Quantifying the effect of dobutamine stress on myocardial Pi and pH in healthy volunteers: A 31 P MRS study at 7T.

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Valkovič, Ladislav  ORCID logo  https://orcid.org/0000-0003-2567-3642
Peterzan, Mark 
Hundertmark, Moritz 

PURPOSE: Phosphorus spectroscopy (31 P-MRS) is a proven method to probe cardiac energetics. Studies typically report the phosphocreatine (PCr) to adenosine triphosphate (ATP) ratio. We focus on another 31 P signal: inorganic phosphate (Pi), whose chemical shift allows computation of myocardial pH, with Pi/PCr providing additional insight into cardiac energetics. Pi is often obscured by signals from blood 2,3-diphosphoglycerate (2,3-DPG). We introduce a method to quantify Pi in 14 min without hindrance from 2,3-DPG. METHODS: Using a 31 P stimulated echo acquisition mode (STEAM) sequence at 7 Tesla that inherently suppresses signal from 2,3-DPG, the Pi peak was cleanly resolved. Resting state UTE-chemical shift imaging (PCr/ATP) and STEAM 31 P-MRS (Pi/PCr, pH) were undertaken in 23 healthy controls; pH and Pi/PCr were subsequently recorded during dobutamine infusion. RESULTS: We achieved a clean Pi signal both at rest and stress with good 2,3-DPG suppression. Repeatability coefficient (8 subjects) for Pi/PCr was 0.036 and 0.12 for pH. We report myocardial Pi/PCr and pH at rest and during catecholamine stress in healthy controls. Pi/PCr was maintained during stress (0.098 ± 0.031 [rest] vs. 0.098 ± 0.031 [stress] P = .95); similarly, pH did not change (7.09 ± 0.07 [rest] vs. 7.08 ± 0.11 [stress] P = .81). Feasibility for patient studies was subsequently successfully demonstrated in a patient with cardiomyopathy. CONCLUSION: We introduced a method that can resolve Pi using 7 Tesla STEAM 31 P-MRS. We demonstrate the stability of Pi/PCr and myocardial pH in volunteers at rest and during catecholamine stress. This protocol is feasible in patients and potentially of use for studying pathological myocardial energetics.

31P MRS, 7T, STEAM, cardiac energetics, myocardial pH, Adenosine Triphosphate, Dobutamine, Humans, Hydrogen-Ion Concentration, Magnetic Resonance Spectroscopy, Myocardium, Phosphates, Phosphocreatine
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Magn Reson Med
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Wellcome Trust (Unknown)
Wellcome Trust (098436/Z/12/B)
AA [FS/17/18/32449] and MP [FS/15/80/31803] are supported by British Heart Foundation Clinical Research Training Fellowships. OJR is supported by a British Heart Foundation Intermediate Fellowship. DT is supported by a British Heart Foundation Senor Fellowship [FS/14/17/30634]. DT, JL and EMT are supported by the National Institute for Health Research (NIHR) Oxford Biomedical Research Centre. SN acknowledges the support of the Oxford BHF Centre of Research Excellence. CTR and LV are funded by the Wellcome Trust and the Royal Society [098436/Z/12/B]. AIS was supported through the Austrian Science Fund’s (FWF) Schrödinger fellowship (J 4043). LV also acknowledges support of the Slovak Grant Agencies VEGA [2/0003/20] and APVV [#19–0032]. This research was also supported by the NIHR Cambridge Biomedical Research Centre. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.