Myocarditis

Overview

Myocarditis represents a significant cause of cardiovascular morbidity and mortality, particularly in young adults and children. The condition occurs when the heart muscle becomes inflamed due to an infection, autoimmune response, or exposure to toxins. This inflammation can damage the heart muscle cells and the heart's electrical system, disrupting the normal pumping action and rhythm of the heart.

The incidence of myocarditis is difficult to determine precisely because many cases are subclinical or go undiagnosed. Studies suggest it affects approximately 10-20 per 100,000 individuals annually, though this may be an underestimate. The condition has gained increased attention recently due to rare cases associated with COVID-19 infection and, even more rarely, with COVID-19 vaccination, though the risk from the virus itself is significantly higher than from vaccination.

The presentation of myocarditis varies widely, from asymptomatic cases discovered incidentally to fulminant myocarditis requiring immediate intensive care. The prognosis depends on the cause, extent of myocardial damage, and promptness of treatment. While many patients recover completely, some develop chronic heart failure or dilated cardiomyopathy. Understanding the diverse causes, recognizing symptoms early, and implementing appropriate treatment strategies are crucial for optimal outcomes.

Symptoms

The symptoms of myocarditis can range from none at all to life-threatening heart failure. The presentation often depends on the extent and location of inflammation, the underlying cause, and individual patient factors. Symptoms may develop suddenly or progress gradually over days to weeks.

Common Cardiac Symptoms

• Sharp chest pain - Often positional, may mimic heart attack pain
• Palpitations - Sensation of rapid, fluttering, or pounding heartbeat
• Dizziness - Due to irregular heart rhythms or reduced cardiac output
• Shortness of breath - At rest or during physical activity
• Fatigue and weakness - Often disproportionate to activity level
• Swelling in legs, ankles, and feet (edema)

Systemic Symptoms

• Fever and chills - Common with infectious causes
• Flu-like symptoms - Body aches, headache, joint pain
• Sore throat or respiratory symptoms - May precede cardiac symptoms
• Gastrointestinal symptoms - Nausea, vomiting, diarrhea
• Decreased appetite and weight loss
• Night sweats

Symptoms of Complications

• Sudden loss of consciousness (syncope)
• Rapid breathing or difficulty breathing when lying flat
• Blue or gray skin color (cyanosis)
• Decreased urine output
• Confusion or altered mental status
• Cold, clammy extremities

Pediatric Symptoms

Children with myocarditis may present differently than adults:

• Poor feeding or appetite in infants
• Irritability or listlessness
• Breathing difficulties or grunting
• Pale or bluish skin color
• Reduced activity or play
• Failure to thrive

It's important to note that myocarditis symptoms can mimic many other conditions, including acute coronary syndrome, making diagnosis challenging. The combination of recent viral illness followed by cardiac symptoms should raise suspicion for myocarditis.

Causes

Myocarditis can result from various infectious and non-infectious causes. Understanding the underlying etiology is important for guiding treatment and determining prognosis.

Viral Infections (Most Common)

• Coxsackievirus B: Most common viral cause in many regions
• Adenovirus: Common in children and military recruits
• Parvovirus B19: Can cause severe myocarditis
• Human herpesvirus 6: Associated with myocarditis in immunocompromised
• Epstein-Barr virus: Usually mild myocardial involvement
• Cytomegalovirus: Particularly in immunosuppressed patients
• Influenza virus: Can cause severe myocarditis during epidemics
• HIV: Both direct viral effect and opportunistic infections
• SARS-CoV-2: COVID-19 associated myocarditis

Bacterial Infections

• Streptococcus: Rheumatic fever and direct infection
• Staphylococcus: Often associated with sepsis
• Corynebacterium diphtheriae: Diphtheria myocarditis
• Borrelia burgdorferi: Lyme carditis
• Rickettsia: Various rickettsial diseases
• Mycoplasma pneumoniae: Rare but reported

Other Infectious Causes

• Parasitic: Trypanosoma cruzi (Chagas disease), toxoplasmosis
• Fungal: Aspergillus, Candida (in immunocompromised)
• Protozoal: Malaria in endemic areas

