ESC 0/1‑Hour High‑Sensitivity Troponin Algorithm for Acute Chest Pain

Algorithm Selection and Timing

• The 2021 European Society of Cardiology (ESC) guidelines designate the 0‑/1‑hour high‑sensitivity cardiac troponin (hs‑cTn) protocol as the preferred strategy for rapid rule‑out/rule‑in of myocardial infarction (MI); the 0‑/2‑hour protocol is the secondary option. 1
• The 2022 American College of Cardiology (ACC) consensus acknowledges multiple validated pathways and highlights that the 0‑/1‑hour algorithm leverages superior assay sensitivity and precision, allowing the largest proportion of patients to be safely ruled out. 2
• Precise timing is essential: the second blood sample must be drawn exactly 1 hour after the initial draw for the 0‑/1‑hour algorithm to remain valid. 1, 2
• When a 1‑hour draw cannot be reliably performed, institutions should adopt the 0‑/2‑hour algorithm as a practical alternative. 2, 3

Rule‑Out Pathway (Low‑Risk)

• Patients are ruled out when either (a) a very low baseline hs‑cTn (Roche < 5 ng/L, Abbott < 4 ng/L, Siemens < 3 ng/L) or (b) a low baseline hs‑cTn (Roche < 12 ng/L, Abbott < 5 ng/L, Siemens < 6 ng/L) plus a minimal 1‑hour delta (Roche < 3 ng/L, Abbott < 2 ng/L, Siemens < 3 ng/L). 1
• In validation cohorts this rule‑out pathway yields a negative predictive value > 99 % for MI, permitting safe discharge with outpatient follow‑up. 1
• The very‑low baseline rule‑out is applicable only when chest‑pain onset occurred more than 3 hours before presentation; earlier presenters require the full serial 0‑ and 1‑hour assessment. 1

Rule‑In Pathway (High‑Risk)

• Patients are ruled in when either (a) a high baseline hs‑cTn (Roche ≥ 52 ng/L, Abbott ≥ 64 ng/L, Siemens ≥ 120 ng/L) or (b) a significant 1‑hour delta (Roche ≥ 5 ng/L, Abbott ≥ 6 ng/L, Siemens ≥ 12 ng/L). 1
• The rule‑in group has an approximate positive predictive value of 75 % for MI. 1
• Most rule‑in patients without MI have conditions (e.g., coronary artery disease requiring angiography, Takotsubo syndrome, myocarditis) that merit admission to a coronary‑care unit and early imaging. 1

Observation Zone (Intermediate‑Risk)

• Patients not meeting rule‑out or rule‑in criteria are placed in an observation zone and should undergo further risk stratification using clinical scores such as HEART or TIMI. 4

Alternative Protocols

0‑/2‑Hour Algorithm

• Mirrors the three‑pathway logic of the 0‑/1‑hour protocol but uses a second draw at 2 hours. 2, 3
• Preferred for very early presenters (< 2 hours from symptom onset) because the longer interval reduces false‑negative results on the early rising limb of troponin release. 2, 3

0‑/3‑Hour Algorithm

• Employs a single hs‑cTn measurement below the 99th percentile if symptoms began > 6 hours ago and the patient is pain‑free; otherwise both 0‑ and 3‑hour values must be < 99th percentile. 2, 3, 5, 6
• Demonstrates lower sensitivity and negative predictive value than the 0‑/1‑hour or 0‑/2‑hour protocols, resulting in fewer patients being ruled out. 2, 3, 5, 6
• The 2021 ESC notes that three recent large studies show the 0‑/3‑hour algorithm balances efficacy and safety less favorably than the 0‑/1‑hour protocol. 1

Assay‑Specific Cutoffs for the 0‑/1‑Hour Algorithm

These cutoffs are assay‑specific and must be applied exactly as validated; they are not interchangeable across platforms. 1

Common Pitfalls and Mitigation

• Timing errors: Do not use emergency‑department arrival time as “time 0.” Exact 1‑hour intervals between draws are required; a sample taken at 55 min or 75 min invalidates the algorithm’s cutoffs. 1, 2
• Early presenters: The very‑low baseline rule‑out must not be applied when symptom onset is < 3 hours; these patients need the full serial 0‑ and 1‑hour assessment. 1
• Late presenters on the declining curve: The 0‑/1‑hour algorithm may miss MI in patients presenting > 12 hours after symptom onset with flat troponin kinetics; consider extending observation and repeating troponin at 3–6 hours. 2, 3
• Non‑ACS troponin elevation: Elevated hs‑cTn is non‑specific (e.g., heart failure, pulmonary embolism, myocarditis, renal failure, sepsis). The rule‑in pathway identifies myocardial injury, not necessarily acute coronary syndrome; integrate ECG, echocardiography, and clinical context. 1
• Chronic troponin elevation: In chronic kidney disease, heart failure, or stable coronary disease, baseline troponin may exceed the 99th percentile; diagnostic thresholds rely on relative change (e.g., ≥ 20 % rise) rather than absolute values. 4

