You are presented with a paragraph from a COVID-19 literature. Classify the topics of this piece of text by choosing from the following categories:

- Epidemic Forecasting: The content relates to predictions about the spread of COVID-19.
- Treatment: The paragraph discusses therapeutic methods or medication for COVID-19.
- Prevention: The content covers measures to prevent the spread of COVID-19.
- Mechanism: The paragraph explains the biological mechanisms of the virus.
- Case Report: The content is a report of a COVID-19 case.
- Transmission: The paragraph discusses how COVID-19 is transmitted.
- Diagnosis: The content is about diagnosing COVID-19 in individuals.

Your classification should be provided as an element within a JSON array. The array should be formatted with topics enclosed in double quotes and separated by commas, following the JSON format, for example: ["Topic1", "Topic2", ...]. Include all applicable topics within the array. Your output should be a valid JSON array, and no additional text should be included in your response.

Article:

BACKGROUND: During the COVID-19 pandemic, the number of admissions to the emergency department (ED) due to a primary diagnosis of atrial fibrillation (AF) has decreased when compared to pre-pandemic times. The principal aim of the study was to assess the frequency of SARS-CoV-2 infections and sinus rhythm restoration among patients who arrived at the ED with AF. Secondary aims included determining whether patients arriving at the ED principally due to AF delayed their presentations and whether the frequency of successful cardioversion for AF was decreased during the pandemic period. MATERIALS AND METHODS: A retrospective analysis of medical records of patients admitted to two hospital EDs due to AF during July-December 2019 (pre-pandemic period) versus July-December 2020 (pandemic period) was performed. RESULTS: During the study periods, 601 ED visits by 497 patients were made due to the primary diagnosis of AF. The patients were aged 71.2+/-13.5 years and 51.3% were male. The duration of an AF episode before the ED admission was 10 h (4.5-30 h) during the pandemic period vs. 5 h (3-24 h) during the non-pandemic period (p = 0.001). A shorter duration of the AF episode before ED admission was associated with the successful restoration of the sinus rhythm. During the pandemic period, among patients with short-lasting AF who were not treated with Phenazolinum, the restoration of the sinus rhythm was more frequent in the Copernicus Memorial Hospital than in the University Hospital (p = 0.026). A positive SARS-CoV-2 test was found in 5 (1%) patients, while 2 other patients (0.5%) had a prior diagnosis of COVID-19 disease noted in their medical history. CONCLUSIONS: 1. The number of AF episodes treated in these two EDs was lower during the pandemic than non-pandemic period. 2. The patients with AF appeared at the ED later after AF onset in the pandemic period. 3. Successful cardioversion of atrial fibrillation was more frequent during the pre-pandemic period in one of the two hospitals. 4. A difference of approaches to the treatment of short-lasting AF episodes between EDs during the pandemic period may exist between these two EDs. 5. The patients with SARS-CoV-2 infection during the second wave of the COVID-19 pandemic constituted a small percentage of the patients admitted to EDs due to an AF episode.
["Prevention"]