Abstract #0349

Imaging of Whole Body Oxygen Consumption and its Fick Determinants During Exercise: Real-Time Exercise CMR and Venous Oximetry

Stephen Foulkes¹, Rachel Skow¹, Justin Grenier¹, Corey Tomczak², Dean Perkins³, Hendrik Mugele³, Michael Nelson⁴, Andre La Gerche⁵, Justin Lawley³, Mark Haykowsky¹, and Richard Thompson¹

¹University of Alberta, Edmonton, AB, Canada, ²University of Saskatchewan, Edmonton, AB, Canada, ³University of Innsbruck, Innsbruck, Austria, ⁴University of Texas at Arlington, Arlington, TX, United States, ⁵St Vincent's Institute of Medical Research, Melbourne, Australia

Synopsis

Keywords: Task/Intervention Based fMRI, Cardiovascular, Exercise

Motivation: There is a need for non-invasive approaches to determine the central (cardiac output, CO) and peripheral (arterio-venous oxygen difference, a-vO₂diff) determinants of oxygen uptake (VO₂) during exercise.

Goal(s): Validate an approach (MRI_Fick) combining real-time cardiac magnetic resonance (CMR)-derived cardiac-output and real-time venous susceptometry-based oximetry (MR_Oximetry, for deriving venous oxygen saturation, SvO₂, in the inferior vena cava and the a-vO₂diff) to calculate the VO₂ during exercise.

Approach: CMR and MR_Oximetry scans were acquired with simultaneous pulmonary VO₂ (reference standard) during progressive stepping exercise (50W increments to fatigue) in young adults (n=17).

Results: MRI_Fick showed excellent agreement (R²=0.95) for measuring whole-body VO₂ during stepping exercise.

Impact: An MRI approach that combines real-time CMR with magnetic-susceptometry-based measures of SvO2 is feasible and allows for accurate quantification of peak VO₂ and its Fick determinants (CO x a-vO₂diff) without the need for invasive catheters.

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