Résumé
Concealed phenomena in electrocardiography are events which, having no direct effect on the electrocardiogramme, nevertheless change the following sequences giving rise to very unusual appearances. They are diagnosed by deduction. First of all, there is concealed anterograde or retrograde conduction in the AV node, the consequences of which are either a block or the suppression of an escape rhythm or even facilitation of the transmission of activation. Concealed conduction is also possible in the Bundle of His and its branches, explaining the frequency of dependent blocks and aberrant conduction. There is also concealed conduction in accessory pathways. The second form is concealed rhythms: hisian extrasystoles giving rise to pseudo A-V block, and concealed extrasystoles and parasystoles. With temporary pacing of tachycardia, it has finally been possible to describe "visible" concealed phenomena, not on the surface but on the endocavitary electrogramme.