Article Identification

  • Article Title: Undetectable High-Sensitivity Cardiac Troponin T Level in the Emergency Department and Risk of Myocardial Infarction
  • Citation: Bandstein, N., Ljung, R., Johansson, M., & Holzmann, M.J. (2014). Undetectable High-Sensitivity Cardiac Troponin T Level in the Emergency Department and Risk of Myocardial Infarction. Journal of the American College of Cardiology, 63(23), 2569–2578. https://doi.org/10.1016/j.jacc.2014.03.017
  • DOI: 10.1016/j.jacc.2014.03.017
  • PMID: 24694529

Quick Reference Summary

  • Patients presenting with chest pain who have an initial hs-cTnT level of <5 ng/l and an ECG without signs of ischemia exhibit a 99.8% negative predictive value for myocardial infarction (MI) within 30 days, enabling safe discharge from the emergency department (ED).
  • The study reported an absolute risk of MI of 0.17% and 100% negative predictive value for death within 30 days for this low-risk group, emphasizing the clinical safety of early ED discharge.

Core Clinical Question

Can an initial undetectable high-sensitivity cardiac troponin T (hs-cTnT) level (<5 ng/l) combined with an ECG without signs of ischemia safely rule out myocardial infarction in patients presenting to the emergency department with chest pain?

Background

  • Chest pain is a common ED presentation, with 15-20 million visits annually in Europe and the USA.
  • Myocardial Infarction (MI) is a critical condition often necessitating prompt diagnosis to prevent mortality and morbidity.
  • Current standard of care involves serial troponin measurements and prolonged observation, leading to high hospitalization rates (80-90%) with only 10-20% diagnosed with MI.
  • High-sensitivity cardiac troponin T (hs-cTnT) assays offer earlier detection of myocardial injury, potentially reducing the need for serial testing and hospital admissions.
  • Knowledge gaps:
    • Effectiveness of single hs-cTnT measurements combined with ECG in ruling out MI.
    • Safety and feasibility of early ED discharge based on initial hs-cTnT and ECG findings.
  • Study rationale: To evaluate if a single undetectable hs-cTnT and non-ischemic ECG can safely exclude MI, thereby streamlining ED processes.

Methods Summary

  • Study Design: Retrospective cohort study
  • Setting and Time Period: Karolinska University Hospital, Stockholm, Sweden; December 10, 2010 – December 31, 2012
  • Population Characteristics: 14,636 patients presenting with chest pain; Age >25 years
  • Inclusion/Exclusion Criteria:
    • Included: Patients with chest pain and at least one hs-cTnT measurement
    • Excluded: Patients with ECG signs of MI despite hs-cTnT <5 ng/l
  • Intervention Details:
    • First hs-cTnT level categorized as <5, 5-14, >14 ng/l
    • ECG Assessment for ischemic changes
  • Control/Comparison Groups: Based on hs-cTnT levels: <5 ng/l, 5-14 ng/l, >14 ng/l
  • Primary and Secondary Outcomes:
    • Primary: MI within 30 days
    • Secondary: MI at 180 and 365 days, all-cause mortality at 30, 180, 365 days
  • Statistical Analysis Approach: Negative predictive values, absolute risks, Cox proportional hazards models
  • Sample Size Calculations: 14,636 patients included
  • Ethics and Funding Information: Approved by Regional Ethical Review Board in Stockholm; No reported conflicts of interest

Detailed Results

  • Participant Flow and Demographics:
    • 61% (8,907) had hs-cTnT <5 ng/l
    • 21% (3,150) had 5-14 ng/l
    • 18% (2,579) had >14 ng/l
    • Lower hs-cTnT group: Younger, fewer comorbidities
  • Primary Outcome Results:
    • Undetectable hs-cTnT & non-ischemic ECG: 39 MI events (0.44%)
    • Negative Predictive Value: 99.8% (95% CI: 99.7–99.9)
    • Absolute Risk of MI: 0.17% (95% CI: 0.09–0.27)
  • Effect Sizes and Confidence Intervals:
    • Death within 30 days: 100% NPV (95% CI: 99.9–100)
  • Secondary Outcome Results:
    • MI at 180 days: 0.37% risk, 99.6% NPV
    • MI at 365 days: 0.61% risk, 99.4% NPV
    • Death within 365 days: 0.43% risk, 99.6% NPV
  • Subgroup Analyses:
    • Older, male patients with comorbidities had higher MI risk despite undetectable hs-cTnT
  • Adverse Events/Safety Data:
    • No deaths in the undetectable hs-cTnT group within 30 days

