Optical coherence tomography assessment of the impact of colchicine on non-culprit coronary plaque composition after myocardial infarction

Low-dose colchicine reduces the risk of cardiovascular events after myocardial infarction (MI). The purpose of this study was to assess the effect of colchicine post-MI on coronary plaque morphology in non-culprit segments by optical coherence tomography (OCT).

COCOMO-ACS was a double-blind, placebo-controlled trial that randomized 64 patients (median age 61.5 years; 9.4% female) with acute non-ST-segment elevation MI to colchicine 0.5 mg daily or placebo for a median of 17.8 months in addition to guideline-recommended therapy. Participants underwent serial OCT imaging within a matched segment of non-culprit coronary artery that contained at least one lipid-rich plaque causing ≥20% stenosis. The primary outcome was the change in minimum fibrous cap thickness (FCT) in non-culprit segments from baseline to final visit. Of those randomized, 57 (29 placebo, 28 colchicine) had evaluable imaging at baseline and follow-up. Overall, colchicine had no effect on relative (placebo +48.0 ± 35.1% vs. colchicine +62.4 ± 38.1%, P = 0.18) or absolute changes in minimum FCT (+29.2 ± 20.9 µm vs. + 37.2 ± 21.3 µm, P = 0.18), or change in maximum lipid arc (−38.8 ± 32.2° vs. −54.8 ± 46.9°, P = 0.18) throughout the imaged non-culprit segment. However, in patients assigned colchicine, cap rupture was less frequent (placebo 27.6% vs. colchicine 3.6%, P = 0.03). In post hoc analysis of 43 participants who had been followed for at least 16 months, minimum FCT increased to a greater extent in the colchicine group (placebo +38.7 ± 25.4% vs. colchicine +64.7 ± 34.1%, P = 0.005).

In this study, OCT failed to detect an effect of colchicine on the minimum FCT or maximum lipid arc of plaques in non-culprit segments post-MI. The post hoc observation that minimum FCT increased to a greater extent with colchicine after more prolonged treatment suggests that longer-term studies may be required to detect the effect of anti-inflammatory therapies on plaque morphology by OCT.

Australian New Zealand Clinical Trials Registry Identifier, ACTRN12618000809235, registered on the 11 May 2018.