Overview
Definition:
Myocarditis is inflammation of the heart muscle, often triggered by viral infections, leading to impaired cardiac function
In adolescents, post-viral myocarditis presents a diagnostic challenge, especially when chest pain is the primary symptom.
Epidemiology:
While the exact incidence in adolescents is hard to pinpoint, viral infections are the most common cause of myocarditis globally
Surveys suggest a higher prevalence in males
It can occur in otherwise healthy individuals following a preceding viral prodrome.
Clinical Significance:
Accurate and timely diagnosis of myocarditis is crucial in adolescents due to the potential for acute complications like heart failure, arrhythmias, and even sudden cardiac death
Early recognition and management can significantly improve outcomes and prevent long-term sequelae.
Clinical Presentation
Symptoms:
Chest pain, often non-pleuritic and dull or aching
Shortness of breath (dyspnea) on exertion or at rest
Palpitations or awareness of heart rhythm
Fatigue or reduced exercise tolerance
Fever or flu-like symptoms preceding chest pain
Nausea, vomiting, or abdominal pain.
Signs:
Tachycardia or bradycardia
Irregular pulse
Gallop rhythm (S3 or S4)
Murmurs of mitral regurgitation
Signs of heart failure: tachypnea, grunting, crackles on lung auscultation, hepatomegaly, peripheral edema
Hypotension or signs of shock in severe cases.
Diagnostic Criteria:
No single definitive diagnostic criterion exists for myocarditis
Diagnosis is typically based on a combination of clinical suspicion, characteristic ECG changes, elevated cardiac biomarkers, imaging findings, and often endomyocardial biopsy (though this is invasive and not routinely performed in all cases).
Diagnostic Approach
History Taking:
Detailed history of recent viral illness (URI, gastroenteritis, fever)
Onset, character, and duration of chest pain
Associated symptoms like dyspnea, palpitations, syncope
History of known cardiac conditions or autoimmune diseases
Family history of sudden cardiac death or cardiomyopathy
Recent travel or exposure to infectious agents.
Physical Examination:
Comprehensive cardiovascular examination including auscultation for murmurs, gallops, and rubs
Assessment for jugular venous distension, peripheral edema, and hepatomegaly
Evaluation of respiratory status and skin perfusion
Neurological assessment for any signs of central nervous system involvement (rare).
Investigations:
Electrocardiogram (ECG): may show sinus tachycardia, ST-segment changes (diffuse or localized), T-wave inversions, or conduction abnormalities
Cardiac biomarkers: Elevated troponin I or T is sensitive and specific for myocardial injury
Elevated CK-MB may also be seen
Brain natriuretic peptide (BNP) or N-terminal pro-BNP (NT-proBNP) may be elevated in heart failure
Echocardiogram: to assess ventricular function, wall motion abnormalities, chamber dilation, valvular function, and pericardial effusion
Cardiac MRI (CMR): considered the gold standard for non-invasive diagnosis, showing myocardial edema, inflammation, and late gadolinium enhancement
Viral serology: may identify specific causative viruses (e.g., enteroviruses, adenovirus, parvovirus B19, influenza, COVID-19), though often non-specific or retrospective
Complete blood count (CBC) with differential: may show leukocytosis
Inflammatory markers: ESR and CRP can be elevated but are non-specific
Polymerase Chain Reaction (PCR) on blood or tissue: can detect viral RNA/DNA
Endomyocardial biopsy: historically the gold standard, showing inflammatory infiltrates and myocyte necrosis, but limited by sampling error and invasiveness.
Differential Diagnosis:
Pericarditis: typically pleuritic chest pain, positional, relieved by sitting up and leaning forward
friction rub may be present
Musculoskeletal pain: often reproducible with palpation or movement
Anxiety/panic attack: hyperventilation, pallor, diaphoresis
Pulmonary embolism: sudden onset dyspnea, pleuritic chest pain, risk factors for VTE
Pneumonia: cough, fever, consolidation on chest X-ray
Gastroesophageal reflux disease (GERD): burning chest pain, postprandial exacerbation
Coronary artery anomalies or vasospasm: rarer causes of chest pain in adolescents
Psychiatric causes of somatization.
