Dynamic P-MRI and 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 P magnetic resonance spectroscopy (MRS) and 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 P-MRS, spectrally selective 3D turbo spin echo for 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 P -MRS and P-MRI, respectively. Unpaired t-tests were used to compare P-MRS and 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 P-MRS (P = 0.0003) and P-MRI (P = 0.0014). 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 P-MRS/P-MRI may be used to quantify lower leg muscle oxidative metabolism in HF patients, with 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.