Validation of Left Ventricular High Frame Rate Echo-Particle Image Velocimetry against 4D Flow MRI in Patients

Background: Accurately measuring blood flow patterns in the heart could provide insights in the pathophysiology of cardiac disease, and may provide additional diagnostic and prognostic information. This study aims to validate Echo-Particle Image Velocimetry (echoPIV) for in-vivo left ventricular intracardiac flow imaging by comparing it with 4D flow MRI. Methods: We acquired HFR contrast-enhanced ultrasound images from three standard apical views of 26 patients who required cardiac MRI. 4D flow MRI was obtained for each patient. Only echo image planes with sufficient quality and alignment with MRI were included for the validation. Regional velocity, kinetic energy and viscous energy loss were compared between modalities using normalized mean absolute error, cosine similarity and Bland-Altman analysis. Results: Among 24 included apical view acquisitions, we observed good correspondence between echoPIV and MRI regarding spatial flow patterns and vortex traces. The velocity profile at the cross-section at the base level (mitral valve) had cosine similarity of 0.92 ± 0.06 and normalized mean absolute error of 14 ± 5%. Peak of spatial mean velocity showed a difference of 3 ± 6 cm/s in systole and 6 ± 10 cm/s in diastole. The kinetic energy and rate of energy loss also revealed a high level of cosine similarity (0.89 ± 0.09 and 0.91 ± 0.06 ) with normalized mean absolute error of 23 ± 7% and 52 ± 16%. Conclusions: Given good B-mode image quality, echoPIV can provide a reliable estimation of left ventricular flow, as compared with 4D flow MRI, providing comparable spatial-temporal velocity distributions. There are advantages and disadvantages for both modalities. EchoPIV captured inter-beat variability and had higher temporal resolution, while MRI was more robust to patient BMI and anatomy. ### Competing Interest Statement A. Hirsch received a research grant and consultancy fees from GE Healthcare and speaker fees from GE Healthcare and Bayer. He is also a member of the medical advisory board of Medis Medical Imaging Systems and was MRI corelab supervisor of Cardialysis BV until 2022. ### Funding Statement The work described in this article was funded by the Medical Delta program "Ultrafast Ultrasound for the Heart and Brain"; the project X-Flow of the research program Ultra-X-Treme (P17-32), which is financed by the Dutch Research Council (NWO); and the Dutch Heart Foundation (Hartstichting) as part of project number 03-004-2022-0044. ### 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: This study was approved by the Erasmus MC Medical Ethic Review Committee (Rotterdam, the Netherlands), and written informed consent was obtained from all patients (METC-2018-057, NL63755.078.18) 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 Data is available on reasonable request