What is the recommended protocol for managing patients with suspected acute myocardial infarction using the high-sensitivity (HS) troponin pathway?

From the Guidelines

The recommended protocol for managing patients with suspected acute myocardial infarction using the high-sensitivity (HS) troponin pathway involves a 0/1-h rule-out algorithm, which takes advantage of better assay sensitivity and precision, allowing for earlier rule-out of low-risk patients. This approach is supported by the most recent evidence from the 2022 ACC expert consensus decision pathway on the evaluation and disposition of acute chest pain in the emergency department 1.

Key Components of the Protocol

• Obtain an ECG and baseline HS-troponin measurement upon patient presentation with chest pain or symptoms suggestive of AMI.
• If the initial troponin is elevated above the 99th percentile upper reference limit, consider this a positive result warranting further evaluation for AMI.
• For patients with non-elevated initial values, repeat HS-troponin testing at 1 hour after presentation.
• Use baseline (0-h) and delta values at 1 hour to assign patients to the rule-out, observation, or abnormal groups.
• A significant rise or an absolute change exceeding assay-specific delta values indicates likely AMI.

Advantages of the 0/1-h Rule-Out Algorithm

• Takes advantage of better assay sensitivity and precision
• Allows for earlier rule-out of low-risk patients
• Reduces the delay to diagnosis and translates into shorter stays in the emergency department and lower costs

Considerations for Implementation

• The cut-off levels within the 0/1-h algorithm are assay-specific.
• The timing of blood draws is very important.
• The algorithm should always be integrated with a detailed clinical assessment.
• Patients with negative serial troponins and no concerning ECG changes can often be safely discharged with appropriate follow-up.
• During evaluation, administer aspirin, consider anticoagulation, and provide supplemental oxygen if necessary, as recommended by previous guidelines 1.

This approach prioritizes morbidity, mortality, and quality of life by allowing for rapid and accurate diagnosis of AMI, while also reducing unnecessary hospitalizations and costs. The specific delta values and timing may vary slightly based on the particular HS-troponin assay used at your institution, as noted in the 2016 ESC guidelines for the management of acute coronary syndromes 1.

From the Research

HS Troponin Pathway for Managing Patients with Suspected Acute Myocardial Infarction

The high-sensitivity (HS) troponin pathway is a recommended protocol for managing patients with suspected acute myocardial infarction (AMI). This protocol involves measuring HS troponin levels at presentation and after a certain period, usually 1-3 hours, to diagnose or rule out AMI.

Key Findings

• A 2-hour algorithm using HS troponin T can classify 60% of patients as "rule-out," 16% as "rule-in," and 24% in the "observational-zone" with a sensitivity of 99.5% and negative predictive value (NPV) of 99.9% for rule-out, and specificity of 96% and positive predictive value (PPV) of 78% for rule-in 2.
• Using a high baseline HS troponin I concentration of 150 ng/L can result in a PPV of 87.8% for the diagnosis of AMI, while a HS troponin I change of 20 ng/L after 1 hour can result in a PPV of 86.5% 3.
• A 0/2-h algorithm using the HS cardiac troponin I assay can rule out 55% of patients with a NPV of 99.8% and sensitivity of 99.4%, and rule in 30% of patients with a PPV of 73% 4.
• A single HS troponin I measurement on admission combined with a low-risk electrocardiogram (ECG) can safely rule out AMI without the need for serial troponin testing, with a NPV of 100% 5.
• The European Society of Cardiology (ESC) 0/1-hour and 0/2-hour algorithms have higher sensitivities and NPVs than the 0/3-hour algorithm for index AMI, with pooled sensitivities of 99.1% and 98.6%, and NPVs of 99.8% and 99.6%, respectively 6.

Diagnostic Algorithms

• The 2-hour algorithm using HS troponin T:
  • Rule-out: HS troponin T < 14 ng/L at presentation and absolute change < 10 ng/L within 2 hours
  • Rule-in: HS troponin T ≥ 52 ng/L at presentation or absolute change ≥ 10 ng/L within 2 hours
• The 0/2-h algorithm using the HS cardiac troponin I assay:
  • Rule-out: 0-h HS troponin I < 4 ng/L in patients with onset of chest pain > 3 hours, or 0-h HS troponin I < 5 ng/L and absolute change < 5 ng/L within 2 hours
  • Rule-in: 0-h HS troponin I ≥ 50 ng/L or absolute change ≥ 20 ng/L within 2 hours

Clinical Implications

• The HS troponin pathway can help rapidly diagnose or rule out AMI, reducing the need for prolonged monitoring and serial blood sampling.
• The choice of algorithm and assay may depend on the specific clinical context and available resources.
• Clinicians should consider the results of these studies when developing protocols for managing patients with suspected AMI.