[Second degre Wenckebach phenomenon. Electrocardiographic and clinical study apropos of 10 cases].

Study of atrio-ventricular conduction across the atrio-ventricular node using rapid atrial stimulation revealed a particular kind of block in 10 patients; the characteristics of the Wenckebach phenomenon were associated with a 2/1 block. One P wave was blocked, and the PR interval of the conducting sequence became progressively longer until the cycle was broken by two consecutive blocked P waves. By recording the potentials in the bundle of His, it proved possible to localise the conduction defect to the A/V node in 9 cases. The defect appeared in various clinical forms: atrial tachysystole, incomplete atrio-ventricular block, both chronic and acute, and atrio-ventricular conduction that was apparently normal. Study of the transmission through the node of progressively increasing atrial stimuli showed that there was a strong tendency towards diminishing conductivity which appeared to favour dispersion of the incoming impulses centrally within the node.