Debra L. Beck, MSc, and Eugene Braunwald, MD

High-sensitivity troponin I is the preferred biomarker for detecting perioperative myocardial infarction and clinically-important periprocedural myocardial injury after cardiac surgery, but consensus recommendations regarding the threshold levels range widely (from >10 times to ≥70 times the upper reference limit for the assay).

Devereaux and the VISION Cardiac Surgery Investigators conducted an international prospective cohort study to determine the relationship between postoperative high-sensitivity cardiac troponin I (hs-TnI) levels and the risk of death within 30 days of cardiac surgery. Hs-TnI measurements (upper reference limit, 26 ng per liter) were obtained 3 to 12 hours after cardiac surgery and on days 1, 2, and 3 after surgery. Of 13,862 patients included for analysis (mean age, 63 years, 71% male), 296 (2.1%) died within 30 days of surgery.

Among those who underwent isolated coronary-artery bypass grafting or aortic-valve replacement or repair, the threshold troponin level, measured within 1 day after surgery, that was associated with an adjusted hazard ratio of more than 1.00 for death within 30 days was 5670 ng per liter (95% confidence interval [CI], 1045 to 8260), a level 218 times the upper reference limit. For those patients who underwent other cardiac surgeries, the corresponding threshold troponin level was 12,981 ng per liter (95% CI, 2673 to 16,591), a level 499 times the upper reference limit.

Summary

The investigators concluded that the lowest levels of hs-TnI after cardiac surgery that were associated with an increased risk of death at 30 days were substantially higher than levels currently recommended to define clinically-important periprocedural myocardial injury.

The recommended troponin thresholds suggested by consensus statements (>10, ≥35, and ≥70 times the upper reference limit), were exceeded in 97.5%, 89.4%, and 74.7% of patients, respectively, within the first day after surgery, noted the authors. These results are specific to hs-TnI and cannot be generalized to other cardiac troponin assays.

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