BS58 Whole heart phosphorous spectroscopy at 7 tesla detects regional myocardial differences in cardiac metabolism

Introduction Metabolic inflexibility is a key feature of the failing heart, with myocardial metabolism a promising therapeutic target in heart failure. Phosphorus (31P) magnetic resonance spectroscopy monitors cardiac energetics in vivo. Previous studies have shown that the PCr/ATP ratio predicts mortality,¹ however widespread use in clinical trials has been hampered so far by relatively low sensitivity and low spatial resolution. As many cardiac conditions affect the myocardium heterogeneously, being able to produce data localised to individual myocardial segments could produce valuable diagnostic or research data. Methods We used a novel transmit/receive dipole array with 8Tx/24Rx for 31P and 8 Tx/Rx for 1H (Tesla Dynamic Coils). For this study, we transmitted with the four central 31P dipoles which cover the heartThe protocol comprised anatomical localisation, B1 calibration and a 30-min 31P CSI scan as previously described² ³ with 1s TR, 450 V excitation, a 20x20x12 3D matrix over a 30x35x40 cm3 FOV run on a 7T Terra MRI scanner (Siemens). Data were processed in Matlab using an extended version of OXSA.⁴ This was complemented with a cardiac imaging protocol on a 3T Prisma MRI scanner (Siemens). Data were analysed in Circle CVI42. Six healthy volunteers were scanned (3F+3M, aged 24 to 39 years). Results Cardiac function was normal in the cohort (mean LVEF 57 ± 4 %). Spectral quality was good (mean SNR 24.4, SD 7.3, figure 1). Mean septal PCr/ATP was 1.69 ± 0.2. PCr/ATP tended to be higher in the free walls (anterior wall 2.3 ± 0.38, inferior wall 1.98 ± 0.45, lateral wall 2.53 ± 0.56). Septal PCr/ATP correlates with global longitudinal strain (R2 = 0.67, p = 0.046, figure 2). Segmental PCr/ATP values showed a trend with segmental radial strain (R2 = 0.175, p = 0.059) and circumferential strain (R2 = 0.161, p = 0.071). Conclusions Our novel dipole coil is produces data of good quality. We present the first evidence of a correlation between cardiac energetics (PCr/ATP) and indices of contractility on a per-segment basis. This paves the way for spectroscopy research in heterogenous myocardial conditions. Acknowledgement This study was funded by Innovate UK (10032205) under the Guarantee Scheme relating to the EU Horizon Europe project MITI (101058229). This research was supported by the NIHR Cambridge Biomedical Research Centre (BRC-1215–20014). The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care. References 1. Neubauer S, Horn M, Cramer M, Harre K, Newell JB, Peters W, Pabst T, Ertl G, Hahn D, Ingwall JS, Kochsiek K. Myocardial phosphocreatine-to-ATP ratio is a predictor of mortality in patients with dilated cardiomyopathy. Circulation 1997 Oct 7;96(7):2190–6. doi: 10.1161/01.cir.96.7.2190. PMID: 9337189. 2. Rodgers CT, Clarke WT, Snyder C, Vaughan JT, Neubauer S, Robson MD. Human cardiac 31P magnetic resonance spectroscopy at 7 Tesla. Magn Reson Med. 2014 Aug;72(2):304–15. doi: 10.1002/mrm.24922. Epub 2013 Sep 4. PMID: 24006267; PMCID: PMC4106879. 3. Ellis J, Valkovič L, Purvis LAB, Clarke WT, Rodgers CT. Reproducibility of human cardiac phosphorus MRS (31 P-MRS) at 7 T. NMR Biomed. 2019 Jun;32(6):e4095. doi: 10.1002/nbm.4095. Epub 2019 Mar 29. PMID: 30924566; PMCID: PMC6546607. 4. Purvis LAB, Clarke WT, Biasiolli L, Valkovič L, Robson MD, et al. OXSA: an open-source magnetic resonance spectroscopy analysis toolbox in MATLAB. PLOS ONE 2017;12(9):e0185356. Conflict of Interest None