Should a troponin enzyme level be checked in a patient presenting with syncope?

Troponin Testing in Syncope

Routine troponin testing should NOT be performed in all patients presenting with syncope; instead, troponin measurement should be reserved for patients in whom acute myocardial infarction is specifically suspected based on clinical assessment, history, physical examination, and ECG findings. 1

Guideline Recommendations

The 2017 ACC/AHA/HRS Syncope Guidelines provide clear direction on troponin testing:

• Class IIb recommendation (uncertain usefulness) for high-sensitivity troponin measurement in patients with suspected cardiac causes of syncope 1

• Class III recommendation (no benefit) for routine and comprehensive laboratory testing, including troponin, in the evaluation of all patients with syncope 1

• Class IIa recommendation supports targeted blood tests only when identified on the basis of clinical assessment from history, physical examination, and ECG 1

Clinical Decision Algorithm

When to Check Troponin:

Check troponin if ANY of the following are present:

• ECG shows ischemic changes (ST-segment deviation, pathological Q waves, or new T-wave inversions) 2
• Symptoms suggestive of acute coronary syndrome (chest pain, dyspnea, diaphoresis) 1
• Known coronary artery disease with exertional syncope 1
• Syncope associated with palpitations in a patient with cardiac history 1

When NOT to Check Troponin:

Do not check troponin in:

• Classic vasovagal syncope with clear prodrome (nausea, diaphoresis, warmth) and typical triggers 1
• Orthostatic hypotension with documented blood pressure changes 1
• Young patients without cardiac history or risk factors and normal ECG 1

Evidence Supporting Selective Testing

The systematic review cited in the guidelines found little value in contemporary troponin measurement unless acute myocardial infarction is suspected 1. This is reinforced by research data:

• AMI occurs in only 1.4% of syncope patients, and all cases had ischemic ECG changes at presentation 2
• The presenting ECG was 100% sensitive with 100% negative predictive value for AMI in syncope patients 2
• Troponin provides little additional benefit beyond the ECG for identifying AMI-related syncope 2

Prognostic Value vs. Diagnostic Value

While troponin has limited diagnostic utility for determining the cause of syncope, it does carry prognostic significance:

• Elevated troponin predicts 1-month serious outcomes or death (50% vs. 6% in those without elevation) 2
• Higher troponin concentrations correlate with increasing risk of adverse events at 1 month (0%, 9%, 13%, 26%, 70% across quintiles) and 1 year (10%, 22%, 26%, 52%, 85%) 3
• Diagnostic accuracy for cardiac syncope is modest (AUC 0.77), with only 52% likelihood of adverse events in those with elevated levels 4

However, the ability of troponin measurement to influence clinical decision-making or patient outcomes remains unknown 1

Critical Pitfalls to Avoid

• Do not use troponin to rule out AMI in isolated syncope without other features suggesting acute coronary syndrome 2
• Do not order serial troponins based solely on an initial elevation in syncope patients, as serial testing provides little additional value 5
• Do not dismiss mildly elevated troponin as clinically insignificant, as even small elevations carry prognostic weight 6, 3
• Do not rely on troponin alone without considering the clinical context and ECG findings 4

Practical Approach

Start with ECG interpretation:

• Normal ECG in young patient with typical vasovagal features → No troponin needed 1, 2
• Ischemic ECG changes → Check troponin and pursue cardiac evaluation 2
• Abnormal ECG suggesting structural disease or arrhythmia → Consider echocardiography rather than troponin 1

If troponin is checked and elevated:

• Pursue cardiac evaluation with echocardiography and cardiology consultation 6
• Recognize this indicates higher risk regardless of whether it explains the syncope mechanism 3, 4
• A threshold of >50 ng/L is more clinically meaningful for determining need for cardiac workup 5