key: cord-0986035-7fociv5v authors: Heiss, R.; Wagner, A. L.; Tan, L.; Schmidt, S.; Regensburger, A. P.; Ewert, F.; Mammadova, D.; Buehler, A.; Vogel-Claussen, J.; Voskrebenzev, A.; Rompel, O.; Nagel, A. M.; Levy, S.; Bickelhaupt, S.; May, M. S.; Uder, M.; Metzler, M.; Trollmann, R.; Woelfle, J.; Knieling, F. title: Persisting pulmonary dysfunction in pediatric post-acute Covid-19 date: 2022-02-22 journal: nan DOI: 10.1101/2022.02.21.22270909 sha: 84d13b0261d23c0b1528123cee970f761d326d6d doc_id: 986035 cord_uid: 7fociv5v The frequency and extent of persistent sequelae in children and adolescents after infection with SARS-CoV-2 still needs to be comprehensively determined. In this cross-sectional clinical trial, we used non-invasive, label-free morphologic and free-breathing phase-resolved functional low-field magnetic resonance imaging (LF-MRI) to identify pulmonary changes in children and adolescents from 5 to <18 years after previously PCR-confirmed SARS-CoV-2 infection. While morphological pathologies were less frequent in children, functional LF-MRI visualized widespread ventilation, perfusion and combined ventilation/perfusion defects compared to healthy controls. The loss of functional lung parenchyma was more pronounced in long Covid than recovered patients. While pulmonary dysfunction was persistent even month after primary infection, LF-MRI demonstrated high capability to visualize and detect these changes in children and adolescents. (Clinicaltrials.org ID NCT04990531) SARS-CoV-2 has emerged as a global pandemic causing more than 280 million documented infections and 5.4 million deaths until the end of 2021. 1 In comparison to adults, there is common evidence that Covid-19 in children and adolescents has a milder course with recovery within weeks. 2 This finding is compromised by a growing body of evidence for postacute sequelae and symptoms in these age classes. [2] [3] [4] While there is an increasing understanding of the multi-organ damage of Covid-19 beyond the acute phase of infection 5 , the nature, frequency and definition of post-acute sequelae in children and adolescents still remains undetermined with a discrepancy in clinical appearance and objective findings. 6 A major proportion of pediatric studies have lately prioritized research in mental health issues during the Covid-19 pandemic 7-10 , while other studies have already raised concerns on ongoing disease manifestations, including increased thrombotic state, microangiopathy and inflammation. [11] [12] [13] As the lung is a primary target of the SARS-CoV-2 virus, 14 computed tomography aided in the diagnosis of pulmonary manifestation of Covid-19 in adults. 15 Even three months after infection, angiographic imaging of pulmonary microcirculation still revealed widespread microangiopathy in over 65% of the patients. 16 Such techniques using invasive procedures or ionization radiation are not feasible in children and also seem to have limited diagnostic value as lung parenchymal changes do present less obvious and pronounced. [17] [18] [19] Therefore, there is an unmet clinical need to more precisely characterize pulmonary manifestations in children and adolescents after SARS-CoV 2 infection. We used low-field magnetic resonance imaging (LF-MRI) for imaging of the pediatric lung. At low field strength, this technique has improved imaging quality of near air-tissue interfaces, without the need for ionizing radiation. 20, 21 The aim of the study was to characterize both morphologic and functional changes of lung parenchyma in PCR-proven SARS-CoV-2 pediatric post-acute Covid-19 patients in comparison to healthy controls. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) We performed a single-center, cross-sectional, investigator-initiated trial to investigate lung parenchymal changes in children and adolescents after SARS-CoV-2 infection. The call for study participation for Covid-19 patients was nationwide public and consecutive. After assessment for clinical parameters, a blood sample was drawn and all patients underwent LF-MRI. Clinical features during and after infection, the time period from positive PCR test and laboratory parameters were compared to imaging results. Details are provided in the protocol and the statistical analysis plan. The coordinating clinical investigators were responsible for data collection and site monitoring. The first authors and corresponding author had constant access to the data and performed the statistical analysis as well as the creation of the first draft of the manuscript independently from any commercial facility. All participants in both cohorts were between 5 and <18 years of age. In the Covid-19 group, eligible patients required a positive PCR-test for SARS-CoV-2 in the prior history. The definition for long Covid was based on the persistence of symptoms for a minimum of 12 weeks and either one of the four criteria: 22,23 1) Symptoms that persist from the acute Covid-19 phase or its treatment, 2) Symptoms that have resulted in a new health limitation, 3) New symptoms that occurred after the end of the acute phase but are understood to be a consequence of Covid-19 disease, 4) Worsening of a pre-existing underlying condition. In the healthy control group, children required a negative medical history, post-hoc negative serological antibody status, and no prior immunization against SARS-CoV-2. The primary outcome was the determination of the frequency of morphological changes of lung parenchyma by LF-MRI. Secondary outcomes included functional lung changes comprising ventilation defects (ventilation defected percentage; VDP Total ), perfusion defects (perfusion defected percentage; QDP Total ), the match (ventilation/perfusion match; VQM Nondefect ) and match (defect) of both (ventilation/perfusion defect; VQM Defect ), laboratory assessments and anamnestic clinical symptoms. Patients were assessed for medical history, including symptoms during and after Covid-19 infection. Blood pressure and heart rate were measured from each individual. A blood sample was collected to assess blood count, interleukin 6 (IL-6), C-reactive protein (CrP) and antibodies against SARS-CoV-2 (spike protein and nucleocapsid antibodies, For free-breathing phase-resolved functional lung (PREFUL) LF-MRI, the following parameters were calculated voxel-wise by using a dedicated software (MR Lung v2.0, . