Normal values for native T1 and gadolinium-based contrast agent excretion into pericardial fluid in healthy volunteers – comparison with patients with pericardial effusion

T1 mapping cardiovascular magnetic resonance (CMR) imaging has been used to characterize pericardial effusions, and shown that routinely administered gadolinium-based contrast agents (GBCA) are excreted into effusion fluid. Aims To measure pericardial fluid T1 before and after contrast administration in healthy volunteers to establish normal values and compare them to patients with pericardial effusion. Volunteers (n=30) were compared to retrospectively included patients with at least 5 mm of pericardial effusion (n=69). T1 maps were acquired at 1.5T CMR. A volume of pericardial fluid was imaged in a short-axis slice and in a slice perpendicular to the short-axis orientation. A reliable measurement had a region of interest size >10mm2, coefficient of variation <10%, and a relative difference <5% between the two slice orientations. In 26/30 (87%) of volunteers, there was a sufficient amount of pericardial fluid to enable reliable measurement. Native T1 did not differ between slice orientations (3262±163 vs 3267±173 ms, p=0.75). In patients, native T1 was normal in 41%, above normal in 3%, below normal in 56%, and GBCA concentration, estimated using the specific relaxivity of the GBCA used, was normal in 65% and above normal in 35%. More than half of effusions in patients had a native T1 below normal, consistent with higher protein content, and a third had an above normal GBCA excretion despite dilution effects, suggesting an inflammatory and exudative etiology. The use of T1 mapping and contrast dynamics to characterize pericardial fluid merits prospective evaluation. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The Swedish Heart Lung Foundation ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by the Swedish Ethical Review Authority and conducted according to the principles of the Declaration of Helsinki. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors