Intra-coronary thrombus evolution during acute coronary syndrome: regression assessment by serial optical coherence tomography analyses

Abstract

Aims: Time-domain optical coherence tomography (TD-OCT) allows assessment of the anatomy and features of unstable coronary artery lesions, including discrimination between the thrombotic and atherosclerotic plaque components. We sought to investigate the feasibility of thrombus quantification and its monitoring in patients with high thrombotic burden acute coronary syndromes (ACS). Methods: Patients were suitable for inclusion if they presented with an ACS that was successfully revascularized by manual thrombo-aspiration with a residual large thrombus burden on coronary angiography and initial TD-OCT analysis. These patients underwent a second procedure with TD-OCT analysis after several days of optimal anti-thrombotic therapy and benefited eventually from an intra-coronary stent. Coronary lesion stenosis degree was determined by quantitative coronary angiography (QCA). TD-OCT analysis included measurement of thrombus score (as defined by ESC consensus document), thrombus volume, length and minimal luminal area (MLA), which were quantified by serial area measurement within the athero-thrombotic culprit lesion. Results: Seventeen patients fulfilled inclusion criteria. The OCT image quality was suitable for thrombus quantification in n=14 subjects (86% men/ age=57.9±4.5y/ 93% STEMI). Low molecular weight heparin anticoagulation and dual antiplatelet therapy were given to all patients between the two procedures (mean delay: 3.9.±0.3 days). No adverse events were observed during study time. The values of thrombus score and thrombus volume among individuals highly correlated together rho= 0.8, p<0.0001). We observed a progressive reduction of thrombus burden between the two analyses, as assessed by the significant reductions in thrombus score (22.1±2.6 vs. 10.4±1.4, p=0.001), thrombus volume (9.6±2.4 vs. 4.2±1.2 mm3, p=0.003), length (11.1±1.4 vs. 7.6±0.9 mm, p=0.03) and increase of MLA (2.5±0.4 mm2 vs. 1.7±0.2 mm2, p=0.01). However, the degree of stenosis analyzed by QCA didn't significantly decrease over time. The thrombus burden reduction was time dependent, as the greatest reductions of thrombus score and volume were observed for the longer optimal medical therapy times. The percentages of thrombus score and volume reduction were highly correlated with the inter-OCT analyses delay (respectively r=0.75 and r=0.87, p<0.01 for both). The observed thrombus volume reduction rate was evaluated to 12% of the initial volume per day of optimal medical therapy. Conclusion: TD-OCT assessment of thrombus volume in patients with ACS is feasible, safe and could allow in vivo clot regression monitoring.