Anti-inflammatory agent favorably modifies vulnerable coronary plaque
Colchicine Therapy and Plaque Stabilization in Patients With Acute Coronary Syndrome: A CT Coronary Angiography Study
Inflammation contributes to plaque development, and may promote plaque instability and acute coronary syndrome (ACS). Inflammation is not restricted to the culprit stenosis in the coronary vasculature; persistent inflammatory cell activation at sites remote from an index plaque rupture may lead to recurrent events.
Colchicine is an inexpensive, anti-inflammatory medication that may have a beneficial role in the prevention of CV disease. Short-term colchicine administration in patients with ACS has recently been shown to significantly reduce systemic and local transcoronary production of inflammatory cytokines implicated in atherosclerosis . It is unknown whether these cytokine changes have favorable influence on plaque.
Coronary computed tomography angiography (coronary CTA) can detect significant coronary artery anatomic stenoses, and also allows detailed examination of coronary plaque composition noninvasively. Plaque morphology features such as low attenuation plaque (LAP), positive remodeling, spotty calcification and the ‘napkin ring’ sign, are suggestive of vulnerability to rupture and associate with future ACS. LAP has been shown to be the strongest prognostic predictor of adverse CV events [2,3].
This is a prospectively designed (open-label, single center) pilot study to investigate if colchicine therapy (0.5 mg/day) affects certain adverse plaque characteristics, as assessed by coronary CTA. The effect of 12 months colchicine therapy was evaluated, in patients who had presented with ACS in the preceding month (mean follow-up 12.6±2.8 months). Both the colchicine group (n=40) and the control arm (n=40) underwent statin and risk factor optimization. Change in LAP volume (LAPV) was the primary endpoint.
- Significant reductions in all coronary CTA measures were seen: total atheroma volume (TAV), noncalcified plaque volume (NCPV), dense calcified plaque volume (DCPV) and remodeling index, both in the colchicine and control arms.
- Colchicine therapy was associated with a significantly lower LAPV than was seen in the control group (mean -15.9 (-40.9%) ±17.3 mm³ vs. -6.6 (-17%) ±12.8 mm³, P=0.008).
- High-sensitivity C-reactive protein (hsCRP) was also significantly lower in the colchicine arm at the end of follow-up (mean: 1.10 (-37.3%) ±1.15 mg/L vs. 0:38 (-14.6%) ±1.21 mg/L, P<0.001).
- TAV was nonsignificantly reduced at follow up in the treatment vs control group, and no significant differences were seen for DCPV, NCPV or remodeling index. Nor did changes in TAV, DCPV and NCPV as a proportion of TVV differ significantly between groups.
- LDL-c reductions were appropriate and comparable between groups (mean 0.44 (-19.0%) ± 0.60 mmol/L vs 0.49 (-20.2%) ±0.49 mmol/L, P-0.21).
- In multivariate linear regression analysis, colchicine therapy remained significantly associated with reduction in LAPV and hsCRP, as compared with controls. No significant differences between groups were seen in the other outcomes.
- In a correlation analysis between the 2 significant outcome variables, a significant linear relationship was found (R²=0.158, P<0.001) and a positive correlation (r=0.578) between change in LAPV and change in hsCRP. Change in LAPV showed a significant linear relationship (R²=0.123, P=0.001) and moderate correlation (r=0.417) with change in LDL, while hsCRP did not (R²=0.047, P=0.06).
- One person experienced gastrointestinal intolerance as an adverse event from colchicine and treatment was stopped. Treatment was stopped in two other cases for unknown reasons, and two patients were non-compliant. No MI or death occurred in either group during follow-up.
This study shows that low-dose colchicine treatment has greater coronary plaque-stabilizing effects than optimal medical therapy, as is evident from a reduction of LAPV and hsCRP. The modest positive correlation between change in LDL and change in LAP volume suggests that LDL reduction may have contributed to plaque stabilization, but the similar LDL reduction in both groups indicates that the changes in plaque morphology are not solely driven by changes in LDL. The larger reduction in hsCRP in the colchicine group suggests that its anti-inflammatory properties play a role.
Over the past twenty years, various lines of evidence have demonstrated the link between CRP and inflammation and future CV risk. Studies had also suggested that lowering hsCRP, just like LDL-c, is beneficial, but the proof that inflammation is causal in atherosclerosis came from the recent randomized CANTOS trial in which inflammation was lowered in the absence of lipid lowering. Indeed, treatment with the interleukin-1β antibody canakinumab reduced the primary endpoint of MI, stroke or CV death without changing LDL-c. Another large-scale randomized trial, CIRT, evaluating low-dose methotrexate is still underway. Colchicine has shown promise for secondary prevention in preliminary trials.
Various surrogate imaging markers for atherosclerosis and vascular inflammation have been examined. Ridker and Narula  call the finding of reduced LAP volume provocative, because LAP is considered an imaging marker for instability and a predictor of adverse CV events. They note ‘Vaidya et al report little if any effect of colchicine on total atheroma volume, a finding suggesting plaque modification and stabilization.’
They point out several limitations of the current study, including the lack of randomization, thus it being subject to confounding and bias. Moreover, control patients were derived from a general cardiology clinic, thus they were likely to differ from the ACS patients in the intervention group. Ridker and Narula are critical of surrogate imaging markers: ‘Although imaging-verified change in plaque composition (including LAP or inflammation) should be intuitively more informative than the interval change in the percentage of atheroma volume in response to therapeutic intervention, it is likely that no imaging modality would succeed as a validated surrogate for hard clinical events.’ They name various examples, including a recent MRI study of the carotid arteries and aorta that did not demonstrate significant effects of canakinumab on measures of vascular structure and function, despite evidence of hsCRP lowering.
Still, they conclude that imaging can likely serve as a useful tool to understand the pathogenesis of atherosclerosis and the effects of drugs on these mechanisms. The authors anticipate that, after presentation of the CANTOS results, the search for valid imaging surrogate predictive of drug effects will likely accelerate.