Ultra-high-field 7T phosphorus magnetic resonance spectroscopic imaging (31P-MRSI) mapped the phosphocreatine-to-ATP ratio (PCr/ATP) across six mid-ventricular cardiac segments in 21 participants spanning healthy volunteers, type 2 diabetes, heart failure, and ischemic cardiomyopathy. PCr/ATP dropped dramatically from 1.78 ± 0.21 in healthy hearts to 1.10 ± 0.28 in heart failure (eta² = 0.58, p = 0.005). Crucially, ischemic patients showed PCr/ATP of 0.79 in infarcted segments versus 1.33 in structurally intact remote myocardium — with all three ischemic patients falling below the healthy median — suggesting systemic energetic stress beyond visible damage zones.
This preprint, not yet peer-reviewed, advances a technically demanding but potentially transformative imaging frontier. Standard cardiac MRI reveals structure and gross function; 31P-MRSI adds metabolic granularity that could identify at-risk myocardium before mechanical dysfunction appears. The finding that energetic impairment propagates into remote, structurally preserved tissue in ischemic cardiomyopathy aligns with emerging concepts of cardiac metabolic remodeling as a whole-organ phenomenon, not merely a focal scar problem. For metabolic cardioprotection trials — testing agents like SGLT2 inhibitors, ketone supplements, or mitochondrial modulators — regional PCr/ATP mapping could serve as a far more sensitive endpoint than ejection fraction alone. The primary limitation is sample size: with only 3–5 patients per disease group, effect sizes are exploratory and confidence intervals wide. The measurement quality gradient restricting coupling analysis to septal segments also warrants technical refinement. Larger, gated-acquisition trials are essential before clinical translation.
