One in three thoracic surgery patients with coronary disease had myocardial injury

Design

exploratory post hoc secondary analysis of a randomised controlled trial, Cox models with interaction terms

Population

3,209 patients after non-cardiac thoracic surgery, 331 (10.3%) with coronary artery disease

Primary outcome

myocardial injury after non-cardiac surgery within 14 days

Effect

29.3% vs 18.2%, adjusted HR 1.53 (95% CI 1.22 to 1.92); colchicine interaction by coronary status P = 0.61

A post hoc analysis of the COP-AF trial looked at the 3,209 patients randomised to colchicine 0.5 mg twice daily or placebo for 10 days after non-cardiac thoracic surgery, of whom 331 (10.3%) had known coronary artery disease.

Myocardial injury after non-cardiac surgery occurred in 29.3% of those with coronary disease and 18.2% of those without, adjusted hazard ratio 1.53 (95% CI 1.22 to 1.92, P < 0.001). The composite of death, stroke or myocardial injury followed the same pattern, 30.2% against 18.6%, adjusted HR 1.53 (1.22 to 1.91). Colchicine's effect did not differ by coronary status - hazard ratio for myocardial injury 0.82 (0.55 to 1.22) with coronary disease against 0.91 (0.77 to 1.08) without, interaction P = 0.61.

The number to carry is the denominator, not the hazard ratio. Nearly one in five patients without coronary disease, and nearly one in three with it, sustained detectable myocardial injury after thoracic surgery - mostly silent, mostly found only if troponin is measured. If your unit does not measure postoperative troponin in this population, it is not that these events are rare; it is that they are invisible. The colchicine result is a subgroup question answered with a null: no signal that coronary status should determine who gets it.

• Measure postoperative troponin after thoracic surgery in patients with coronary disease or multiple risk factors
• Expect most myocardial injury to be silent - the diagnosis depends on measuring, not on symptoms
• Do not use coronary status to select patients for perioperative colchicine on this analysis
• Have a written pathway for what a raised postoperative troponin triggers before you start measuring
• Set the risk expectation in consent: roughly one in three with coronary disease in this trial

Why it matters

Perioperative myocardial injury after thoracic surgery is common and silent, so whether it is found at all depends on a local decision to measure troponin.

Don't overread it

Exploratory post hoc subgroup analysis; the absence of a colchicine interaction does not exclude a modest difference between coronary and non-coronary patients.

The statistics, in plain English

An adjusted hazard ratio of 1.53 sounds modest next to the absolute figures, which are the ones that matter here: 29.3% against 18.2%, an 11 percentage point difference. The colchicine subgroup comparison has an interaction P of 0.61, meaning no difference in effect by coronary status was detected - but with only 331 patients in the coronary group, that is a failure to detect rather than a demonstration of equivalence. This is an exploratory post hoc analysis and was not what the trial was designed to answer.

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