Myocarditis is an inflammation of the heart muscle, known as the myocardium. This condition can weaken the heart, making it harder to pump blood effectively throughout the body. The article will explore how the risk of death from myocarditis varies across different age groups.
Overall Mortality Statistics
While many individuals recover from myocarditis, it can be a life-threatening condition. Some studies report a substantial all-cause mortality rate of 39.3% over a median of 10.1 years in patients with biopsy-proven myocarditis. Other research suggests myocarditis is often mild and temporary. However, severe cases can lead to permanent heart damage, heart failure, or sudden cardiac death.
The mortality rate for acute myocarditis across all ages showed a decline from 1999 to 2019, a trend that reversed during the COVID-19 pandemic. In 2022, a nationwide U.S. analysis reported an overall age-adjusted mortality rate of 1.0 per 1,000,000 population, a decrease from 1.7 in 1999.
Mortality in Pediatric Populations
Death rates from myocarditis in pediatric populations vary, with infants facing a particularly high risk. Mortality rates in newborns have been reported as high as 75%, while estimates for older children range from 10% to 30%. If a child survives the initial acute phase, their chances for long-term survival improve considerably. However, some pediatric patients may develop chronic or recurrent forms of myocarditis.
Myocarditis in children can manifest from mild flu-like illness to a severe, fulminant form that can be fatal. Younger age at presentation, a fulminant presentation with shock, and a severely reduced ejection fraction (below 30%) are factors associated with worse outcomes. Sudden death can be the first indication of the condition. From 1990 to 2021, the global myocarditis-associated mortality rate in children aged 0–14 years decreased from 0.36 to 0.13 per 100,000 population, with children under one year consistently accounting for the highest proportion of deaths.
Mortality in Adult Populations
In adult populations, myocarditis death rates vary by age. A study found that the all-cause mortality rate at 30 days for hospitalized adults aged 20–79 was 6.6%, increasing to 25.6% over 10 years. Within this group, older adults (60–79 years) had a 30-day all-cause mortality rate of 10.0%, compared to 4.7% in young adults (20–39 years) and 4.8% in mid-life adults (40–59 years). While absolute mortality rates increase with age, the long-term impact of acute myocarditis can be particularly severe in young adults, with excess mortality remaining elevated for at least 10 years after initial hospitalization, even in those without complicated phenotypes.
During the COVID-19 pandemic, an increase in acute myocarditis mortality was observed in middle-aged (46–59 years) and older adult (65 years and older) populations. The incidence of cardiovascular death after discharge ranged from 10% to 22%, with the highest rates seen in those requiring mechanical circulatory support. Myocarditis is also implicated in sudden cardiac death among young adults, with rates ranging from 8.6% to 12% in postmortem data.
Contributing Factors to Age-Related Differences
Differences in immune system response contribute to varying myocarditis outcomes across age groups. Developing immune systems in children, especially infants, may react differently to infections, sometimes leading to a more rapid and severe progression of the disease. Conversely, the aging immune system in older adults can be less effective at resolving inflammation, potentially leading to more persistent or severe myocardial damage. This altered immune function can influence the body’s ability to clear viral infections that often trigger myocarditis.
Underlying health conditions also play a role in age-related mortality differences. Older adults frequently have comorbidities such as hypertension, diabetes, and pre-existing heart conditions, which can exacerbate the effects of myocarditis and increase the risk of complications like heart failure or arrhythmias. In younger adults, particularly athletes, myocarditis is a recognized cause of sudden cardiac death, sometimes occurring during or immediately after exercise. This suggests that even in seemingly healthy individuals, certain underlying predispositions or the specific nature of the inflammatory response can lead to severe outcomes.
The etiology or causes of myocarditis can also differ by age, influencing disease severity and mortality. While viral infections are common triggers across all ages, specific viruses may have varying impacts depending on the host’s age and immune status, potentially causing more severe inflammation in particular age groups. The clinical presentation and subsequent diagnosis can also be delayed in some age groups, particularly in infants and the elderly, due to non-specific symptoms. Delayed diagnosis can postpone appropriate treatment, potentially leading to worse outcomes and higher mortality rates.