ABSTRACT
Objective:To explore the mechanism of the alternation of RR interval length in atrioventricular reentrant tachycardia (AVRT).Methods:From August 2009 to August 2016, 317 patients with AVRT were treated by radiofrequency catheter ablation in cardiology department of TEDA International Cardiovascular Hospital were analyzed retrospectively.During AVRT, 5 mg of verapamil was given slowly intravenously for 10 min.After administration, the changes of RR interval, AH interval, HV interval and VA interval were observed and the time of changes was also observed.Results:After administration of verapamil, there were 8 patients with RR interval alternation and QRS wave alternation.When RR interval alternation occurred, the difference of AH interval between adjacent heart beats was gradually extended, without AH jump, and the HV interval and VA interval were constant.This phenomenon occurred 6-17 minutes after administration, and the average cycle of tachycardia was 16-42 ms longer than before administration.In 3 patients, RR interval alternation occurred.When the phenomenon disappeared, the difference of AH interval between adjacent heart beats was gradually shortened, there was no AH jump, and the interval between HV and VA was constant until AH interval was equal, the disappearance time was 19-57 min after administration; AVRT was terminated in 5 patients after administration.Conclusion:It can be concluded that the mechanism is due to the frequency dependent decreasing conduction of AH interval in tachycardia, which can not be induced by program stimulation.