The aim – to study the influence of clinical and anamnestic characteristics, namely: arterial hypertension, coronary heart disease, diabetes, previous myocardial infarction, acute cerebrovascular accident, metabolic cardiomyopathy, of myocarditis in the anamnesis and chronic heart failure on the development of atrial fibrillation (AF) de novo or the deterioration of the course of an already existing arrhythmia in patients after suffering a coronavirus infection (CI).Materials and methods. The study involved 116 patients with AF who were hospitalized in the department of clinical arrhythmology and electrophysiology from September 20.09.2020 to 21.12.2021 and had a history of coronavirus infection (CI). The 1st group – 36 people (31 %) in whom AF occurred after CI. The 2nd group – 25 patients in whom the form of AF has changed. The 3rd group – 55 patients in whom the form of AF did not change. In the 3rd group, two subgroups were formed: 3A – 35 patients in whom, although the form of AF did not change, the frequency or duration of arrhythmia paroxysms increased, and 3B – 20 patients without significant changes in the course of AF. As the first control group (C1), 49 patients with AF without a history of CI were examined. The second control group (C2) was formed by 22 patients after a CI in whom AF did not develop.Results and discussion. In patients of the 1st group, hypertension occurred 1.4 times more often (p<0.001) than in the subjects of the 2С comparison group. The presence of hypertension, especially of the 3rd stage, increased the probability of the appearance of AF after a previous CI, which probably contributed to the emergence of a new, more serious form of AF and worsened the course of this arrhythmia. CHD was probably more common in patients of group 2, compared to group 3. Coronary heart disease was also statistically more frequent in patients of subgroup 3A – in patients in whom the form of AF did not change, but the course of the arrhythmia worsened – the frequency and duration of paroxysms increased, in contrast to the subgroup 3B, in whose patients the course of AF did not fundamentally change. In patients with AF who underwent CI and had a history of аcute violation of cerebral circulation, its course worsened, compared to group 3B, in which the course of this arrhythmia did not change (p<0.001). Myocarditis in the anamnesis was probably much more common in patients of the 1st group, in comparison with the C2 group. There was a significant difference between the frequency of myocarditis in the anamnesis in patients of the 2nd group, in which the form of AF after CI changed to a more severe one, and in the patients of the 3rd group, in which the form of this arrhythmia did not change. Diabetes significantly and reliably affected the deterioration of the course of AF in patients who had this arrhythmia before CI, and contributed to a change in the form of AF to a more unpleasant one (2nd group) in comparison with patients without a change in the form of this arrhythmia (3rd group). Metabolic cardiomyopathy was reliably significantly more common in patients of the 1st group compared to the C2 group. There is a big difference between the frequency of metabolic cardiomyopathy in patients of the 2nd group in comparison with the patients of the 3rd group. In the patients of the 2nd group, in whom the form of AF changed to a more threatening one. There were statistically more people with heart failure IIA, and a higher stage of HF in the digital form in equal to persons of the 3rd group, which included patients in whom the form of AF did not change.Conclusions. In patients with atrial fibrillation who suffered a coronavirus infection, the most common concomitant diseases were found to be: HF I–IIA stage – 92 % (in more than half of the cases – in 51.4 % it was HF IIA stage), arterial hypertension – 83 %, coronary heart disease – 60 %, myocarditis – 28 %, diabetes was recorded in 12 % of patients. Arterial hypertension, especially of the 3rd stage, myocarditis in the anamnesis, heart failure of the II A stage caused the appearance of paroxysms of AF de novo after the transferred coronavirus infection in the cohort of patients studied by us. The aforementioned factors, as well as ischemic heart disease, myocardial infarction, and acute cerebrovascular accident in the anamnesis, have been established as markers of the transformation of the paroxysmal form of atrial fibrillation into persistent, or persistent atrial fibrillation into a permanent form of this arrhythmia after being infected with COVID-19.