Non-Infectious Causes

• Autoimmune diseases:
  • Systemic lupus erythematosus
  • Sarcoidosis
  • Giant cell myocarditis
  • Eosinophilic myocarditis
• Drug-induced:
  • Chemotherapy agents (doxorubicin, cyclophosphamide)
  • Antibiotics (penicillin, sulfonamides)
  • Antipsychotics (clozapine)
  • Immune checkpoint inhibitors
• Toxins:
  • Alcohol
  • Cocaine and amphetamines
  • Heavy metals (lead, copper)
  • Carbon monoxide
• Physical agents: Radiation therapy, electric shock
• Vaccines: Rare cases, particularly smallpox vaccine

Risk Factors

Several factors can increase the likelihood of developing myocarditis:

• Age: Can occur at any age but most common in young adults (20-40 years)
• Gender: Men are affected more often than women (1.5:1 ratio)
• Recent viral infection: Upper respiratory or gastrointestinal illness
• Immunosuppression: HIV/AIDS, organ transplant, chemotherapy
• Autoimmune diseases: Lupus, rheumatoid arthritis, sarcoidosis
• Pregnancy: Peripartum cardiomyopathy risk
• Genetic factors: Family history of cardiomyopathy or sudden death
• Previous myocarditis: Risk of recurrence
• Geographic location: Endemic areas for Chagas disease
• Substance abuse: Cocaine, amphetamines, alcohol
• Certain medications: Some drugs carry higher risk
• Environmental exposures: Radiation, toxins
• Athletic participation: Intense exercise during acute infection

Diagnosis

Diagnosing myocarditis can be challenging due to its variable presentation and overlap with other cardiac conditions. A combination of clinical assessment, laboratory tests, imaging, and sometimes tissue diagnosis is required.

Clinical Evaluation

• Medical history: Recent infections, medications, travel, family history
• Physical examination: Heart sounds, signs of heart failure, arrhythmias
• Vital signs: Tachycardia, hypotension, fever
• Cardiac auscultation: S3 gallop, murmurs, pericardial friction rub

Laboratory Tests

• Cardiac biomarkers:
  • Troponin I or T (elevated in myocardial injury)
  • Brain natriuretic peptide (BNP) or NT-proBNP
  • Creatine kinase-MB (CK-MB)
• Inflammatory markers: ESR, C-reactive protein
• Complete blood count: Leukocytosis, eosinophilia
• Viral studies: PCR, serology for specific viruses
• Autoimmune markers: If autoimmune cause suspected

Electrocardiogram (ECG)

• ST segment changes (elevation or depression)
• T wave abnormalities
• Arrhythmias (PVCs, VT, heart block)
• Low voltage QRS complexes
• Q waves (rare, suggests extensive necrosis)

Imaging Studies

• Echocardiography:
  • Wall motion abnormalities
  • Reduced ejection fraction
  • Chamber dilation
  • Pericardial effusion
  • Diastolic dysfunction
• Cardiac MRI (Gold standard non-invasive test):
  • Late gadolinium enhancement
  • T2-weighted imaging for edema
  • T1 mapping for fibrosis
  • Functional assessment
• Chest X-ray: Cardiomegaly, pulmonary edema
• Nuclear imaging: Gallium-67 or FDG-PET for inflammation

Endomyocardial Biopsy

• Gold standard for definitive diagnosis
• Indicated in severe cases or uncertain diagnosis
• Dallas criteria for histologic diagnosis
• Immunohistochemistry for viral genomes
• Risk of complications limits routine use

Diagnostic Criteria

The diagnosis often relies on a combination of:

• Clinical presentation consistent with myocarditis
• Evidence of myocardial injury (biomarkers, ECG changes)
• Imaging findings suggestive of inflammation
• Exclusion of other causes (coronary disease, valve disease)

Treatment Options

Treatment of myocarditis depends on the severity of symptoms, underlying cause, and presence of complications. Management ranges from supportive care to advanced mechanical support and transplantation.

