Is MR spectroscopy of the heart ready for humans?

Cardiac magnetic resonance spectroscopy (MRS) is a non-invasive in vivo technique that can be used to measure high-energy phosphate metabolism in heart without harmful radiation or radio-isotopes. Using the property of atomic nuclear spin, this technique provides real-time information on cardiac metabolite composition, including creatine content. Cardiac (31)P MR spectroscopy has shown most promise for the prognosis and treatment of heart failure, but has also been used as a powerful research tool for uncovering energy deficits in cardiomyopathies, ischaemic heart disease and valvular heart disease. Information provided by cardiac (1)H MRS includes myocardial creatine levels, which are decreased in heart failure, and myocardial fat content. Hyperpolarisation is an emerging MRS technique, which allows the (13)C MR signal to be increased many orders of magnitude in studies of substrate metabolism and enzyme kinetics. Cardiac MRS has predominantly been used in research and is not currently ready for routine clinical practice. However, higher MR field strengths, which provide greater signal and spectral resolution, may allow spectroscopy to become more widespread. This article reviews the applications of cardiac MRS, concentrating on the (31)P nucleus, and the current limitations that prevent routine use in research and clinical practice.