Potential and limitations of nuclear magnetic resonance for the cardiologist.

One of the fundamental problems in cardiovascular research is concerned with the relation between biochemical energy provision and demand of the myocardium in healthy and diseased states. Until recently most of the available biochemical information was a result of indirect or highly invasive measurements. During the past nine years we have shown that nuclear magnetic resonance spectroscopy is a powerful tool for the study of tissue energetics' and have developed techniques for the study of isolated and in vivo organs in animals2 and more recently in man.3 Nuclear magnetic resonance is observed as a very weak response when chemical substances are placed in a strong uniform magnetic field and are irradiated with weak radiofrequency waves. It arises from the interaction of atomic nuclei with the applied magnetic field and yields detailed information abdtt chemical structures and molecular motions. Only those nuclei that have magnetic properties give rise to signals. For example, when the 1H atom is observed signals mainly from water and fat are obtained and are used for reconstructing spatially resolved images. The clinical applications of nuclear magnetic resonance imaging are reviewed in this issue.4 In our own work we use nuclear magnetic resonance in a different way. If we apply considerably stronger and more homogeneous magnetic fields than those used in imaging signals from individual chemicals can be resolved in the frequency domain. We have mainly concentrated on detecting phosphorus nuclei and are now able to follow various biochemical processes by the use of phosphorus (31P) nmclear magnetic resonance spectroscopy. To appreciate the clinical value of .the method in cardiology we should consider the bioenergetic processes in muscle (Fig. 1). The key role of adenosine triphosphate in providing the energy for work is assured by adequate provisions for maintaining its concentration through three sepa-