From May 2020 to May 2021, the investigators retrospectively evaluated clinical cardiac magnetic resonance (CMR) examinations performed in patients with suspected cardiac involvement post COVID-19. Between May 2021 and August 2021, the investigators evaluated patients with suspected cardiac disease after COVID-19 vaccination.

Hospital database for patients that underwent a clinical CMR examination between May 2020 and May 2021 for suspected cardiac pathology post COVID-19 were analyzed. For comparison, CMR examinations from January until August 2021 were searched for suspected cardiac pathology post COVID-19 vaccination. The study complies with the declaration of Helsinki and was approved by the ethics committee of the Charité-Universitätsmedizin Berlin (EA2/020/21).

CMR Imaging All scans were performed for clinical indications on either a Philips Ingenia 3.0 T scanner or a Philips Ambition 1.5 T scanner according to recent recommendations for CMR in patients post COVID-19. Protocols were adjusted to the clinical scenario but generally included standard CINE imaging, T2 STIR edema imaging, basal and medial short axis T2 mapping (T2-GraSE) and pre- and post-contrast T1 mapping (MOLLI), and Late-Enhancement-Imaging (mDIXON). Vasodilator stress with Regadenosone or Adenosine was performed in patients with clinically suspected myocardial ischemia. The Adenosine dose was 0.140 µg/kg/min, with an increase to 0.210 µg/kg/min in case of insufficient response. The Regadenosone dose was 200µg irrespective of weight, followed by Theophyllin reversal as needed (max. 200mg). The contrast agent was 0.1 mmol/kg Gadobutrol (Gadovist®, Bayer AG, Leverkusen, Germany).

CMR image analysis Image post-processing and measurements were performed according to recent recommendations using dedicated CMR post-processing software (IntelliSpace Portal V11.1, Philips, Best, The Netherlands). The diagnosis of 'probable myocarditis' was based on the updated Lake Louise Criteria requiring findings of myocardial damage (LGE) and edema (T2 STIR or T2 mapping) in a non-ischemic pattern (intramyocardial or subepicardial). Evidence of edema without myocardial damage was considered 'possible myocarditis' whereas myocardial damage without edema was considered 'subsided myocarditis.

Inclusion Criteria:

• Cardiac MRI for suspected cardiac Involvement after COVID-19 or COVID-19-vaccination

Exclusion Criteria:

• None

Clinical all-comers with suspected cardiac Involvement after COVID-19 or COVID-19-vaccination