LAUSR

Creatine (Cr) is an essential metabolite in the creatine kinase reaction that plays a critical role in maintaining normal cardiac function. Chemical exchange saturation transfer (CEST) MRI offers a novel way to map myocardium Cr. This study aims to investigate the dynamic alteration in myocardium Cr during acute infarction using CEST MRI, which may facilitate the understanding of heart remodeling mechanism at the molecular level. Seven adult Bama pigs underwent cardiac cine, Cr CEST, and late gadolinium enhanced T1 -weighted imaging three and fourteen days after myocardium infarction induction on a 3T scanner. Cardiac structural and functional indices, including myocardium mass (MM), end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and ejection fraction (EF), were measured from cines. Infarct angle was determined from LGE T1 w images, based on which myocardium was classified into infarct, adjacent and remote regions. Cr-weighted CEST signal was quantified from a three-pool Lorentzian fitting model and measured within each region and the entire myocardium. Student's t-test was conducted to evaluate any significant differences in measurements between the two time points. Correlation was assessed with Pearson correlation. P values <0.05 were considered statistically significant. Over the studied period, MM, EDV, and ESV did not alter significantly (P>0.05), whereas significant increase of SV and EF and decrease of infarct angle were observed (P<0.05). Meanwhile, Cr-weighted CEST signal elevated significantly at day 14 compared to day 3 in the infarct (10.00±1.28% vs. 6.91±1.54%, P<0.01), adjacent (11.17±2.00% vs. 8.01±1.58%, P = 0.01), and entire myocardium (11.03±1.36% vs. 8.19±1.28%, P<0.01). Moderately negative correlations were shown between the infarct angle and Cr-weighted CEST signals in the infarct (r = -0.80, P<0.001), adjacent (r = -0.58, P=0.03), and entire myocardium (r = -0.76, P<0.01). In conclusion, the dynamic increase of myocardium Cr during acute infarction may interact with cardiac structural and functional recovery. The study provides supplementary insights of heart remodeling process from the metabolic aspect.