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted February 22, 2022. ; Siemens Healthcare, Erlangen, Germany) after automatic registration to a mid-expiration position and lung parenchyma segmentation. 26 Normalized perfusion (Q, %) with respect to a full-blood signal region, determined as the highest perfusion signal region in-between the lungs and expected to reflect the aorta or other available large vessel 27 ; Regional ventilation (V, %) calculated as: were calculated. An overview and explanation of all parameters used is given in Table S1 . PREFUL MRI ventilation and perfusion measures were recently validated using V/Q single photon emission tomography, dynamic contrast enhanced MRI as well as 19 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. Table S1) . Detailed acute and post-acute Covid-19 symptoms can be found in Table S2 . 4 patients with PCR-positive SARS-CoV2 infection did not show any symptoms during acute infection. None of the Covid-19 patient group required hospital admission during the primary infection period. The median interval between positive SARS-CoV-2 PCR test and study participation was 222±134 days. There were no missing primary and/or secondary outcome data. Of the 54 post-acute Covid-19 and 9 healthy controls scanned with LF-MRI, 1 recovered Covid-19 patient showed morphological changes with pulmonary consolidations (Figure S1 ). Figure 2 ; the corresponding morphologic images are shown in Figure S3 . Inflammation parameters including CrP, IL-6 and blood counts were not suggestive of a current infection at the day of study for any participant. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. even increasing as SARS-CoV-2 incidence is rising in most countries. 36 Pathophysiology of acute and post-acute pathology of Covid-19 partly originates from direct endothelial damage, local inflammation and prothrombotic milieu. 14,37-39 A proposed mechanism is the ACE2-mediated entry of SARS-CoV-2, which allows the virus to directly invade endothelial cells. 14, 40 This may explain manifestations such as pulmonary microangiopathy and widespread capillary microthrombi seen in autopsies from patients who died from Covid-19 14 and fibrotic-like consolidations found in computed tomography. 33 Previously described 13 persisting signs of inflammatory processes could not be confirmed in our study. Putting into context, that children develop a robust, cross-reactive and sustained immune response after SARS-CoV-2 infection 41 , the observed pulmonary dysfunction in our study is an unexpected finding. This trial has several limitations. We did not compare our measurements to another reference standard, such as ventilation-perfusion scintigraphy, spirometry or body plethysmography. However, most of these modalities either use ionization radiation, are invasive or require . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted February 22, 2022. ; https://doi.org/10.1101/2022.02.21.22270909 doi: medRxiv preprint active cooperation. In addition, validation of our imaging approach has been described previously 26, 29 . The functional LF-MRI in our study used free-breathing all intervals, which was feasible in 93% of the pediatric post-acute Covid-19 patients starting from 5 years of age. Given our technical setup, measurements of functional lung parenchyma had systematically lower values as reported before, 28, 30, 42 which does not alter our comparisons between the investigated groups. Further limitations include the lack of longitudinal data as well as the lower number of healthy controls. Finally, a selection bias could exist, as a majority of families with acute or post-acute symptomatic children and higher disease burden might have participated in the study. However, we obtained a balanced cohort with 24 (44%) long Covid patients, putting this potential bias into perspective. In summary, we report persisting pulmonary dysfunction both in pediatric patients recovered The data sets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request as follows: Individual participant data will not be available. Study Protocol and Statistical Analysis Plan will be available. All data will be available beginning 9 months and ending 36 months following article publication. The data will be available to researchers who provide a methodologically sound proposal. The data will be available for individual participant data meta-analysis, only. Proposals may be submitted up to 36 months following article publication. After 36 months the data will be available in our university's data warehouse but without investigator support other than deposited metadata. Information regarding submitting proposals and accessing data may be found at https://www.uk-erlangen.de. Restrictions may apply due to patient privacy and the General Data Protection Regulation. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted February 22, 2022. ; https://doi.org/10.1101/2022.02.21.22270909 doi: medRxiv preprint No previously unreported custom computer code or algorithm was used to establish results in this paper. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted February 22, 2022. ; . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. From left to right: Representative functional low-field magnetic resonance images for ventilation defects, perfusion defects and combined defects in a healthy control (upper row), a recovered patient (middle row) and a long Covid patient (lower row). . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 22, 2022. ; https://doi.org/10.1101/2022.02.21.22270909 doi: medRxiv preprint Receiver operator characteristics (ROC) curve for ventilation defects, perfusion defects, ventilation/perfusion match (non-defect) and ventilation/perfusion match (defect) in recovered (n=29) and long Covid (n=25) patients versus healthy controls (n=9). . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 22, 2022. ; https://doi.org/10.1101/2022.02.21.22270909 doi: medRxiv preprint WHO Health Emergency Dashboard. in WHO (COVID-19) Homepage Post-acute COVID-19 outcomes in children with mild and asymptomatic disease Preliminary evidence on long COVID in children Long-term Symptoms After SARS-CoV-2 Infection in Children and Adolescents Post-acute COVID-19 syndrome How Common is Long COVID in Children and Adolescents? 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