Dynamic 31 P-MRI and 31 P-MRS of lower leg muscles in heart failure patients

Impaired oxidative metabolism is one of multi-variate factors leading to exercise intolerance in heart failure patients. The purpose of the study was to demonstrate the use of dynamic 31 P magnetic resonance spectroscopy (MRS) and 31 P magnetic resonance imaging (MRI) techniques to measure PCr resynthesis rate post-exercise as a biomarker for oxidative metabolism in skeletal muscle in HF patients and controls. In this prospective imaging study, we recruited six HF patients and five healthy controls. The imaging protocol included 31 P-MRS, spectrally selective 3D turbo spin echo for 31 P-MRI, and Dixon multi-echo GRE for fat–water imaging on a 3 T clinical MRI scanner. All the subjects were scanned pre-exercise, during plantar flexion exercise, and post-exercise recovery, with two rounds of exercise for 31 P -MRS and 31 P-MRI, respectively. Unpaired t-tests were used to compare 31 P-MRS and 31 P-MRI results between the HF and control cohorts. The results show that PCr resynthesis rate was significantly slower in the HF cohort compared to the controls using 31 P-MRS ( P = 0.0003) and 31 P-MRI ( P = 0.0014). 31 P-MRI showed significant differences between the cohorts in muscle groups (soleus ( P = 0.0018), gastrocnemius lateral ( P = 0.0007) and gastrocnemius medial ( P = 0.0054)). The results from this study suggest that 31 P-MRS/ 31 P-MRI may be used to quantify lower leg muscle oxidative metabolism in HF patients, with 31 P-MRI giving an additional advantage of allowing further localization of oxidative metabolism deficits. Upon further validation, these techniques may serve as a potentially useful clinical imaging biomarker for staging and monitoring therapies in HF-patients.