Implementation Evidence

• Real‑world implementation studies, including a randomized controlled trial, have demonstrated very high safety and efficacy of the ESC 0‑/1‑hour algorithm when applied in routine emergency‑department practice. 1

Troponin Monitoring Protocol for Acute Chest Pain

Initial Assessment

• Obtain the first troponin measurement immediately at presentation (time 0) for every patient with symptoms suggestive of acute coronary syndrome. American College of Cardiology recommendation. 7, 8, 9
• When the exact symptom onset time is unclear, use the emergency‑department arrival time as the reference “time 0” for troponin sampling. American College of Cardiology guidance. 7, 8, 9

Timing of Repeat Measurements

Conventional Troponin Assays

• Repeat troponin testing 3–6 hours after the initial (time 0) draw. This interval captures myocardial injury that may be missed on an early normal result. American College of Cardiology protocol. 7, 8, 9
• A normal troponin at presentation does not rule out myocardial injury within the first 6 hours of symptom onset. American Heart Association evidence. 10

High‑Sensitivity Troponin Assays

• Repeat troponin testing 1–3 hours after the initial draw when using high‑sensitivity assays. American College of Cardiology recommendation. 7
• The 0/1‑hour algorithm uses the absolute troponin value at presentation and the change at 1 hour to rule‑in or rule‑out myocardial infarction. American College of Cardiology algorithm. 11
• The 0/2‑hour algorithm relies on the absolute values at 0 hours and the change at 2 hours for the same purpose. American Heart Association algorithm. 12, 11

Extended Monitoring for High‑Risk Patients

• Obtain additional troponin measurements beyond 6 hours in patients who initially have normal serial troponins but exhibit any of the following:
  
  • Electrocardiographic changes suggestive of ischemia,
  • Intermediate or high clinical risk features,
  • Persistent or recurrent chest pain. American Heart Association guidance. 8, 9, 10
• Serial testing at 3 hours, 6 hours, and optionally at 6–10 hours after presentation is required to definitively exclude myocardial injury. American Heart Association evidence. 10

Low‑Risk Patient Discharge Criteria

• In patients whose symptoms began ≥3 hours before ED arrival, a single high‑sensitivity troponin below the assay’s limit of detection at presentation is sufficient to exclude myocardial injury. American College of Cardiology recommendation. 7
• Patients meeting low‑risk criteria (TIMI score 0, normal ECG, negative troponins at 0 and 2 hours) have a 30‑day negative predictive value > 99 % for acute coronary syndrome. American College of Cardiology data. 13

Interpretation of Serial Troponin Changes

• A ≥20 % increase or decrease between serial measurements (when the initial value is already elevated) is required to diagnose acute myocardial injury. American Heart Association interpretation guideline. 14
• At least one troponin value must exceed the 99th‑percentile upper reference limit to confirm acute myocardial injury. American Heart Association criterion. 14
• A single pair of troponin values is insufficient; 10–15 % of patients with acute coronary syndrome may be missed if only one early pair is used. American Heart Association observation. 14
• Do not rely on a single normal troponin drawn within 6 hours of symptom onset to exclude myocardial infarction. American Heart Association warning. 10
• Troponin elevation is non‑specific and may occur in heart failure, pulmonary embolism, renal failure, and other conditions; therefore, clinical context is essential. American Heart Association clarification. 10
• Point‑of‑care troponin devices are generally less sensitive than central laboratory analyzers and may miss minor elevations. American Heart Association caution. 10
• In chronic conditions (e.g., heart failure, chronic kidney disease, stable coronary disease), mildly elevated baseline troponins are common; serial trend rather than absolute value guides diagnosis. American Heart Association recommendation. 14
• High‑sensitivity assays detect troponin in most healthy individuals, making serial change more diagnostically important than a single absolute value. American Heart Association insight. 14
• A change <20 % does not satisfy the diagnostic threshold for acute injury. American Heart Association standard. 14

Institutional Implementation

• Hospitals should adopt a standardized chest‑pain protocol that specifies troponin sampling intervals according to the assay type (conventional vs. high‑sensitivity). American College of Cardiology implementation guideline. 7
• Central laboratory turnaround time for troponin results should be ≤ 1 hour to enable timely clinical decision‑making. American Heart Association operational recommendation. 10