Assessment and validation of the established free-running framework for cardiac function by magnetic resonance...

Cardiovascular magnetic resonance (CMR) is the reference standard for assessing cardiac function, yet its widespread clinical use remains challenged by time-intensive workflows requiring ECG gating, repetitive breath-holding, and expert planning. The free-running framework (FRF) addresses these barriers by enabling respiratory and cardiac motion resolved (5D) whole-heart imaging without ECG, breath-holds, or expert scan plane planning. Its fast interrupted steady-state (FISS) variant further enables high quality clinical imaging with gadolinium-based or ferumoxytol contrast agents by providing balanced steady-state free precession (bSSFP)-like contrast with intrinsic fat suppression. The combined 5D FISS-FRF approach, therefore, enables 3D, motion-resolved, free-breathing whole-heart imaging with efficient fat suppression. Early single-center studies have demonstrated feasibility and high concordance with conventional 2D cine imaging, but its generalizability and clinical utility in a multi-center, multi-vendor setting is not yet established.

FAST-CMR (Assessment and validation of the established free-running framework for cardiac function by magnetic resonance imaging) is a prospective, observational, intra-individually controlled, pragmatic multi-center study enrolling 300 patients with cardiac disease across 21 international sites from 6 continents using 1.5T MR systems of both Siemens Healthineers and Philips Healthcare. Patients will undergo conventional 2D cine bSSFP CMR in both short-axis and long-axis orientations and a post-contrast 5D FISS-FRF acquisition of six minutes in length. Stratification will include equal representation across three disease cohorts: patients with congenital heart disease (CHD), patients unable to breath-hold, and patients who are able to breath-hold. 5D FISS-FRF raw image acquisition data will undergo centralized reconstruction at the coordinating center (CHUV) before blinded analysis at the core laboratory (Mayo Clinic). The primary endpoint is the precision of the mean paired difference in left ventricular ejection fraction (LVEF) between 5D FISS-FRF and conventional 2D cine CMR, assessed on a within-subject basis. Agreement will be further characterized using confidence intervals for the mean difference and Bland-Altman analysis. Secondary endpoints include detection of regional wall-motion abnormalities, image quality, scan efficiency, patient comfort, LV mass, left and right atrial volumes, and feasibility of automated post-processing and artificial intelligence (AI)-based reconstruction.

FAST-CMR will provide the first prospective international multi-center, multi-vendor evaluation of 5D FISS-FRF. By combining standardized acquisition, centralized reconstruction, and harmonized analysis across 21 international sites and two vendor systems, the study will assess the generalizability and robustness of ventricular functional measurements obtained with 5D FISS-FRF. Using a pre-specified precision-based framework for global ventricular function and complementary agreement analyses, FAST-CMR will evaluate whether 5D FISS-FRF can provide measurements that are comparable to conventional 2D cine across diverse clinical settings, while potentially offering improvements in workflow, scan efficiency and patient experience. These results will inform future studies assessing clinical interchangeability with conventional 2D cine imaging and implementation in routine CMR practice.