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Background: Despite the ongoing global pandemic, the impact of COVID-19 on cardiac structure and function is still not completely understood. Myocarditis is a rare but potentially serious complication of other viral infections with variable recovery, and is, in some cases, associated with long-term cardiac remodeling and functional impairment.Aim: To assess myocardial injury in patients who recently recovered from an acute SARS-CoV-2 infection with advanced cardiac magnetic resonance imaging (CMR) and endomyocardial biopsy (EMB).Methods: In total, 32 patients with persistent cardiac symptoms after a COVID-19 infection, 22 patients with acute classic myocarditis not related to COVID-19, and 16 healthy volunteers were included in this study and underwent a comprehensive baseline CMR scan. Of these, 10 patients post COVID-19 and 13 with non-COVID-19 myocarditis underwent a follow-up scan. In 10 of the post-COVID-19 and 15 of the non-COVID-19 patients with myocarditis endomyocardial biopsy (EMB) with histological, immunohistological, and molecular analysis was performed.Results: In total, 10 (31%) patients with COVID-19 showed evidence of myocardial injury, eight (25%) presented with myocardial oedema, eight (25%) exhibited global or regional systolic left ventricular (LV) dysfunction, and nine (28%) exhibited impaired right ventricular (RV) function. However, only three (9%) of COVID-19 patients fulfilled updated CMR–Lake Louise criteria (LLC) for acute myocarditis. Regarding EMB, none of the COVID-19 patients but 87% of the non-COVID-19 patients with myocarditis presented histological findings in keeping with acute or chronic inflammation. COVID-19 patients with severe disease on the WHO scale presented with reduced biventricular longitudinal function, increased RV mass, and longer native T1 times compared with those with only mild or moderate disease.Conclusions: In our cohort, CMR and EMB findings revealed that SARS-CoV-2 infection was associated with relatively mild but variable cardiac involvement. More symptomatic COVID-19 patients and those with higher clinical care demands were more likely to exhibit chronic inflammation and impaired cardiac function compared to patients with milder forms of the disease.

Introduction: CMR 4D flow is a promising technique for assessing vessel hemodynamics. However, its current utilization is limited due to the lack of reference values, particularly for pulmonary vessels, generally understudied. With the purpose to serve for future research studies, we have analysed the pulmonary flow and velocity in Landrace pigs at both rest and stress by utilizing the software MEVISFlow. Methods: Nine (n=9) healthy Landrace pigs were acutely instrumented closed-chest and transported to the CMR facility for evaluation. After baseline (BL) measurements, dobutamine (Dob) was administrated to achieve a 25% increase in heart rate compared to baseline values. 4D flow images from the pigs during both rest and stress states have been analysed through MEVISFlow software by two independent observers. In detail, we examined peak flow and peak velocity of the pulmonary trunk (PT) and both left and right pulmonary arteries (LPA and RPA, respectively). Results: A significant difference between BL and Dob regarding both peak flow and peak velocity in all the pulmonary vessels was observed. Peak flow changed from 0.09 L/min to 0.14 L/min in PT, from 0.04 L/min to 0.07 L/min in LPA and from 0.05 L/min vs 0.07 L/min in RPA. Peak velocity changed from 0.90 m/s to 1.40 m/s in PT, from 0.80 m/s to 1.40 m/s in LPA and from 0.80 m/s to 1.33 m/s in RPA. Conclusions: The current study showed that peak flow and peak velocity assessed through pulmonary 4D flow follow the physiological alterations during systole and diastole and after stress induced by dobutamine.