Magnetic resonance imaging for assessment of myocardial function.

It is likely that, as the field progresses, cardiac magnetic resonance imaging (MRI) will become the definitive reference imaging method for evaluation of myocardial function. The first phase of development in the field has emphasized replication and improvement of commonly used methods for analysis of global ventricular pump function, global ventricular mechanics, and regional myocardial performance. Thus, validated MRI methods exist for assessment of ventricular end-diastolic and end-systolic volume and ejection fraction. Similarly, standard methods for evaluation of myocardial mean wall stress can be applied to evaluation of afterload as a determinant of ventricular performance. Regional function of myocardium can be evaluated using either regional endocardial motion or regional wall thickening. In addition, recent development of novel methods for assessment of local myocardial motion by tracking motion at fixed points in the tissue over the cardiac cycle has attracted interest from the cardiovascular research community. These methods, such as radial stripe myocardial tagging and spatial modulation of magnetization, have already provided unique and incisive new information on segmental myocardial performance in normal and diseased hearts in experimental models and in man. The most important limitation of cardiac MRI for assessment of cardiac function continues to be long image acquisition times. The advent of real time methods, with further development, should address this problem.