Fig. 1.

Noninvasive MRS/CMR protocol for studying cardiac energetics. a (bottom) ³¹P-MRS measurements of [PCr] and [ATP] concentrations in mmol/kg wet-weight using CMR volumetry and a concentration reference, is followed by triple repetition-time saturation-transfer (TRiST) measurements of the CK reaction rate, k_f in s^-1, to obtain the rate of ATP production, or CK flux. The CK flux in mmol/kg/s is converted to Système International (SI) units of W/kg to compare with the cardiac workload based on the free energy of ATP hydrolysis (ΔG_ATP) and the specific gravity (SG). b (top) CMR measurements of left ventricular volume, LV V(t), are combined with blood pressure (BP) cuff measures to determine the instantaneous p(t), average (p_av) and peak (p_p) mechanical power, and the stroke work (SW), potential energy (PE) and total mechanical energy (PVA) in Joules, Watts and W/kg (see Additional file 1). The energetics protocol takes about 50–75 min in total