Abstract 277: High Consistency in Left Ventricular 31P-MR Spectra in Rats in vivo Allows Follow-up Detection of Small Variations in Energy Status and Early Energy Defects

Abstract

Introduction: Phosphorus magnetic resonance spectroscopy (31P-MRS) makes a unique and valuable contribution to understand how mitochondrial energy supply responds to ATP demand in beating hearts. Changes in PCr/ATP allow detecting energy dysbalance that often predict disease and mortality. However, MR techniques in vivo are challenged by tissue contamination and poor signal-to-noise (S/N) ratio, especially in hearts of rodent models. Methods: Here we optimized acquisition of localized cardiac 31P-MR spectra, obtained with a surface probe at 9.4T in vivo from left ventricle in control and SHR rats. MR spectra (192s) and short-axis cine-MRI frames were obtained during 9-weeks in sinus rhythm and during tachycardia induced by acute injection of isoproterenol (10μg/kg) at week 10. Results: Highly reproducible spectra with low S/N ratio helped demonstrating healthy PCr/ATP despite progressive ventricular hypertrophy in SHR rats. Isoproterenol induced similar tachycardia (425bpm ± 7) but higher drop in PCr/ATP (-17.1% vs. -4.7%, P<0.05) associated with higher recovery time constant (23.9 vs. 7.3 min, P<0.05). Discussion/Conclusion: Our results indicate that SHR rats maintain energy homeostasis during early development of pathology but present a blunted capacity of mitochondrial energy supply to respond to high ATP demand during strong ß-adrenergic activation of the myocardium. The optimization in localized 31P-NMR analysis offer exciting possibilities to better investigate primary precursors detection of cardiac failure in rodent models.