10.88] vs. 7.93 [6.16-9.46], p=0.02), and in ncVHTCFA (9.23 [7.33-11.44] vs. 7.65 [6.45-8.62], p=0.02). Finally, PSS increased the positive predictive value for VH-IVUS to identify clinical presentation.
Conclusions—FEA modeling demonstrates that structural stress is highly variable within plaques, with increased PSS associated with plaque composition, subtype, and higher-risk regions in ACS patients. PSS may represent a novel tool to analyze the dynamic behavior of coronary plaques with the potential to improve prediction of plaque rupture.
- Received December 8, 2013.
- Accepted February 18, 2014.