Abstract #2504

Human cardiac pH and Pi concentration during dobutamine stress measured by 7T 31P-MRS

Albrecht Ingo Schmid^1,2, Andrew P Apps², Ladislav Valkovic^2,3, Elisabeth Tunnicliffe², William T Clarke⁴, Mark A Peterzen², Stefan Neubauer², Oliver J Rider², and Christopher T Rodgers^2,5

¹Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ²Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, Oxford, United Kingdom, ³Department of Imaging Methods, Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia, ⁴Wellcome Centre for Integrative Neuroimaging, FMRIB, University of Oxford, Oxford, United Kingdom, ⁵The Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom

The hydrolysis of adenosine triphosphate (ATP) to adenosine diphosphate (ADP) in the reaction ATP + H20 ⇌ ADP + P_i (inorganic phosphate) is used to drive all cellular processes, including those involved in ventricular contraction and relaxation. When spectral quality is sufficient to quantify the Pi peak, it is possible to assess the ratio of P_i to phosphocreatine (P_i/PCr), which is an established measure of the muscle control of energy production. It is also possible to assess cardiac intracellular pH from the P_i to PCr frequency offset. Most human cardiac ³¹P-MRS studies report only the PCr/ATP ratio, and are typically unable to quantify cardiac Pi because of partially overlapping resonances from 2,3-diphosphoglycerate in blood. We aimed to use ultra-high (7T) field strength and a novel ³¹P STEAM sequence to 1) non-invasively measure myocardial Pi/PCr and pH at rest and 2) for the first time record these parameters during catecholamine stress.

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