General Management

• Activity restriction: Avoid competitive sports for 3-6 months
• Cardiac monitoring: Continuous telemetry for arrhythmias
• Fluid and sodium restriction: In heart failure
• Oxygen therapy: As needed for hypoxemia
• Avoid cardiotoxic drugs: NSAIDs, certain antibiotics

Heart Failure Management

• ACE inhibitors or ARBs: First-line for left ventricular dysfunction
• Beta-blockers: Once stabilized, start at low doses
• Diuretics: For volume overload
• Aldosterone antagonists: In moderate to severe heart failure
• Digoxin: For symptomatic relief in some cases
• ARNI (sacubitril/valsartan): In chronic heart failure

Arrhythmia Management

• Antiarrhythmic drugs: Based on specific arrhythmia
• Temporary pacing: For complete heart block
• Implantable cardioverter-defibrillator (ICD): For sustained VT/VF
• Catheter ablation: For recurrent arrhythmias

Immunosuppressive Therapy

• Corticosteroids: For giant cell myocarditis, sarcoidosis
• Azathioprine: Combined with steroids in some cases
• Cyclosporine: For refractory autoimmune myocarditis
• Intravenous immunoglobulin (IVIG): Controversial, may help in acute phase

Specific Treatments

• Antiviral therapy: Limited evidence, may help in specific viral causes
• Antibiotics: For bacterial myocarditis (Lyme disease, etc.)
• Antiparasitic drugs: For Chagas disease
• Chelation therapy: For heavy metal toxicity

Advanced Support

• Inotropic support: Dobutamine, milrinone for cardiogenic shock
• Mechanical circulatory support:
  • Intra-aortic balloon pump (IABP)
  • Extracorporeal membrane oxygenation (ECMO)
  • Ventricular assist devices (VAD)
• Heart transplantation: For end-stage heart failure

Follow-up Care

• Serial echocardiography to assess recovery
• Holter monitoring for arrhythmias
• Exercise testing before return to activities
• Long-term heart failure management if needed
• Genetic counseling for familial cases

Prevention

While not all cases of myocarditis can be prevented, several measures can reduce risk:

• Vaccination: Stay up-to-date with recommended vaccines
• Good hygiene: Hand washing, avoid close contact with ill persons
• Safe food practices: Prevent foodborne infections
• Insect protection: In areas with vector-borne diseases
• Avoid illicit drugs: Particularly cocaine and amphetamines
• Limit alcohol: Excessive use can cause toxic myocarditis
• Rest when ill: Avoid strenuous exercise during infections
• Prompt treatment: Of strep throat to prevent rheumatic fever
• Safe sex practices: Reduce risk of HIV and other STIs
• Travel precautions: In areas endemic for Chagas disease
• Monitor medications: Be aware of drugs that can cause myocarditis
• Regular check-ups: For those with autoimmune diseases

When to See a Doctor

Seek medical attention if you experience:

• Sharp chest pain, especially if persistent or worsening
• Palpitations or feeling of skipped heartbeats
• Shortness of breath at rest or with minimal exertion
• Dizziness or lightheadedness
• Swelling in legs, ankles, or feet
• Unusual fatigue or weakness
• Flu-like symptoms followed by cardiac symptoms
• Fainting or near-fainting episodes

Seek emergency care immediately for:

• Severe chest pain or pressure
• Difficulty breathing or gasping for air
• Loss of consciousness
• Rapid or irregular heartbeat with dizziness
• Blue or gray skin color
• Confusion or altered mental status
• Signs of shock (cold, clammy skin, weak pulse)

Related Conditions

Frequently Asked Questions

References

1. Caforio ALP, et al. Current state of knowledge on aetiology, diagnosis, management, and therapy of myocarditis: a position statement of the European Society of Cardiology. Eur Heart J. 2013;34(33):2636-2648.
2. Cooper LT Jr. Myocarditis. N Engl J Med. 2009;360(15):1526-1538.
3. Ammirati E, et al. Management of Acute Myocarditis and Chronic Inflammatory Cardiomyopathy. Circ Heart Fail. 2020;13(11):e007405.
4. Tschöpe C, et al. Myocarditis and inflammatory cardiomyopathy: current evidence and future directions. Nat Rev Cardiol. 2021;18(3):169-193.
5. Law YM, et al. Diagnosis and Management of Myocarditis in Children: A Scientific Statement From the American Heart Association. Circulation. 2021;144(6):e123-e135.