Myocarditis — SAQ

Stem

A 24-year-old male university student presents to the emergency department with pleuritic central chest pain that worsens on inspiration and improves when sitting forward. Two weeks earlier he had a febrile illness with sore throat, myalgia and loose stools, now resolved. On examination he is febrile (38.2 °C), heart rate 110/min, blood pressure 104/66 mmHg, oxygen saturation 97% on air. A three-component pericardial friction rub is audible at the left sternal border. ECG shows diffuse concave ST elevation in the anterior, lateral and inferior leads with PR depression in II and aVF. High-sensitivity troponin T is 850 ng/L (URL 14 ng/L). Chest X-ray shows a small cardiomegaly with clear lung fields. Echocardiography shows a mild pericardial effusion and mild global left ventricular impairment (LVEF 48%). Coronary angiography shows no obstructive coronary disease.

Questions

a) What is the most likely diagnosis, and what two syndromes does it overlap? (2 marks)

Acute viral perimyocarditis (myocarditis with concurrent pericarditis). It overlaps with acute pericarditis (diffuse ST elevation, PR depression, friction rub, pericardial effusion) and acute coronary syndrome / STEMI (raised troponin, ST elevation) — the normal coronary angiogram excludes obstructive coronary disease and points to myocarditis.

b) State the diagnostic imaging criteria that would confirm the diagnosis non-invasively, and reproduce them. (3 marks)

Cardiac MRI — Lake Louise Criteria. Original 2009 (Friedrich): diagnosis supported if 2 of 3 present — (i) regional wall-motion abnormality ± global dysfunction, (ii) myocardial oedema (T2 ratio of myocardium/skeletal muscle ≥ 1.8 or absolute T2 ≥ 59 ms), (iii) non-ischaemic late gadolinium enhancement (mid-wall/subepicardial, typically inferolateral, sparing subendocardium). Updated 2018 (Ferreira): at least one T2-based AND one T1-based criterion (T1/T2 mapping ≥ 2 SD above normal, increased extracellular volume fraction, or non-ischaemic LGE).

c) Outline the stepwise management. Include the specific drug classes to use and to avoid, with rationale. (3 marks)

• Admit, telemetry/CCU monitoring, serial troponin and ECG; treat pain.
• Avoid NSAIDs (worsen myocardial inflammation, raise blood pressure, retain sodium, worsen outcomes in myocarditis) — in contrast to their first-line role in isolated pericarditis. Use paracetamol for fever/pain.
• Heart-failure therapy (LVEF 48%): once haemodynamically stable start an ACE inhibitor (ramipril 2.5 mg PO once daily, titrate) and a beta-blocker (bisoprolol 2.5 mg PO once daily) once decongested; loop diuretic (furosemide 20 to 40 mg PO) if congested; MRA (spironolactone 12.5 to 25 mg PO) if symptomatic.
• For the pericardial component, colchicine 0.5 mg once/twice daily for 3 months may be used; NSAIDs only if LV function is normal.
• Strict activity restriction — no competitive sport, no moderate-to-vigorous exercise for 3 to 6 months.
• No immunosuppression in this typical lymphocytic viral case.

d) Describe the indications for endomyocardial biopsy in myocarditis, and what finding would change management in this patient? (2 marks)

Endomyocardial biopsy is indicated when it will change management: fulminant or rapidly progressive heart failure, new unexplained sustained ventricular arrhythmia or high-grade AV block (suspect giant cell myocarditis), refractory cardiogenic shock being considered for mechanical circulatory support or transplant, and suspected eosinophilic/drug-induced disease. In this stable, typical lymphocytic viral case, biopsy is not required; finding multinucleated giant cells would change management to cyclosporine + corticosteroids.