Risk Factors for Myocarditis in Adolescents
In an adolescent presenting with acute chest pain and first-degree AV block, the primary risk factors to consider are recent viral infection (particularly enteroviruses, adenovirus, parvovirus B19, Coxsackievirus, influenza, and coronavirus), male sex, and young age, with viral etiologies accounting for the vast majority of myocarditis cases in this population. 1, 2
Infectious Risk Factors
Viral infections are the predominant cause of myocarditis in adolescents:
- Enteroviruses, adenovirus, and parvovirus B19 are the most common viral causes in pediatric and adolescent populations 1
- Coxsackievirus B is a well-documented cause of myocarditis presenting with acute chest pain in adolescents 3, 4
- Influenza and coronavirus (including COVID-19) are important viral triggers 2
- Mycoplasma pneumoniae can cause myocarditis with severe chest pain and distinct ECG findings in adolescents 5
- Bacterial, fungal, protozoal, spirochete, and rickettsial infections are less common but possible causes 6
Demographic Risk Factors
- Male sex is associated with higher risk, particularly for fulminant presentations with viral myocarditis 1
- Young age itself is a risk factor, with adolescents being a vulnerable population 1
- Younger patients (<1 year) have worse outcomes than older children and adolescents 1
Non-Infectious Risk Factors
Toxic and immune-mediated causes to consider:
- Drugs and medications, including immune checkpoint inhibitors 2
- Vaccines, including smallpox and mRNA COVID-19 vaccines 2
- Systemic autoimmune disorders such as systemic lupus erythematosus, rheumatoid arthritis, and systemic sclerosis 6, 2
- Radiation, chemicals, and other physical agents can lead to cardiac inflammation 6
Clinical Presentation Patterns Suggesting Higher Risk
The presence of certain clinical features indicates higher risk for complications:
- Conduction abnormalities (including first-degree AV block as in your patient) can progress to complete heart block and trigger ventricular arrhythmias 6, 7
- Progressive wall motion abnormalities with deteriorating LV function on echocardiography 6, 7
- Persistent or fluctuating cardiac troponin concentrations 6, 7
- Widening of the QRS complex 6, 7
- Frequent non-sustained ventricular arrhythmias may precede sustained life-threatening arrhythmias 6, 7
High-Risk Myocarditis Subtypes
Certain forms carry particularly poor prognosis:
- Giant cell myocarditis typically affects young individuals and is usually fatal if untreated, requiring endomyocardial biopsy for diagnosis 6
- Fulminant myocarditis presents with severe acute heart failure and refractory ventricular tachyarrhythmias, with only 58% short-term survival 6, 7, 8
- Cardiac sarcoidosis may present acutely similar to myocarditis 6
Geographic and Endemic Risk Factors
- Lyme disease (Borrelia burgdorferi) affects 0.3-8% of infected individuals and frequently causes AV conduction abnormalities 6
- Chagas disease (Trypanosoma cruzi) is endemic in Central and South America, affecting 13% of the population at risk 6
- HIV/AIDS can cause cardiac involvement and myocarditis 6
Critical Pitfall to Avoid
Ventricular tachycardia is the most common sustained arrhythmia in pediatric myocarditis, occurring in 76% of 314 cases with arrhythmias, and patients with sustained arrhythmias have a very high risk of cardiac arrest (OR 5.4,95% CI 3.9-7.4, P<0.001) compared to those without arrhythmias. 6, 7 This underscores the importance of continuous ECG monitoring in adolescents with suspected myocarditis and any conduction abnormality, including first-degree AV block.
Immediate Management Implications for Your Patient
Given the presentation of acute chest pain with first-degree AV block in an adolescent:
- Mandatory hospitalization with prolonged ECG monitoring is required, as AV block can progress and trigger ventricular tachyarrhythmias 6, 7
- Obtain detailed history of recent viral illness (flu-like symptoms, upper respiratory infection, gastrointestinal symptoms) 1, 3, 5
- Assess for systemic autoimmune conditions and medication/vaccine exposure 6, 2
- Temporary pacemaker insertion is indicated if symptomatic heart block develops 6, 7, 8