16.6: Myocarditis II: Clinical Features and Diagnostic Tests

Myocarditis is an inflammation of the heart muscle. The symptoms vary widely, encompassing asymptomatic presentations to severe, acute manifestations.

Clinical Presentation

Asymptomatic cases: In some instances, myocarditis may be asymptomatic, with the infection resolving without intervention. These cases often go undetected unless discovered incidentally through diagnostic imaging or tests conducted for other reasons.

General Early Symptoms: Early symptoms of myocarditis are non-specific and can mimic those of other viral infections. These include:

• Fever
• Fatigue
• Malaise
• Myalgias (muscle pain)
• Dyspnea (shortness of breath)
• Lymphadenopathy (swollen lymph nodes)
• Nausea and vomiting

Early cardiac signs

As myocarditis progresses, more specific cardiac symptoms may emerge, including:

• Pleuritic chest pain: Sharp pain that worsens with breathing.
• Pericardial friction rub: A scratchy or grating sound heard with a stethoscope, indicating inflammation of the pericardium.
• Pericardial effusion: The accumulation of fluid in the pericardial sac around the heart can be detected using medical imaging.

Diagnostic Approach

Medical history

A thorough medical history is essential, focusing on recent viral infections, travel history, and any underlying autoimmune diseases that may predispose an individual to myocarditis.

Physical examination

A physical examination may reveal several signs indicative of myocarditis:

• Arrhythmias: Irregular heartbeats detectable through auscultation or ECG.
• Crackles in the lungs: Suggestive of pulmonary congestion.
• Jugular venous distention: Indicative of increased central venous pressure.
• Syncope: Episodes of fainting, which may result from arrhythmias or cardiac dysfunction.
• Peripheral edema: Swelling of the limbs, a sign of advanced heart failure.

Laboratory tests

Laboratory investigations often show non-specific inflammatory markers and cardiac-specific enzymes:

• Mild to moderate leukocytosis: Increased white blood cell count.
• Atypical lymphocytes
• Elevated erythrocyte sedimentation rate (ESR)
• Increased C-reactive protein (CRP) levels
• Elevated cardiac biomarkers, such as troponin, indicate myocardial injury.

ECG Findings

Electrocardiograms (ECGs) can reveal abnormalities typical of myocarditis:

• Diffuse ST-segment changes
• T-wave inversions reflecting myocardial inflammation or injury.

Endomyocardial Biopsy

An endomyocardial biopsy may be performed for a definitive diagnosis, especially in acute cases. This procedure involves sampling myocardial tissue, which is then examined for:

• Lymphocytic infiltration: Indicative of an immune response.
• Myocyte damage: Evidence of direct myocardial injury.

Accurate and timely diagnosis of myocarditis is crucial for effective management. It involves a combination of clinical evaluation, laboratory testing, imaging, and, when necessary, Biopsy. This comprehensive approach ensures that myocarditis is identified and treated appropriately to prevent severe complications.