The Role Mechanical Forces Play in Advanced Human Carotid Plaque Progression: New Insights from an In Vivo MRI Multi-Year Patient-Tracking 3D FSI Study

Abstract

Although many studies have been conducted for atherosclerosis initiation and progression at the molecular, cellular, and organ levels using in vitro experimental and animal models, patient-specific atherosclerosis plaque progression studies are relatively rare in the literature. In this progression study, fourteen patients were scanned 2-4 times at 18-month intervals using a histologically validated multi-contrast magnetic resonance imaging (MRI) protocol to acquire carotid plaque progression data. Thirty-two scan pairs (baseline and follow-up) were formed for analysis. The averaged plaque stenosis severity by area was 75%. Twenty-three pairs showed plaque progression, as indicated by positive mean vessel wall thickness increase (WTI), while 9 pairs showed plaque regression with negative mean WTI. 3D fluid-structure interaction (FSI) models were constructed and plaque wall stress (PWS) and flow shear stress (FSS) were obtained from all matching lumen data points (400-1000 per plaque; 100 points per slice). For the progression group, using FSS and PWS data at follow-up scan, 17 out of 23 pairs showed a significant positive correlation between FSS and WTI; 19 out of 23 pairs showed a significant negative correlation between PWS and WTI. At baseline, the (positive : negative : no significance) correlation ratio between FSS and WTI was (8:10:5). The correlation ratio between PWS and WTI was (13:5:5). Correlation results for the regression group were weaker than the progression group. The results indicate that correlations between mechanical stresses (FSS and PWS) and plaque progression for advanced carotid plaques may be different from those observed in plaque initiation and early-stage progression.KeywordsPlaque progressionblood flowatherosclerosisplaque rupturefluid-structure interaction