Stratification of risk in thin cap fibroatheromas using peak plaque stress estimates from idealized finite element models

Thin cap fibroatheroma (TCFA) in coronary arteries is believed to be associated with plaque rupture leading to cardiovascular death and non-fatal myocardial infarction. Catheter-based imaging platforms can identify TCFAs but detection algorithms lack specificity. Here we report results of an exploratory study of the variability in TCFA plaque attributes and effects on peak von Mises stress of TCFA using idealized finite element models. A total of 1272 idealized TCFA finite element models were developed by strategically varying attribute dimensions - external elastic membrane diameter, lumen diameter, necrotic core thickness, fibrous cap thickness, and necrotic core angle - obtained from a global registry of subjects undergoing percutaneous coronary intervention with Virtual Histology intravascular ultrasound. Peak stress exhibited parabolic or higher order proportionality with lumen diameter, sigmoidal proportionality with necrotic core thickness, inverse hyperbolic proportionality with fibrous cap thickness, and skewed sinusoidal proportionality with necrotic core angle. Each of these relationships was governed by highly sensitive, complex, and interdependent influences of various attributes on plaque stress. An over 7-fold increase in peak stress from 101 to 788kPa was observed in models of coronary dimensions commonly encountered in clinical practice. Peak stress of intramural TCFA within this common coronary artery subset did not exceed 300kPa for fibrous cap thickness greater than 100μm and necrotic core angle outside 90-120° range, indicating low risk of rupture. This exploratory study demonstrated the complex and interdependent influence of plaque attributes on the peak stress of TCFA.