Ontogenetic development of the helical heart: concepts and facts.

The structural and functional organization of the ventricular myocardial mass is a controversial matter that cannot be resolved by anatomical studies alone. Therefore, other approaches such as investigations of the ontogenetic development of the ventricular myocardium might help to resolve controversies about its structural and functional organization. It has recently been proposed that the spatial orientation of Torrent-Guasp's ventricular myocardial band model (basal and apical loops) might be the mature morphological correlate of twists and torsions of the embryonic heart loop. In the present contribution, the suggestions made in this concept were analyzed in the light of currently known facts about the development of the embryonic heart. It was found that some of the suggestions made in this concept do not correspond to embryological facts, whereas other suggestions could neither be disproved nor confirmed on the basis of our current knowledge on heart development. The answer to the question as to which of the various models of myocardial fibre organization fits best with the ontogenesis of the myocardial mass awaits future studies. The myocardial units of Torrent-Guasp's myocardial band model are said to have a functional rather than a morphological personality. Future studies on the ontogenetic development of the myocardium, therefore, should comprise not only anatomical analyses of dead specimens but should additionally comprise high resolution in vivo analyses of the development of the spatio-temporal contraction patterns of embryonic and fetal hearts.