Abstract 14145: Relationship of Pharmacokinetic and Biomechanical Parameters With Intraplaque Haemorrhage- An in vivo Carotid MR Imaging Study

Introduction: Atheromatous neovessels with high permeability have been implicated in the evolution of intraplaque haemorrhage (IPH). In vivo quantification of vasa vasorum permeability is possible using dynamic-contrast enhanced-magnetic resonance (DCE-MR) imaging. Hypothesis: In vivo relationship of extent of leakiness of neovessels with critical biomechanical forces i.e. stress and strain in atheroma and with IPH remains unreported. Methods: Patients with mild to severe carotid artery stenosis underwent DCE-MR imaging of their bilateral carotid arteries on a 3 Tesla MR system, using TRICKS method. A two-compartment Patlak model was used to generate a parametric map showing partial plasma volume (vp) and K trans. FEA simulations were performed for stress and strain analyses. For histological analysis, carotid plaques were processed and stained. Results: Sixteen patients underwent carotid MR imaging. The two groups were comparable for their demographics and co-morbidities. Peak structural stress (PSS) and peak strain (P1) were significantly higher in symptomatic versus asymptomatic patients (p=0.002 and 0.009 respectively). Carotid atheroma with IPH had higher PSS and P I compared to those without IPH [p=0.036 and 0.009]. Variations in stress during one cardiac cycle was significantly greater among plaques with IPH (p=0.01); variation in strain was greater in atheroma with IPH [p=0.04]. Adventitial K trans was higher in carotid atheroma of symptomatic patients than asymptomatic cohort (p= 0.016). Plaque K trans , adventitial and plaque v p were however comparable for both patient cohorts (p= 0.81, 0.96, 0.36 respectively). Adventitial K trans and plaque v p were higher in atheroma with IPH (p= 0.04, 0.01) but comparable for plaque K trans and adventitial v p (p=0.46, 0.88 respectively). A strong correlation was observed between variations in strain during the cardiac cycle with adventitial K trans for plaques with IPH [Pearson r : 0.84, p=0.03]. Conclusions: A strong correlation exists between adventitial neovessel permeability and variations in strain in atheroma with IPH. Carotid atheroma with IPH have higher biomechanical stresses and strain and variations in these critical biomechanical conditions compared to non-IPH atheroma.