Purpose To study clinical features of myocarditis and its possible mechanisms (including persistence of SARS-Cov-2 in the myocardium) in the long-term period after acute COVID-19. Methods Fifteen patients (8 male and 7 female, mean age 47.8±13.4, 24–65 years) diagnosed with postcovid myocarditis were included in the study. The diagnosis of COVID-19 was confirmed by positive PCR results in 40%, and seroconversion in all patients. The average time of admission after COVID-19 was 4 [3; 7] months, from 2 to 9 months. The diagnosis of myocarditis was confirmed by cardiac MRI in 10 patients and by right ventricular endomyocardial biopsy (EMB) in 6 patients. The PCR for cardiotropic viruses and PCR with immunohistochemical study for SARS-Cov2 detection were used. All patients had study for anti-heart antibodies (AHA), EchoCG, and Holter ECG. Coronary atherosclerosis was excluded in all patients over 40 years (7 coronary angiography, 4 cardiac CT). Results A clear association of the cardiac symptoms with a previous new coronavirus infection was noted in all patients. The symptoms started 1–5 months following COVID-19. MRI showed subepicardial and intramyocardial LGE, signs of hyperemia, increased T1 relaxation time, edema. AHA levels were increased 3–4-fold in 73%. Two variants of postcovid myocarditis were observed. 1. Arrhythmic variant (n=6) – newly developed frequent supraventricular or ventricular extrasystole, recurrent atrial fibrillation in the absence of systolic dysfunction. 2. Decompensated variant with biventricular heart failure (n=9): the mean LV EF was 34.1±7.8% (23 to 46%), LV EDD 5.8±0.7 cm, EDV 153.8±46.1 ml, pulmonary artery systolic pressure 40.7±11.2 mmHg. In one case, myocarditis was accompanied by IgG4- and ANCA-negative aortitis. SARS-Cov-2 RNA was detected in 4 of 5 myocardial biopsies (in one case the material in the study). The longest period of virus persistence after COVID-19 was 9 months. By using spike and nucleocapsid antibodies, coronavirus was detected in cardiomycytes and macrophages. Data of patients with morphologically proved myocarditis are presented in Table 1. Lymphocytic myocarditis was diagnosed and confirmed immunohistochemically (n=5); giant cell myocarditis with atrial standstill was detected in one more case (Fig. 1). Three patients had also signs of endocarditis, in two cases with parietal thrombosis. Conclusions COVID-19 can lead to the subacute and chronic myocarditis of varying severity. Post-COVID myocarditis manifests itself in two main clinical forms - isolated arrhythmias and systolic dysfunction with heart failure. Post-COVID myocarditis is characterized by prolonged persistence of coronavirus (up to 9 months in this study, in most patients with decompensated variant) in combination with high immune activity (high titers of AHA), which should be considered as the main mechanisms of its long-term course. Treatment approaches for such myocarditis require investigation. FUNDunding Acknowledgement Type of funding sources: None. Table 1. Patients with EMB proved myocarditis Figure 1. The EMB in postcovide myocarditis

