Today, while there is a global fight against the COVID-19 pandemic, there is an ongoing debate on the effects of the disease on myocarditis. Furthermore, some COVID-19 vaccines have been associated with the development of myocarditis. Diaz et al. associated myocarditis with some vaccines, including MRNA vaccines [17]. The Center for Disease Control and Prevention recently declared a possible association between COVID-19 mRNA vaccines and myocarditis, especially in young patients with an incidence of 4.8 per 1 million cases [18]. Some studies have reported that there is no definitive scientific evidence on this association, and postvaccination adverse effects are known to be benign and self-limited [3], while others suggested that myocarditis is one of the complications that manifest following COVID-19 infection [18, 19]. The potential benefit of global vaccine campaigns against COVID-19 is much more greater than self-limited myocarditis. However, especially, speculative news on media, social platforms and the Internet pose a risk of misleading people who hesitate to being vaccinated and contribute to the infodemic, which is defined as “the dangers of misinformation phenomena during the management of an outbreak [21]. As a result, these news and grapevine lead people to increasingly seek answers for their health-related problems on the Internet, and particularly YouTube.

YouTube is the most commonly used video-sharing website worldwide. Any individual is allowed to upload videos at free cost after registration. YouTube has become a great social media platform and a generous source of medical information for patients [7]. The view counts of YouTube videos have been dramatically increased during the pandemic [22]. In the present study, we tried to determine the reliability and quality of YouTube videos concerning myocarditis. In our study, the most commonly viewed video content was general information regarding myocarditis followed by COVID-19 vaccination and myocarditis.

General performance of a video may be measured with the view, like dislike and comment counts. These parameters can provide basic information about the performance of a video. In the present study, the mean number of views was found as 324,035, likes as 3022, dislikes as 336.52 and comments as 434. Undoubtedly, these numbers show great differences between the studies depending on the subject of the research.

The qualification of the uploaders has a significant effect on the reliability and quality of YouTube videos. As is known, anyone can freely upload videos on this platform that has still no a regulation or peer review process for the uploaded videos. In the present study, most videos (44%) were uploaded by health channels followed by physicians (28%) and hospital channels (20%). Only 8% of the videos were uploaded by lay persons. In a study by Cetin et al. examining YouTube videos on hyperglycemia, the videos were most commonly uploaded by health channels (54%) [12]. In another study by Fode et al., 42% of the YouTube videos pertaining to erectile dysfunction were uploaded by health channels [23]. In this regards, studies have similar results indicating that health channels are the most common video uploaders. On the other hand, most of the videos uploaded by health channels about any medical topic include physician(s) as narratives. Again in our study, the highest view and like counts were found in the videos uploaded by health channels.

In the present study, the mean Video Power Index that indicates the popularity of videos based on daily views, like and dislike counts was calculated as 92.89. The highest VPI index score was found in the videos uploaded by patients (99.49) and those with patient experience (98.76). In a study by Yurdaisik et al. including YouTube videos concerning breast cancer, the mean VPI was reported as 94.10 [13]. In a study by Kuru et al., YouTube videos on rotator cuff tears were examined and the mean video power index value was found as 90.6 [10]. In another study by Cakmak et al. on the YouTube videos concerning umbilical hernia, the mean VPI was found as 90.25, while the videos uploaded by non-doctors had a higher VPI compared to the videos uploaded by doctors [24]. Several studies have reported that YouTube videos uploaded by lay persons are of poor quality, although these videos have higher rates of like and VPI values [25]. We attributed this result to the fact that video contents uploaded by healthcare physicians may have medical language that may not be understood by everyone, making the videos including patient experience that are narrated by lay persons more popular.

In our study, the reliability of YouTube videos pertaining to myocarditis was measured using the modified DISCERN criteria. Accordingly, the mean DISCERN score of the overall videos was found as 3.88. When DISCERN scores were analyzed according to the general characteristics, the highest mean DISCERN score was found as 4.32 for the videos uploaded directly by physicians followed by 3.82 for the videos uploaded by health channels. The lowest DISCERN score was 2.75 for the videos uploaded by patients. Based on the DISCERN scoring, reliability was found as poor in 4%, moderate in 14% and good in 82% of the videos about myocarditis. Based on the contents, the highest DISCERN score (4.21) was given to the videos containing the association of myocarditis and COVID-19 vaccination, indicating that these videos contain reliable information to guide and motivate people for being vaccinated.

Because the vast majority of health-related YouTube studies in the literature have been conducted in a wide range of diseases and medical conditions, making a direct comparison for reliability score is challenging. Besides, some studies have used 30-item DISCERN scoring, while the others have utilized the modified 5-item DISCERN as in our study. Nevertheless, looking at the several studies in the literature; the mean DISCERN score of YouTube videos on erectile dysfunction was found as ≤ 3 with the highest score given to the videos uploaded by medical institutions [23]. The mean DISCERN score was reported as 2.35 by Akpolat et al. [26], 1.91 by Wu et al. [27], and 3.00 by Onder et al. [28]. In general, the above-mentioned studies have reported higher DISCERN scores for the videos uploaded by healthcare professionals. Our higher DISCERN scores compared to the other study might be caused by the fact that association of myocarditis and COVID-19 is a hot topic and especially health channels and other professionals are trying to provide more reliable information to promote people for COVID-19 vaccination.

In the present study, the mean GQS score was found as 3.63, which indicates moderate quality. Again the highest GQS score was given to the videos uploaded by physicians (3.89) followed by health channels (3.84), while the lowest score was given to those uploaded by patients (2.50), which shows poor quality. Based on GQS scoring, the quality of the viewed YouTube was found as moderate. The mean GQS score was reported as 4.00 by Onder et al. [28], 3.08 by Ustdal et al. [29], and 2.46 by Oztermeli et al. [30] with higher GQS scores were given to the videos uploaded by health professionals. Again our higher GQS scores might be attributed to the fact that the majority of the videos were uploaded by health professionals.

In our study, the reliability and quality of YouTube videos concerning myocarditis were found as moderate. However, the videos uploaded by health professionals, including physicians and health channels, received higher scores compared to the videos uploaded by hospitals (may include indirect ads) and lay persons.

This study has several limitations. First, evaluation of the videos is subjective and there is still no validated tool for objective evaluation. Second, YouTube search results are dynamic, and change when new contents are uploaded. Therefore, this study shows the reliability and quality of the videos at a specific time.