Is troponin indicated in a patient with tachycardia and dizziness, without shortness of breath (SOB) or chest pain (CP)?

Troponin Testing in Patients with Tachycardia and Dizziness Without SOB or CP

Troponin testing is indicated in patients with tachycardia and dizziness even in the absence of shortness of breath (SOB) or chest pain (CP), as these symptoms may represent atypical presentations of acute coronary syndrome (ACS). 1

Rationale for Troponin Testing

• Troponin has become the most widely used and well-validated diagnostic laboratory test for the diagnosis of myocardial ischemia and is the preferred biomarker for the international definition of myocardial infarction 1
• About one-third of patients admitted to the emergency department with acute chest pain have a normal ECG, yet among such patients, 5-40% have an evolving acute myocardial infarction 1
• A completely normal ECG does not exclude the possibility of NSTE-ACS, particularly in the territory of the circumflex artery or isolated right ventricular ischemia 1
• Almost two-thirds of all ischemic episodes in the phase of instability are clinically silent, and hence are unlikely to be detected by a conventional ECG 1

Clinical Decision Pathways for Acute Presentations

• Clinical decision pathways should categorize patients into low-, intermediate-, and high-risk strata to facilitate disposition and subsequent diagnostic evaluation 1
• Tachycardia is a common sign in patients with ACS and can be the primary presenting symptom even without typical chest pain 1
• Dizziness may represent hemodynamic compromise or an atypical presentation of ACS, particularly in certain populations (elderly, women, diabetics) 1

Troponin Elevation in Non-ACS Conditions

• While troponin accurately identifies myocardial necrosis, it does not inform as to the cause, which can include:
  • Tachyarrhythmias (including supraventricular tachycardia) 2, 3, 4, 5
  • Heart failure (acute and chronic) 1
  • Pulmonary embolism 1
  • Myocarditis 1
  • Takotsubo cardiomyopathy 6
  • Renal dysfunction 1

Importance of Serial Testing

• For high-sensitivity troponin assays, recommended time intervals after the initial troponin sample collection for repeat measurements are 1 to 3 hours 1
• For conventional troponin assays, repeat measurements should be taken at 3 to 6 hours 1
• A single negative high-sensitivity troponin test may be sufficient to exclude myocardial injury if symptoms began at least 3 hours before presentation 1

Interpretation of Results

• The diagnostic cut-off for MI is defined as a cardiac troponin measurement exceeding the 99th percentile of a normal reference population (upper reference limit) 1
• In patients with tachycardia, troponin elevation may occur due to:
  • Supply-demand mismatch causing myocardial injury 5
  • Underlying coronary artery disease unmasked by increased heart rate 1
  • Direct myocardial stress from the tachycardia itself 2, 3, 4

Clinical Approach

• Obtain serial ECGs to monitor for dynamic changes, which increase risk assessment 7
• Consider additional ECG leads (V7-V9) if standard leads are inconclusive 7
• Perform serial troponin measurements to establish a rising or falling pattern, which helps distinguish acute from chronic injury 7
• Echocardiography is recommended to evaluate regional wall motion abnormalities and rule out alternative diagnoses 7

Common Pitfalls and Caveats

• Elevated troponin in the setting of tachycardia without coronary artery disease occurs in up to 10-15% of cases 3
• Troponin release may occur from the free cytosolic pool of myocytes without structural damage due to changes in membrane permeability 3
• The association between troponin elevation in isolated tachyarrhythmias and adverse cardiovascular events appears to be very low 5
• Avoid premature exclusion of ACS based solely on absence of typical symptoms, as atypical presentations are common 1

In conclusion, troponin testing is indicated in patients presenting with tachycardia and dizziness even without SOB or CP, as these may represent atypical presentations of ACS. The results should be interpreted in the clinical context, with consideration of both cardiac and non-cardiac causes of troponin elevation.