How can I differentiate myocarditis from other causes of acute chest pain in a primary care setting?

To differentiate myocarditis from other causes of acute chest pain in a primary care setting, focus on clinical features, examination, and initial investigations:

• Clinical history: Take a detailed history including pain characteristics (location, radiation, severity, duration, frequency), associated symptoms (such as breathlessness, palpitations, or recent viral illness), and cardiovascular risk factors or prior cardiac disease. Myocarditis often presents with chest pain that may mimic acute coronary syndrome but can be associated with recent infection or systemic symptoms ².
• Physical examination: Assess for signs of heart failure, arrhythmias, or pericardial rub which may suggest myocarditis rather than other causes like musculoskeletal pain or stable angina ²,¹.
• Initial investigations: In primary care, a resting 12-lead ECG can help identify abnormalities suggestive of myocarditis (e.g., diffuse ST changes) but is not definitive. Normal ECG does not exclude myocarditis ². Blood tests including troponin may be elevated in myocarditis but are more commonly used in hospital settings. If myocarditis is suspected or diagnosis is unclear, urgent referral for hospital assessment including cardiac biomarkers, echocardiography, and possibly cardiac MRI is recommended ²,¹.
• Differential diagnosis: Exclude acute coronary syndrome by ECG and clinical assessment. Consider other causes such as musculoskeletal pain, pulmonary embolism, pericarditis, or gastroesophageal reflux disease based on history and examination ¹,².
• Referral: If myocarditis is suspected or the cause of chest pain is unclear and serious pathology cannot be excluded, arrange urgent hospital referral for further assessment ¹,².

Summary: In primary care, myocarditis differentiation relies on careful history, examination, ECG, and clinical judgement. Definitive diagnosis requires hospital-based investigations. Urgent referral is warranted if myocarditis or other serious causes are suspected ¹,².