Overview 

Cardiomyopathy refers to a disease of the muscle of the heart. In children, this is most often a heterogeneous condition (with multiple causes) characterised by structural or functional abnormalities of the heart muscle not explained by other cardiac diseases for instance, congenital heart defects.¹ Among the diverse etiologies, viral infections are an important and well-recognised contributor, especially in cases of myocarditis and dilated cardiomyopathy (DCM). Understanding how viral infections lead to cardiomyopathy, including which viruses are involved, the evidence supporting this relationship, the clinical course, risk factors, and therapeutic implications, is crucial for clinicians, researchers, and families. 

This article will explore these areas through risk factors, mechanisms of disease, diagnosis and treatment.

What is viral cardiomyopathy?

Viral cardiomyopathy refers to a spectrum of diseases in which a virus causes damage, directly or via immune‐mediated mechanisms, to the myocardium (heart muscle). This may initially present as myocarditis (inflammation) and can progress to a long‐term cardiomyopathy (commonly DCM) with impaired ventricular function, dilation, and often risk of heart failure, arrhythmia, or even a need for transplantation.² 

Myocardial injury can arise from an acute infection, a persistent infection, or the triggering of (auto)immune responses that persist even after viral clearance or latent persistence.

Mechanisms: how viruses cause myocardial injury and cardiomyopathy 

Viral-induced myocardial injury is a complex, multi-step process involving several interlinked pathophysiological mechanisms that contribute not only to acute myocarditis but also to long-term cardiac remodeling - changes to the structure of the heart - and dilated cardiomyopathy; understanding these mechanisms is essential for guiding both diagnosis and potential therapeutic approaches.

Direct viral injury

Many cardiotropic viruses (affecting the heart) can infect myocytes, the muscle cells of the heart walls, or cardiac endothelial cells. The virus may replicate, cause cytopathic effects, including cell death or the disruption of cell structure. For instance, enteroviruses and adenoviruses can directly injure myocardium.³

Immune activation and inflammation

After infection, the innate immune response and later adaptive immune response are engaged. Infiltration of immune cells, including cytokines, chemokines, and white blood cells (neutrophils, monocytes, macrophages, T‑cells) occurs. This inflammatory response may aim to clear the virus but can lead to collateral damage of the myocardium.⁵ If inflammation is severe or prolonged, remodeling, fibrosis, and loss of contractile tissue may occur, resulting in impaired contraction of the heart.³

Viral persistence or latency

Some viruses may persist in cardiac tissue (endomyocardial biopsies detect viral genomes), possibly in latent form. Persistent viral infections (or viral components) may sustain low‐grade inflammation or affect cellular function (e.g., via mitochondrial dysfunction) even after the first, strongest, acute phase of the infection. Whether presence of a virus upon testing implies causation or not remains debated and case-by-case treatment is required.⁴

Autoimmune or auto‐reactive responses

Viral infection sometimes triggers autoantibodies or molecular mimicry: immune responses initially directed at viral antigens cross‐react with the patient’s own myocardial proteins. This can sustain myocardial injury even after the virus is no longer replicating. Genetic predisposition, HLA types, and immune regulation likely modulate risk of this occuring.⁵

Remodeling and fibrosis

After injury, cardiac remodeling takes place. If damage is extensive or repair is imperfect, ventricular dilation (widening), wall thinning, fibrosis (scarring), and compromised contractility may persist or worsen over time, leading to dilated cardiomyopathy (DCM) phenotype.³ 

Viruses implicated

Several viruses have been identified in pediatric myocarditis/cardiomyopathy. Some are more common or more studied than others.

Epidemiology: how often viruses lead to cardiomyopathy in children 

Pediatric myocarditis, particularly of viral or infectious origin, is a leading cause of acquired heart failure in children, and a substantial portion of new-onset dilated cardiomyopathy (idiopathic or of unknown origin) is retrospectively linked to prior viral myocarditis. In some registries, myocarditis accounts for 30-35% of pediatric cases presenting with a DCM phenotype.⁸ Viral genomes have been identified in approximately 30-40% of endomyocardial biopsies from children with DCM or acute heart failure across multiple studies.⁹ Younger children, especially infants and toddlers, appear more susceptible to severe disease, likely due to immature immune regulation or being exposed to primary infections; human herpesvirus-6 (HHV‑6) is particularly common in those under three years of age.

Clinical course and outcomes

The natural history following viral myocarditis in children is highly variable, while some recover fully, others experience persistent cardiac dysfunction, and a subset progress to experience heart failure, require transplantation, or even reach the point of mortality. 

Many children with acute viral myocarditis show improvement within weeks to months, particularly if myocardial damage is limited and supportive care is initiated early. In one study of 63 children with acute heart failure, viral genomes were detected in 35%, and those with virus-positive biopsies, especially with parvovirus B19, demonstrated better recovery of ejection fraction and more favorable long-term outcomes compared to virus-negative cases.⁶ 

A proportion of children go on to develop chronic dilated cardiomyopathy. This is characterised by ongoing systolic dysfunction (inadequate pumping of the heart), ventricular dilation, and increased risk of complications such as arrhythmias, thromboembolism, or the need for heart transplantation. Mortality remains significant: in severe or fulminant (sudden and severe) myocarditis, reported pediatric mortality rates can reach up to ~25%, with many survivors requiring long-term monitoring due to residual dysfunction.¹⁰