Results Tables

Outcome Intervention Group (<5 ng/l) Control Group (5-14 ng/l) High-risk Group (>14 ng/l) Difference (95% CI) P-value
MI within 30 days 0.17% (0.09–0.27) 3.08% (2.48–3.68) 26.2% (24.5–27.9) P < 0.001 N/A
Death within 30 days 0.023% (0.001–0.054) 0.41% (0.19–0.64) 2.56% (1.95–3.17) P < 0.001 N/A
MI within 180 days 0.37% (0.24–0.54) 3.65% (2.99–4.30) 28.1% (26.3–29.8) P < 0.001 N/A
Death within 365 days 0.43% (0.29–0.78) 3.43% (2.79–4.06) 13.3% (12.0–14.6) P < 0.001 N/A

Authors' Conclusions

  • Primary Conclusions:
    • Undetectable hs-cTnT (<5 ng/l) with a non-ischemic ECG effectively rules out MI and death within 30 days, supporting safe ED discharge.
  • Authors' Interpretation:
    • This single measurement strategy can significantly reduce hospital admissions, addressing ED overcrowding and healthcare costs.
  • Clinical Implications:
    • Implementation of this strategy could streamline chest pain protocols, ensuring efficient use of resources while maintaining patient safety.
  • Future Research Recommendations:
    • Prospective studies to validate findings
    • Integration with other clinical decision tools

Critical Analysis

A. Strengths

  • Large Sample Size: Included 14,636 patients, enhancing statistical power.
  • Real-World Setting: Conducted in a busy ED, ensuring generalizability.
  • Comprehensive Data: Utilized national registers for complete follow-up.
  • High Negative Predictive Value: Demonstrated 99.8% NPV for MI exclusion.
  • Minimal Bias: No relevant conflicts of interest, enhancing study credibility.

B. Limitations

  • Retrospective Design: Subject to selection bias and confounding factors.
  • Single-Center Study: May limit external validity to other settings or populations.
  • Lack of Serial Troponin Measurements: Potentially missed dynamic changes indicative of MI.
  • Excluded Patients with Ischemic ECG Changes: May underestimate MI prevalence in the undetectable hs-cTnT group.
  • No Assessment of Pretest Probability: Limits understanding of clinical context in MI exclusion.
  • Limited Long-Term Data: While 365-day outcomes were assessed, longer follow-up might provide more insights.

Clinical Application

  • Changing Current Practice: Implementing single hs-cTnT and ECG assessment can safely discharge low-risk chest pain patients, reducing hospital admissions by 20-25%.
  • Applicable Scenarios: Young, low-comorbidity patients presenting with non-ischemic ECG and undetectable hs-cTnT, suitable for rapid discharge.
  • Implementation Considerations:
    • Training ED Staff on the new protocol.
    • Ensuring availability and reliability of hs-cTnT assays.
    • Integrating with existing clinical decision tools.
  • Integration with Existing Evidence: Aligns with ESC guidelines advocating for high-sensitivity troponins and accelerated MI exclusion protocols.

How To Use This Info In Practice

Practitioners should consider using an initial undetectable hs-cTnT level (<5 ng/l) combined with a non-ischemic ECG to safely discharge low-risk chest pain patients directly from the ED, thereby reducing unnecessary admissions without compromising patient safety.

Notes for Clarity

  • Statistical Significance: Highlighted with bold formatting (e.g., P < 0.05)
  • Confidence Intervals: Provided where available
  • Conflicts of Interest: Not reported
  • Areas of Uncertainty: Short-lived benefits and high side effect incidence
  • Funding Sources: Not specified