Management
Initial Management:
Assessment of hemodynamic stability and respiratory status
Prompt recognition of shock or severe heart failure
Hospitalization is usually indicated for suspected myocarditis
Supportive care includes oxygen therapy, intravenous fluids (cautiously to avoid overload), and monitoring of vital signs and urine output.
Medical Management:
Supportive care for heart failure: diuretics (e.g., furosemide), ACE inhibitors, beta-blockers (if hemodynamically stable), and aldosterone antagonists
Inotropic support (e.g., dobutamine, milrinone) may be required for cardiogenic shock
Arrhythmia management: antiarrhythmics may be necessary
Immunosuppression: Generally not indicated for viral myocarditis unless autoimmune etiology is suspected or in specific cases of giant cell myocarditis or eosinophilic myocarditis, guided by biopsy results.
Surgical Management:
Rarely indicated for uncomplicated myocarditis
Mechanical circulatory support (e.g., ECMO, ventricular assist devices) may be considered in refractory cardiogenic shock
Heart transplantation is a last resort for end-stage cardiac failure unresponsive to medical therapy.
Supportive Care:
Strict bed rest during the acute phase, with gradual increase in activity as symptoms improve and cardiac function normalizes
Cardiac monitoring with continuous ECG
Fluid and electrolyte balance
Nutritional support
Management of fever and pain
Psychological support for the patient and family.
Complications
Early Complications:
Acute heart failure with pulmonary edema
Cardiogenic shock
Life-threatening arrhythmias (e.g., ventricular tachycardia, ventricular fibrillation)
Myocardial rupture (rare)
Pericarditis or pericardial effusion.
Late Complications:
Dilated cardiomyopathy
Chronic heart failure
Persistent arrhythmias
Mural thrombus formation
Sudden cardiac death
Idiopathic dilated cardiomyopathy if the underlying cause is not identified or treated.
Prevention Strategies:
Prevention of viral infections through vaccination (e.g., influenza, COVID-19)
Prompt management of viral illnesses
Early recognition and referral of suspected myocarditis cases to tertiary care centers
Close follow-up to monitor for chronic cardiac dysfunction.
Prognosis
Factors Affecting Prognosis:
Severity of myocardial injury
Degree of ventricular dysfunction
Presence of arrhythmias or heart failure
Etiology of myocarditis (some viruses are associated with worse outcomes)
Promptness of diagnosis and initiation of management
Age of the patient.
Outcomes:
Prognosis varies widely
Many children and adolescents with mild to moderate myocarditis recover full cardiac function
However, a significant proportion may develop chronic dilated cardiomyopathy
Mortality rates are highest in severe cases with cardiogenic shock.
Follow Up:
Regular clinical and echocardiographic follow-up is essential to monitor for recovery of cardiac function, development of arrhythmias, or progression to dilated cardiomyopathy
Exercise stress testing may be indicated to assess functional capacity and identify exercise-induced arrhythmias
Long-term management of heart failure may be required.
Key Points
Exam Focus:
Viral prodrome preceding chest pain is a key feature
ECG changes can be variable
Troponin and echocardiogram are crucial initial investigations
Cardiac MRI is highly sensitive for diagnosis
Management is primarily supportive with attention to heart failure and arrhythmias
Differentiate from pericarditis.
Clinical Pearls:
Always consider myocarditis in a teenager with new-onset chest pain and preceding viral symptoms, especially if they have any signs of heart failure or arrhythmias
Don't dismiss chest pain as purely anxiety in this demographic
Serial ECGs and troponins can be more informative than a single measurement.
Common Mistakes:
Attributing chest pain solely to musculoskeletal or psychological causes without adequate cardiac evaluation
Delaying investigation in hemodynamically unstable patients
Inappropriate fluid management in patients with impaired cardiac function
Overlooking arrhythmias on monitoring
Underestimating the potential for long-term sequelae.