Cardiovascular proton magnetic resonance spectroscopy to distinguish between infarct and non-infarct region after ST-segment elevation myocardial infarction

Background Despite advancements, ST-segment elevation myocardial infarction (STEMI) remains a leading cause of mortality, requiring early risk assessment. Cardiovascular magnetic resonance (CMR) provides parameters like infarct size (IS) or ejection fraction (LVEF) to predict remodeling. However, the role of myocardial metabolites in human remodeling after STEMI remains unknown, representing a gap between functional and structural characterisation. 1H-magnetic resonance spectroscopy (1H-MRS) allows non-invasive assessment of triglycerides (TG) and total creatine (CR), a key marker of energy metabolism. Previous studies showed the prognostic value of TG in acute heart failure, but 1H-MRS was primarily limited to whole-septum measurements, restricting precise quantification in infarcted regions. Purpose The objective was to implement myocardial metabolite characterisation using 1H-MRS in both infarct and non-infarct regions in a cohort of patients after left anterior descending (LAD) or right coronary artery (RCA) STEMI Methods Navigator-free, metabolite-cycled 1H-MRS was performed on a 1.5T system in 22 patients with LAD or RCA STEMI (18 males, 59.9 ± 8.2 years). Spectra from infarct (identified by T2-weighted imaging) and adjacent non-infarct zones in the interventricular septum were acquired using an ECG-triggered PRESS sequence. Post-processing used a customised reconstruction pipeline. Ratios of TG-to-water (TG/W) and CR-to-water (CR/W) were calculated. CMR was repeated six months post-STEMI to assess LVEF, end-diastolic volume, and IS. Results Patients undergoing CMR measurements were less severely affected (lower Killip class and IS by enzyme levels) compared to the entire cohort. Spectra showed high quality in both regions with no significant difference in water linewidth. Across all patients, CR/W showed a near-significant decrease (p=0.061) in the infarct zone, while TG/W was non-significantly decreased. In RCA infarctions (n=8), the TG/W decreased significantly (p=0.066). CR/W did not reach significance in subgroups, likely due to sample size, though trends were visible in both territories. Acute TG/W and CR/W did not correlate with baseline LVEDV, LVEF, or IS. However, at six months, patients with an LVEF increase of >=15% had higher acute infarct TG/W levels compared to those without improvement. This effect was most evident in LAD infarctions (p = 0.067 for TG/W in the infarct zone). CR/W showed no correlation with follow-up functional parameters or remodeling. Conclusions Regional 1H-MRS distinguishes metabolic alterations between infarct and non-infarct zones. Lower TG/W and CR/W characterise infarcted tissue. Higher acute infarct TG/W is associated with 6-month LVEF recovery, suggesting 1H-MRS provides incremental prognostic value post-STEMI.