Acute myocarditis linked to higher 90-day all-cause mortality and adverse cardiac outcomes

Acute myocarditis is associated with a high 90-day all-cause mortality and adverse cardiac outcomes including arrhythmias and cardiac arrest.

Patients hospitalised with acute myocarditis (MC) are at an increased risk of all-cause mortality, heart failure, arrhythmias and cardiac arrest compared to matched controls, according to research by a group from the Department of Cardiology, Aalborg University Hospital, Denmark. Inflammation of the cardiac muscle or myocardium (myocarditis) is typically seen in infants and teenagers but can occur at any age. Acute MC symptoms include a stabbing pain and or tightness in the chest which may spread across the body, shortness of breath with light exercise, difficulty in breathing at rest and even flu-like symptoms such as a high temperature, tiredness and fatigue. In addition, acute myocarditis has been shown to be a frequent cause of sudden death in men aged 18 to 28 years of age and in high school athletes. Although evidence points to favourable long-term outcomes in adults with myocarditis, the condition does appear to be associated with an increased risk of  cardiovascular and all-cause mortality within 3 months after discharge.

However, there is limited data on the short-term risks of MC, leading the Danish group to retrospectively analysis the outcomes for patients hospitalised with the condition. The researchers turned to the Danish Civil Registration System, which contains information on all registered Danish citizens and can be linked to other administrative databases. Patients were included in the analysis if they had been hospitalised with a primary diagnosis of MC between 2002 and 2018 or as a secondary diagnosis and with a primary diagnosis of heart failure (HF), ventricular tachycardia (VT), ventricular fibrillation (VF), cardiac arrest and cardioverter-defbrillator (ICD). These secondary diagnoses were used because the clinical diagnosis of MC may involve one of these other conditions. Those with myocarditis was age and sex-matched to a population of control patients without a diagnosis of prior MC in a 1:5 ratio. The primary outcome of interest was 90-day all-cause mortality and secondary outcomes were included 90-day presumed cardiovascular causes of death and 90-day risks for HF, a composite of VT or VF or cardiac arrest and ICD. The analysis involved regression modelling with hazard ratios adjusted for age, sex and co-morbidities.

Findings

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A total of 15,138 patients were included in the analysis with 2523 with myocarditis who had a median age of 48 years (67.7% male). The 90-day all-cause mortality risk was 4.9% for those with myocarditis versus 0.3% for controls (p < 0.001), with an adjusted hazard ratio, aHR of 22.12 (95% CI 14.44 – 33.88). Similarly, the 90-day risk for  HF was 75 times higher (aHR = 75.29, 95% CI 42.54 – 133.23, p < 0.001), as was the risk for the VT/VF composite (aHR = 78.80, p < 0.01) and for ICD implantation (aHR = 65.56, p < 0.01).

Commenting on these results, the authors suggested the myocarditis is a serious disease that is associated with a significantly elevated short-term risk of death. They concluded that “patients with acute myocarditis may benefit from careful diagnostic work-up including cardiac monitoring in the early phase after diagnosis.”

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