Aim    To study clinical features of myoendocarditis and its possible mechanisms, including persistence of SARS-Cov-2 in the myocardium, in the long-term period following COVID-19.Material and methods    This cohort, prospective study included 15 patients aged 47.8±13.4 years (8 men) with post-COVID myocarditis. The COVID-19 diagnosis was confirmed for all patients. Median time to seeking medical care after COVID-19 was 4 [3; 7] months. The diagnosis of myocarditis was confirmed by magnetic resonance imaging (MRI) of the heart (n=10) and by endomyocardial biopsy of the right ventricle (n=6). The virus was detected in the myocardium with PCR; immunohistochemical (IHC) study with antibody to SARS-Cov-2 was performed; anticardiac antibody level was measured; and echocardiography and Holter monitoring were performed. Hemodynamically significant coronary atherosclerosis was excluded for all patients older than 40 years.Results    All patients showed a clear connection between the emergence or exacerbation of cardiac symptoms and COVID-19. 11 patients did not have any signs of heart disease before COVID-19; 4 patients had previously had moderate arrhythmia or heart failure (HF) without myocarditis. Symptoms of myocarditis emerged at 1–5 months following COVID-19. MRI revealed typical late gadolinium accumulation, signs of hyperemia, and one case of edema. The level of anticardiac antibodies was increased 3-4 times in 73 % больных. Two major clinical variants of post-COVID myocarditis were observed. 1. Arrhythmic (n=6), with newly developed extrasystole or atrial fibrillation without systolic dysfunction. 2. Decompensated variant with systolic dysfunction and biventricular HF (n=9). Mean left ventricular ejection fraction was 34.1±7.8 %, and left ventricular end-diastolic dimension was 5.8±0.7 cm. In one case, myocarditis was associated with signs of IgG4‑negative aortitis. SARS-Cov-2 RNA was found in 5 of 6 biopsy samples of the myocardium. The longest duration of SARS-Cov-2 persistence in the myocardium was 9 months following COVID-19. By using antibody to the Spike antigen and nucleocapsid, SARS-Cov-2 was detected in cardiomyocytes, endothelium, and macrophages. Five patients were diagnosed with lymphocytic myocarditis; one with giant-cell myocarditis; three patients had signs of endocarditis (infectious, lymphocytic with mural thrombosis).Conclusion    Subacute/chronic post-COVID myocarditis with isolated arrhythmias or systolic dysfunction is characterized by long-term (up to 9 months) persistence of SARS-Cov-2 in the myocardium in combination with a high immune activity. Endocarditis can manifest either as infectious or as nonbacterial thromboendocarditis. A possibility of using corticosteroids and anticoagulants in the treatment of post-COVID myoendocarditis should be studied.

Giant cell myocarditis (GCM) is a rare condition. Its association with SARS‐CoV‐2 has not been described before. The 46‐year‐old female patient was admitted to the clinic on September 2020. She had 7 year adrenal insufficiency history and infarct‐like debut of myocardial disease in November 2019. After COVID‐19 in April 2020, cardiac disease progressed. The examination showed low QRS voltage, QS complexes in V 1 –V 5 leads, atrial standstill, left ventricular systolic and restrictive dysfunction, elevated anti‐heart antibodies, and subepicardial late gadolinium enhancement by magnetic resonance imaging. Endomyocardial biopsy and pacemaker implantation were performed, but the patient died suddenly due to ventricular tachycardia or ventricular fibrillation (the resuscitation was ineffective). The autopsy revealed GCM, SARS‐CoV‐2, and Parvovirus B19 were detected in the myocardium. The role of SARS‐CoV‐2 in the pathogenesis of autoimmune myocarditis is discussed.

Introduction: Commonly accepted clinical classification of arrhythmogenic right ventricular cardiomyopathy (ARVC) is still not developed. Objective: To study the clinical forms of ARVC. Methods: Fifty-four patients (38.7 ± 14.1 years, 42.6% men) with ARVC. Follow-up period: 21 (6-60) months. All patients underwent electrocardiography, 24 h-Holter monitoring, echocardiography, and DNA diagnostic. Magnetic resonance imaging was performed in 49 patients. Results: According to the features of clinical course of ARVC, 4 clinical forms were identified. (I) Latent arrhythmic form (n = 27)-frequent premature ventricular contractions and/or nonsustained ventricular tachycardia (VT) in the absence of sustained VT and syncope; characterized by absence of fatal arrhythmic events. (II) Manifested arrhythmic form (n = 11)-sustained VT/ventricular fibrillation; the high incidence of appropriate implantation of cardioverter-defibrillator (ICD) interventions (75%) registered. (III) ARVC with progressive chronic heart failure (CHF, n = 8) as the main manifestation of the disease; incidence of appropriate ICD interventions was 50%, mortality rate due to CHF was 25%. (IV) Combination of ARVC with left ventricular noncompaction (n = 8); characterized by mutations in desmosomal or sarcomere genes, aggressive ventricular arrhythmias, appropriate ICD interventions in 100% patients. Described 4 clinical forms are stable in time, do not transform into each other, and they are genetically determined. Conclusions: The described clinical forms of ARVC are determined by a combination of genetic and environmental factors and do not transform into each other. The proposed classification could be used in clinical practice to determine the range of diagnostic and therapeutic measures and to assess the prognosis of the disease in a particular patient.

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