Carotid plaque regression following 6-month statin therapy assessed by 3T cardiovascular magnetic resonance: comparison with ultrasound intima media thickness

<p>Abstract</p> <p>Background</p> <p>Cardiovascular magnetic resonance (CMR) allows volumetric carotid plaque measurement that has advantage over 2-dimensional ultrasound (US) intima-media thickness (IMT) in evaluating treatment response. We tested the hypothesis that 6-month statin treatment in patients with carotid plaque will lead to plaque regression when measured by 3 Tesla CMR but not by IMT.</p> <p>Methods</p> <p>Twenty-six subjects (67 ± 2 years, 7 females) with known carotid plaque (> 1.1 mm) and coronary or cerebrovascular atherosclerotic disease underwent 3T CMR (T1, T2, proton density and time of flight sequences) and US at baseline and following 6 months of statin therapy (6 had initiation, 7 had increase and 13 had maintenance of statin dosing). CMR plaque volume (PV) was measured in the region 12 mm below and up to 12 mm above carotid flow divider using software. Mean posterior IMT in the same region was measured. Baseline and 6-month CMR PV and US IMT were compared. Change in lipid rich/necrotic core (LR/NC) and calcification plaque components from CMR were related to change in PV.</p> <p>Results</p> <p>Low-density lipoprotein cholesterol decreased (86 ± 6 to 74 ± 4 mg/dL, p = 0.046). CMR PV decreased 5.8 ± 2% (1036 ± 59 to 976 ± 65 mm³, p = 0.018). Mean IMT was unchanged (1.12 ± 0.06 vs. 1.14 ± 0.06 mm, p = NS). Patients with initiation or increase of statins had -8.8 ± 2.8% PV change (p = 0.001) while patients with maintenance of statin dosing had -2.7 ± 3% change in PV (p = NS). There was circumferential heterogeneity in CMR plaque thickness with greatest thickness in the posterior carotid artery, in the region opposite the flow divider. Similarly there was circumferential regional difference in <it>change </it>of plaque thickness with significant plaque regression in the anterior carotid region in region of the flow divider. Change in LR/NC (R = 0.62, p = 0.006) and calcification (R = 0.45, p = 0.03) correlated with PV change.</p> <p>Conclusions</p> <p>Six month statin therapy in patients with carotid plaque led to reduced plaque volume by 3T CMR, but ultrasound posterior IMT did not show any change. The heterogeneous spatial distribution of plaque and regional differences in magnitude of plaque regression may explain the difference in findings and support volumetric measurement of plaque. 3T CMR has potential advantage over ultrasound IMT to assess treatment response in individuals and may allow reduced sample size, duration and cost of clinical trials of plaque regression.</p

Contribution of Mechanical and Fluid Stresses to the Magnitude of In-stent Restenosis at the Level of Individual Stent Struts

Structural and fluid stresses acting on the artery wall are proposed as mechanical mediators of in-stent restenosis (ISR). This study reports an investigation of the correlation between stresses obtained from computational simulations with the magnitude of ISR at the level of individual stent struts observed in an in vivo model of restenosis. Structural and fluid dynamic analyses were undertaken in a model based on volumetric micro-CT data from an in vivo stent deployment in a porcine right coronary artery. Structural and fluid mechanics were compared with histological data from the same stented vessel sample. Interpretation of the combined data at the level of individual stent struts was possible by identifying the location of each 2-D histological section within the 3-D micro-CT volume. Linear correlation between structural and fluid stimuli and neointimal thickness at the level of individual struts is less clear when individual stimuli are considered [compressive force (CF), R 2 = 0.19, wall shear stress (WSS), R 2 = 0.25, oscillatory shear index (OSI), R 2 = 0.28]. Closer correlation is observed if combined structural and fluid stimuli are assumed to stimulate ISR (CF/WSS, R 2 = 0.64). The use of micro-CT to characterise stent geometry after deployment enhances the clinical relevance of computational simulations, allowing direct comparison with histology. The results support the combined role of both structural and fluid mechanics to determine the magnitude of ISR at the level of individual struts. This finding is consistent with other studies which consider these stimuli averaged over a transverse section of the vessel

Patient-specific computer modelling of coronary bifurcation stenting: the John Doe programme

John Doe, an 81-year-old patient with a significant distal left main (LM) stenosis, was treated using a provisional stenting approach. As part of an European Bifurcation Club (EBC) project, the complete stenting procedure was repeated using computational modelling. First, a tailored three-dimensional (3D) reconstruction of the bifurcation anatomy was created by fusion of multislice computed tomography (CT) imaging and intravascular ultrasound. Second, finite element analysis was employed to deploy and post-dilate the stent virtually within the generated patient-specific anatomical bifurcation model. Finally, blood flow was modelled using computational fluid dynamics. This proof-of-concept study demonstrated the feasibility of such patient-specific simulations for bifurcation stenting and has provided unique insights into the bifurcation anatomy, the technical aspects of LM bifurcation stenting, and the positive impact of adequate post-dilatation on blood flow patterns. Potential clinical applications such as virtual trials and preoperative planning seem feasible but require a thorough clinical validation of the predictive power of these computer simulations