Cardiac energetics alteration in chronic hypoxia rat model: a non invasive in vivo 31P magnetic resonance spectroscopy experimental study

Background: Energetics alteration plays a key role in the process of myocardial injury in chronic hypoxic diseases (CHD). 31P magnetic resonance spectroscopy (MRS) can investigate alterations in cardiac energetics in vivo. This study was aimed to characterize the potential value of 31P MRS in evaluating cardiac energetics alteration of chronic hypoxia rats (CHR).Methods: Twenty-four CHRs were induced by SU5416 combined with hypoxia, and six rats were raised as control group. 31P MRS was performed weekly and the ratio of concentrations of phosphocreatine (PCr) to adenosine triphosphate (ATP) (PCr/ATP) was obtained. The index of cardiac structure and systolic function parameters, including the right ventricular function (RVEF), right ventricular end-diastolic volume index (RVEDVi), right ventricular end-systolic volume index (RVESVi), the left ventricular function parameters were also measured.Results: The declension of resting cardiac PCr/ATP ratio in CHR was observed at the 1st week, compared to control group (2.90±0.35 vs. 3.31±0.45, p =0.045), while the RVEF，RVEDVi and RVESVi decreased at the 2nd week (p＜0.05). The PCr/ATP ratio displayed a significant correlation with RVEF(r = 0.605, p = 0.001)，RVEDVi and RVESVi (r = -0.661, r = -0.703; p＜0.001).Conclusions: 31P MRS can early detect the cardiac energetics alteration in CHR model before the onset of ventricular dysfunction. The decrease of PCr/ATP ratio likely revealed myocardial injury and cardiac dysfunction.