[Ventricular response in atrial fibrillation : normal conduction, consequences of conduction disorders and preexcitation syndromes. Therapeutic implications].

Atrial fibrillation is the most common arrhythmia in man. It is characterized by: 1) a rapid and irregular atrial electrical activity, 2) an irregular ventricular response which follows complex laws in the absence of advanced disorder of atrio-ventricular conduction. The study of these laws of complex transformation which govern the ventricular response can be approached by histograms of the RR interval: the shortest interval between two QRS complexes corresponds approximately to the functional refractory period of the atrio-ventricular conduction pathways--the longest interval corresponds to the maximal intranodal hidden conduction in the central part of the node. Depending on the values obtained and the morphological type of the distribution, we can diagnose all degrees of atrio-ventricular conduction disorders. This has great practical significance in patients receiving or about to receive cardiotonics or antiarrhythmics. In the same way, in cases of pre-excitation syndrome, this method can be used to evaluate the refractory period of the accessory pathway and to guide treatment.