[Heart rate and refractoriness of accessory A-V- pathways (author's transl)].

In 20 patients with WPW-syndrome, the effective refractory periods of accessory A-V conduction were measured by programmed atrial stimulation during His-bundle electrography. The effects of basic heart rate on this parameter were evaluated. Three groups of patients were distinguished: A) The effective refractory periods of accessory A-V conduction were clearly longer than the effective refractory periods of the right atrium in 12 patients. In these patients, acceleration of heart rate shortened the effective refractory period of accessory A-V conduction. Refractoriness of accessory A-V conduction was a linear function of cycle length. B) Block of accessory A-V conduction occured at a rather long basic cycle length in three patients. No rate dependency of refractoriness could be evaluated. Methodical problems regarding the determination of effective refractory period of accessory A-V conduction were discussed. The significance of the parameter in question in respect to the trigger mechanism of paroxysmal supraventricular tachycardias (echozone) and the ventricular rate during atrial tachycardias were demonstrated.