Coronary bioresorbable stents: Non-invasive quantitative evaluation of intra- and juxta-stent plaque composition-A computed tomography longitudinal study

Abstract

Purpose: Coronary bioresorbable stents (BRS) do not produce blooming artifacts on computed tomography (CT), in contrast to metallic stents, as they are made of a bioresorbable polymer and are radiolucent. They allow to evaluate the coronary plaque beneath. The low-attenuation plaque (LAP) suggests plaque vulnerability and is CT assessable. The aim of our study was to show the possibility of a non-invasive CT evaluation of the volume and the LAP composition of the intra- and juxta-stent plaque.

Methodology: In our prospective longitudinal study, we recruited 27 consecutive patients (35 BRS stents total; mean age 60 +/- 9 years) with bioresorbable stents for a 256-slice ECG-synchronized CT evaluation at 1- and 12-months post stent implantation. Total plaque volume (mm3), absolute and relative (%) LAP volume per block in the pre- intra- and post-stent zones were analyzed; comparison 1- and 12-months post-implantation of BRS. Changes in the previously mentioned variables were assessed by the mixed effects models with and without spline, which also accounted for the correlation between repeated measurements.

Results: Our block or spline model analysis has shown no significant difference in plaque or absolute LAP volumes in pre- intra- and post-stent zones between 1 and 12 months. Interestingly, % LAP volume increases near-significantly in the distal block of the intrastent at 12-mo follow-up (from 23.38 ± 1.80% to 26.90 ± 2.22% (increase of 15%), p = 0.052).

Conclusion: Our study demonstrates the feasibility of the repeated non-invasive quantitative analysis of the intrastent coronary plaque and of the in-stent lumen by CT scan.

Fig 1. Flow chart of patients bioresorbable coronary stents through the study.

All participants were recruited consecutively from the ReABSORB registry. Six participants were excluded. A total of 27 participants underwent a CT evaluation, then 21 underwent a 12-month follow CT.

Fig 2. Pre-, intra- and post-stent zones composition with 5-mm blocks (vertical rectangles).

Pre-stent zone is the most proximal zone, while post-stent zone is the most distal. Bioresorbable stents also have 2 platinum indicators located at the extremities of the stent in the intrastent blocks numbered 1 and 5. 2016 © ☯Omar Arfa and Evguenia Zdanovich].

Fig 3. Volumetric plaque analysis.

(A) Straightened MPR. There is stenosis at the proximal edge of the BRS in middle left anterior descending coronary artery. (B) Volumetric analysis of plaque HU-stratification. (Ci) Position within the plaque of the axial slice presented in views Cii and Ciii. (Cii) Axial view of lumen in Ci slice. (Ciii) Axial view of the mixed plaque with color-coded LAP and two spotty calcifications. (Di) Position within the plaque of axial slice presented in views Dii and Diii. (Dii) Axial view of lumen in Di slice. (Diii) Axial view of color-coded LAP plaque. (E) Histogram of the plaque composition stratification. LAP (9.19 mm³) represents one third of the total plaque volume (29.8 mm³). 2016 © ☯Omar Arfa and Evguenia Zdanovich].

Fig 4. Intra-stent stenosis.

A). ECG-gated 256-slice coronary CT angiography 14 months after BRS implantation, in a 61-yo woman. An edge and intra-stent mixed plaque with severe stenosis and positive remodeling is shown (arrowhead). Proximal and distal platinum indicators of the BRS (2.5 x 18 mm) are also visible (arrows). 2016 © ☯Carl Chartrand-Lefebvre and Evguenia Zdanovich]. B) Conventional coronary angiography confirms severe intra-stent stenosis. The patient underwent stenting with an everolimus-eluting metallic stent in the same session. 2016 © ☯Samer Mansour].