Quantitative Evaluation of the First Order Creatine-Kinase Reaction Rate Constant in in vivo Shunted Ovine Heart Treated with Oxandrolone Using Magnetization Transfer 31P Magnetic Resonance Spectroscopy (MT-31P-MRS) and 1H/31P Double-Tuned Surface Coil: a Preliminary Study

ABSTRACT

PURPOSE: Children born with single ventricle physiology demonstrate poor growth rate and suffer from malnutrition, which lead to increased morbidity and mortality in this population. We assume that an anabolic steroid, oxandrolone, will promote growth in these infants by improving myocardial energy utilization. The purpose of this paper is to study the efficacy of oxandrolone on myocardial energy consumption in these infants. MATERIALS AND METHODS: We modeled single ventricle physiology in a lamb by prenatally shunting the aorta to the pulmonary artery and then postnatally, we monitored cardiac energy utilization by quantitatively measuring the first order reaction rate constant, kf of the creatine-kinase reaction in the heart using magnetization transfer 31P magnetic resonance spectroscopy, home built 1H/31P transmit/receive double tuned coil, and transmit/receive switch. We also performed cine MRI to study the structure and dynamic function of the myocardium and the left ventricular chamber. The spectroscopy data were processed using home-developed python software, while cine data were analyzed using Argus software. RESULTS: We quantitatively measured both the first order reaction rate constant and ejection fraction in the control, shunted, and the oxandrolone-treated lambs. Both kf and ejection fraction were found to be more significantly reduced in the shunted lambs compared to the control lambs, and they are increased in oxandrolone-treated lambs. CONCLUSION: Some improvement was observed in both the first order reaction rate constant and ejection fraction for the lamb treated with oxandrolone in our preliminary study.