New Concepts For Molecular And Functional Imaging Of The Heart: Implications For Regenerative Treatments

New advances in the knowledge of myocardial structure and function at genetic, molecular, and microscopic levels bring new opportunities for drug discovery and integrated therapies. The helical ventricular myocardial band is a new concept in our understanding of the functional architecture of the ventricular myocardium. The previous concept of constriction is replaced by the understanding that clockwise and counterclockwise helical motions are necessary to cause the predominant twisting motion. This new model allows for novel understanding of cardiac mechanisms and provides new insights for new treatments such as the restoration or de-novo engineering of heart structures. Recent Fourier analysis of the sequence of ventricular mechanical activation has confirmed a base-to-apex sequence of activation. This is in agreement with recent studies showing the temporal evolution of the three-dimensional strain maps derived from magnetic resonance imaging, which allow mapping of the electromechanical motion of the ventricles. There are several fields in which the impact of these new concepts may be of importance. Imaging online of myocardial fiber dynamics through resonance tensor diffusion imaging, or other imaging means, opens the way to research and the development of more adequate surgical strategies to compensate for cardiac dysfunction. In surgery for heart failure, it seems appropriate to plan surgery in such a way as to spare the helical ventricular anatomy. In cardiac resynchronization, knowledge of the natural sequence of electromechanical ventricular activation should open the way to study the effects of selective stimulation of the band segments on ventricular function, and should provide a rationale for improved ventricular pacing protocols. Coupling cardiac (123)I-metaiodobenzylguanidine (MIBG) studies with functional assessment, taking into account the newly discovered complex mechanics of ventricular activation, should improve the selection of candidates for cardiac resynchronization and the assessment of this treatment. In addition, the eventual site of administration of stem/progenitor cells could be decided on the basis of knowledge of the new model of myocardial fiber distribution. Integrated imaging technologies will bridge the newly discovered structural and functional phenomena with new integrated, targeted, and tailored therapies.