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Published on: March 27, 2018
High-Sensitivity Cardiac Troponin I and Mortality Following Off-Pump and On-Pump Coronary Artery Bypass Surgery: A
Grace S Lee1, Derrick Y Tam1,2,3, Dominique Vervoort3
1Division of Cardiac Surgery, University of Toronto, Toronto, ON M5G 2C4, Canada.
Insights
High-sensitivity cardiac troponin I (hs-cTnI) thresholds linked to 30-day mortality after coronary artery bypass grafting (CABG) differ between off-pump (OPCAB) and on-pump (ONCAB) procedures. The significant hs-cTnI threshold was lower in OPCAB patients than ONCAB patients.
Area of Science:
- Cardiovascular Surgery
- Cardiac Biomarkers
- Outcomes Research
Background:
- High-sensitivity cardiac troponin I (hs-cTnI) is a critical biomarker for assessing myocardial injury post-cardiac surgery.
- Coronary artery bypass grafting (CABG), both on-pump (ONCAB) and off-pump (OPCAB), carries risks of myocardial damage indicated by hs-cTnI levels.
- Understanding hs-cTnI thresholds associated with mortality is crucial for risk stratification after CABG.
Purpose of the Study:
- To investigate if hs-cTnI thresholds predicting 30-day mortality after isolated CABG differ between OPCAB and ONCAB procedures.
- To identify specific hs-cTnI levels associated with increased mortality risk in each surgical group.
Main Methods:
- Subanalysis of the VISION Cardiac Surgery Study involving 6,505 patients undergoing isolated CABG.
- Cox regression analysis to determine hazard ratios (HRs) for 30-day mortality based on postoperative day one log-transformed hs-cTnI.
- Interaction term (OPCAB vs. ONCAB) used to assess differential effects of hs-cTnI on mortality, identifying thresholds where HR ≥ 1.00.
Main Results:
- Median hs-cTnI was significantly lower in OPCAB (640 ng/L) compared to ONCAB (2,972 ng/L) (p < 0.001).
- No significant difference in 30-day mortality between OPCAB (1.7%) and ONCAB (1.4%) (p = 0.5).
- A significant interaction effect (p = 0.002) showed a lower hs-cTnI threshold for increased mortality in OPCAB (≥4,708 ng/L) versus ONCAB (≥6,806 ng/L).
Conclusions:
- The hs-cTnI threshold associated with increased 30-day mortality risk post-CABG is higher than current guideline thresholds.
- This clinically significant hs-cTnI threshold is lower for patients undergoing OPCAB compared to ONCAB.
- Findings suggest differential interpretation of hs-cTnI levels based on CABG surgical strategy is warranted.
Objectives:
We aimed to determine whether high-sensitivity cardiac troponin I (hs-cTnI) thresholds associated with increased 30-day mortality isolated coronary artery bypass grafting (CABG) differed between those undergoing off-pump (OPCAB) and on-pump (ONCAB) CABG.
Methods:
We conducted a subanalysis of patients who underwent isolated CABG in the Vascular Events in Surgery Patients Cohort Evaluation (VISION) Cardiac Surgery Study. Cox regression was used to determine the hazard ratios (HRs) for mortality based on postoperative day 1 log-transformed hs-cTnI adjusted by EuroSCORE II, with OPCAB versus ONCAB as an interaction term. HRs were modelled as a function of hs-cTnI, and the lowest troponin associated with HR ≥ 1.00 was identified for each group.
Results:
Of the original VISION cohort, 6505 patients underwent isolated CABG (OPCAB = 1141, ONCAB = 5364). Median hs-cTnI after CABG was 2446 ng/L (interquartile range [IQR] 1164-5654), and lower after OPCAB (640 ng/L [264-1689]) than ONCAB (2972 ng/L [1536-6448], P < .001). There were no differences in 30-day mortality between OPCAB and ONCAB (1.7% vs 1.4%, P = .5). Increased log-peak hs-cTnI was associated with greater mortality after CABG (adjusted HR = 1.7 [95% CI, 1.4-2.1]). The hs-cTnI threshold associated with HR ≥ 1.00 for isolated CABG was 6549 ng/L (95% CI, 3609-8381). OPCAB versus ONCAB had a significant interaction effect on the association between hs-cTnI and mortality (interaction P = .002). The hs-cTnI threshold associated with mortality after OPCAB was ≥4708 ng/L (95% CI, 581-7177), compared to ≥6806 ng/L (95% CI, 4001-13 993) after ONCAB.
Conclusions:
The clinically significant hs-cTnI threshold after CABG associated with an increased risk of 30-day mortality above the baseline is substantially higher than defined by current guidelines, but lower in patients undergoing OPCAB compared to ONCAB.
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