Risk modifiers and prognostic factors

Which children are more likely to progress to cardiomyopathy or have worse outcomes depends on a number of factors: 

• Extent of initial injury: more severe inflammation; greater myocyte necrosis; fulminant myocarditis presentation
• Viral type and load/activity: active infection (as opposed to latent presence) seems more damaging. High viral load or replicative virus also correlates with worse outcomes. Studies are ongoing to differentiate between the effects of specific viruses
• Persistent viral presence: failure to clear virus or sustained low‑grade infection may contribute to chronic myocardial damage
• Age: younger age, especially infants or toddlers, tends to carry worse prognosis 
• Timeliness of diagnosis and supportive care: delay in recognising myocarditis, delays in hospital care, inotropic support, mechanical support, etc., may worsen disease 
• Degree of ventricular dysfunction at presentation: more severe dilation, lower ejection fraction, and more hemodynamic instability lead to a worse long‑term outcome 

Diagnostic considerations 

Detecting viral involvement in pediatric cardiomyopathy entails:

• History: preceding viral illness (respiratory, gastrointestinal), timing in relation to symptoms of heart failure
• Lab tests: viral serology, polymerase chain reaction (PCR) on blood or biopsy, viral RNA/DNA detection
• Imaging: echocardiography for ventricular function and dilation; cardiac magnetic resonance imaging (CMR) for myocardial edema, including specific techniques like late gadolinium enhancement (LGE), showing fibrosis 
• Endomyocardial biopsy(EMB): gold standard for detecting viral genomes in myocardium, inflammatory cell infiltrates, and necrosis. However, biopsy is highly invasive and hence used selectively

Therapeutic implications

Knowing that viral infection plays a role in pediatric cardiomyopathy suggests some possible interventions and management strategies:

• Supportive care: treating heart failure, stabilising hemodynamics, managing arrhythmias, ensuring adequate perfusion. Early ICU care if needed
• Antiviral or immunomodulatory therapy: The evidence is mixed. Some trials in adults showed the benefit of immunosuppression in DCM when inflammation is present, and virus is non‐detectable; in children, immunoglobulins (IVIG) are sometimes used. Antiviral therapy is more challenging, often virus‐specific, and efficacy depends on early intervention
• Close monitoring: For children with viral myocarditis, even after apparent recovery, long‑term follow-up is needed for ventricular function, possibility of late dilation or dysfunction
• Mechanical circulatory support/transplantation: For those who experience acute decompensated heart failure (ADHF), advanced, more drastic and invasive therapies may be required

Uncertainties and research gaps

The detection of viral genomes in myocardial tissue does not necessarily confirm causality, as differentiating between latent, low-level viral presence and active, pathogenic infection remains a significant challenge. Currently, there is no consensus on viral load thresholds in cardiac tissue or which specific viruses are most predictive of adverse outcomes. A major limitation in the field is the lack of large, randomized clinical trials in pediatric populations evaluating the efficacy of antiviral or immunomodulatory therapies. Additionally, geographic variation in virus prevalence complicates generalisation, as different regions may have distinct dominant cardiotropic viruses. Long-term follow-up data, particularly into adolescence and adulthood, are sparse, leaving uncertainties around the chronic trajectory and outcomes of virus-associated cardiomyopathy in children.

FAQs

Does every child with a viral infection risk developing cardiomyopathy?

No. Most children with viral infections do not develop myocarditis or cardiomyopathy. It depends on several factors like the type of virus, whether the infection reaches the cardiac tissue, the immune response, genetic predisposition, and how severe or prolonged the infection is.

Which viruses are most dangerous in this regard?

Enteroviruses, adenoviruses, parvovirus B19, and HHV‑6 are among the more commonly implicated in leading to cardiomyopathy. Furthermore, there is emerging recognition of SARS‑CoV‑2 (COVID‑19) related myocarditis as well. Disease severity tends to vary; for example, HHV‑6 in young children may have more severe outcomes.

Are there preventative measures?

Generally, preventing viral infections (vaccination where available, hygiene), prompt treatment of viral illnesses, and monitoring symptoms closely are all helpful preventative measures. In known cardiotropic virus outbreaks, awareness for cardiac symptoms helps, but unfortunately, there is no specific, widely established prophylactic antiviral therapy for children at risk.

Summary

Viral infections are a well-established cause of myocarditis in children and represent a major pathway toward the development of dilated cardiomyopathy (DCM). A variety of viruses have been implicated, including enteroviruses, adenoviruses, parvovirus B19, human herpesvirus 6, influenza, and more recently, SARS-CoV-2. The underlying mechanisms of myocardial injury include direct viral cytotoxicity, immune-mediated inflammation, persistent viral presence or latent infection, autoimmune responses, and subsequent cardiac remodeling or fibrosis. Epidemiologically, a significant proportion of new-onset pediatric DCM cases may be attributed to prior viral myocarditis, with younger children generally at higher risk for severe disease. Clinical outcomes vary widely; while some children fully recover, others develop chronic cardiac dysfunction, require heart transplantation, or experience adverse outcomes. Prognosis depends on factors such as the specific viral pathogen, severity of initial injury, timing of medical intervention, and overall host response. Diagnosis typically involves clinical history, imaging modalities such as echocardiography and cardiac MRI, endomyocardial biopsy, and viral detection through PCR or serology. Current treatment remains primarily supportive, although antiviral and immunomodulatory therapies show potential and are under ongoing investigation.