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The cardiac conducting system is vital for generating and synchronizing the heartbeat. Beginning with Tawara, Einthoven and other pioneering workers, a wealth of information has been collected over the last 100 years on the histologic, morphologic and physiologic characteristics of specialized cardiac tissues. However, in the last ten years considerable effort has been put into understanding the cellular and molecular mechanisms governing its development. During this latter period, controversies have also arisen as to the nature of the signaling mechanisms involved in induction and patterning of the conducting system, particularly with respect to the pathways functioning in mammals. In this review, we will try to summarize the current state of knowledge in this field and point out some of the remaining questions.

It has been 160 years now since Purkynje published the finding of conduction fibers in the heart in Archiv f. Anatomie u. Physiologie and it has been 166 years since his publication in polish version. Already during Purkynje's life, some anatomists had solved the morphology of these fibers but nobody at that time knew of what great physiological and medical importance this discovery would be for medicine. It was seen as late as in the 20th century and in contemporary times. Purkynje's work indicated the cascade of these discoveries, which were leading in the beginning of the previous century to the formulation of the basic scheme of the conduction system. Purkynje fibers or Purkynje cardiomyocytes are part of the whole complex of the cardiac conduction system which today is classified as specific heart muscle tissue, being responsible for the generation of the heart impulses. From the point of view of ultrastructural composition, the cells of different parts of the cardiac conduction system are partly similar. In contrast to the heart contractile cardiomyocytes, the cells of the cardiac conduction system including Purkynje fibers have a small amount of myofibrils,small mitochondrias, light cytoplasm and a higher glycogen content, but no T-tubular system. They can be detected with some morphological methods. Nevertheless the cells of the conduction system are not completely uniform. They differ in size, number of nexuses-gaps and intercalar discs in individual parts of the conduction system. Nevertheless, these specialized cells work as a whole-unit. Nowadays, the morphology research of all the parts of cardiac conduction system, including Purkynje fibers, is focused on ultrastructural, histochemical and genetical problems. The question is, wheather with future gene/cell therapy disturbances of the conduction system such as arrythmias, can be prevented and cured by replacing the electrical pacemakers with biological ones. If Jan Evangelista Purkynje lived today, he would be surprised but surely delighted with the high degree of research concerning his discovery and its clinical application.