Normal values for mitral and tricuspid early inflow blood flow velocity variation using real time phase contrast cardiovascular magnetic resonance

Background Diastolic ventricular interdependence influences the breathing-induced variation in early diastolic blood flow velocities across the mitral and tricuspid valve. The aim of this study was to develop a method to measure the respiratory variation in mitral and tricuspid early inflow velocities using semi-automatic analysis of real time phase contrast (RT-PC) cardiovascular magnetic resonance (CMR) images, and describe normal reference values. Methods Clinically referred patients (n=24, median [interquartile range] age 55 [46– 65] years, 48% female) with no pericardial effusion or pericardial thickening underwent through-plane RT-PC CMR imaging using a research sequence at 3T in a basal short-axis view over a 30 s acquisition during free breathing. One patient with constrictive pericarditis and one patient with a hemodynamically significant pericardial effusion were imaged to illustrate clinical feasibility. Image analysis was performed using an in-house developed plugin. A region of interest was prescribed over encompassing the mitral and tricuspid orifices, respectively. The highest (Vmax) and lowest (Vmin) early inflow velocities were then automatically recorded. Respiratory variation was defined as (Vmax-Vmin)/Vmax. Results The respiratory variation in mitral and tricuspid early inflow velocity in patients without constrictive pericarditis or pericardial effusion was (mean±SD) 22±7% (upper limit 35%) and 38±7% (upper limit 51%). The patient with constrictive pericarditis had a respiratory variation in mitral and tricuspid early inflow velocities of 60% and 44%, respectively. The patient with 35 mm pericardial effusion had a respiratory variation in mitral and tricuspid early inflow velocities of 62% and 64%, respectively. ### Competing Interest Statement EH is the founder of Medviso AB, Lund, Sweden, which sells a commercial version of the software Segment. ### Funding Statement The research was funded in part by the Swedish Research Council, Swedish Heart and Lung Foundation, the Stockholm County Council and Karolinska Institutet. Karolinska University Hospital has a research and development agreement regarding CMR with Siemens Healthineers. ### 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: Approval from the Stockholm regional ethics board was obtained (Number 2011/1077-31/3). 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, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors