Outcome and Morphofunctional Changes on Cardiac Magnetic Resonance in Patients With Acute Myocarditis Following mRNA COVID-19 Vaccination

Fulminant Myocarditis Temporally Associated with COVID-19 Vaccination

PURPOSE OF REVIEW

Coronavirus disease-2019 (COVID-19) vaccines have been related to rare cases of acute myocarditis, occurring between 1 in 10,000 and 1 in 100,000 individuals, approximately. Incidence of COVID-19 vaccine-associated myocarditis varies with age, sex, and type of vaccine. Although most patients with acute myocarditis temporally associated with COVID-19 vaccines have an uneventful course, a small subpopulation presents with cardiogenic shock (termed fulminant myocarditis [FM]). This review explored the prevalence, clinical presentation, management, and prognosis of COVID-19 vaccine-associated acute myocarditis, specifically focusing on FM and comparing patients with fulminant versus non-fulminant myocarditis.

RECENT FINDINGS

Cases of FM represent about 2-4% (0 to 7.5%) of COVID-19 vaccine-associated acute myocarditis cases, and mortality is around 1%, ranging between 0 and 4.4%. First, we identified 40 cases of FM up to February 2023 with sufficient granular data from case reports and case series of COVID-19 vaccine-associated acute myocarditis that occurred within 30 days from the last vaccine injection. This population was compared with 294 cases of non-fulminant acute myocarditis identified in the literature during a similar time. Patients with FM were older (48 vs. 27 years), had a larger proportion of women (58% vs. 9%), and mainly occurred after the first shot compared with non-fulminant cases (58% vs. 16%). The reported mortality was 27% (11 out of 40), in line with non-vaccine-associated fulminant myocarditis. These data were in agreement with 36 cases of FM from a large Korean registry. Herein, we reviewed the clinical features, imaging results, and histological findings of COVID-19 vaccine-associated fulminant myocarditis. In conclusion, COVID-19 vaccine-associated FM differs from non-fulminant forms, suggesting potential specific mechanisms in these rare and severe forms. Mortality in vaccine-associated FM remains high, in line with other forms of FM.

Myocarditis and Chronic Inflammatory Cardiomyopathy, from Acute Inflammation to Chronic Inflammatory Damage: An Update on Pathophysiology and Diagnosis

Acute myocarditis covers a wide spectrum of clinical presentations, from uncomplicated myocarditis to severe forms complicated by hemodynamic instability and ventricular arrhythmias; however, all these forms are characterized by acute myocardial inflammation. The term "chronic inflammatory cardiomyopathy" describes a persistent/chronic inflammatory condition with a clinical phenotype of dilated and/or hypokinetic cardiomyopathy associated with symptoms of heart failure and increased risk for arrhythmias. A continuum can be identified between these two conditions. The importance of early diagnosis has grown markedly in the contemporary era with various diagnostic tools available. While cardiac magnetic resonance (CMR) is valid for diagnosis and follow-up, endomyocardial biopsy (EMB) should be considered as a first-line diagnostic modality in all unexplained acute cardiomyopathies complicated by hemodynamic instability and ventricular arrhythmias, considering the local expertise. Genetic counseling should be recommended in those cases where a genotype-phenotype association is suspected, as this has significant implications for patients' and their family members' prognoses. Recognition of the pathophysiological pathway and clinical "red flags" and an early diagnosis may help us understand mechanisms of progression, tailor long-term preventive and therapeutic strategies for this complex disease, and ultimately improve clinical outcomes.

Myocarditis: Etiology, Pathogenesis, and Their Implications in Clinical Practice

Myocarditis is an inflammatory disease of the myocardium caused by infectious or non-infectious agents. It can lead to serious short-term and long-term sequalae, such as sudden cardiac death or dilated cardiomyopathy. Due to its heterogenous clinical presentation and disease course, challenging diagnosis and limited evidence for prognostic stratification, myocarditis poses a great challenge to clinicians. As it stands, the pathogenesis and etiology of myocarditis is only partially understood. Moreover, the impact of certain clinical features on risk assessment, patient outcomes and treatment options is not entirely clear. Such data, however, are essential in order to personalize patient care and implement novel therapeutic strategies. In this review, we discuss the possible etiologies of myocarditis, outline the key processes governing its pathogenesis and summarize best available evidence regarding patient outcomes and state-of-the-art therapeutic approaches.