Abstract: Objective:To investigate the electrocardiogram(ECG) of patients with late diastolic premature ventricular contraction in sinus rhythm before and after radiofrequency catheter ablation,and analyze the effects of different bypass prequels on the PJ intervals.Methods:A total of 120 cases with late diastolic premature ventricular contraction in sinus rhythm diagnosed by dynamic electrocardiogram were divided into 10 groups according to the bypass.Twelve lead synchronous ECG were scanned before and after radiofrequency catheter ablation,and the PR interval,PJ interval,QRS interval and δ wave time were measured.Results:Compared with before operation,the postoperative PJ intervals in LPS,RA,RP,RAS,RMS and RPS group significantly prolonged(P< 0.05),and the differences of the postoperative PJ intervals between other groups were not statistically significant(P>0.05).The ECG results showed that the postoperative PR intervals in LL,LPS,RA and RP group significantly prolonged compared with before operation(P< 0.05 to P<0.01),and the differences of the postoperative PR intervals between other groups were not statistically significant(P>0.05).The postoperative QRS intervals in LPS,RL,RP,RAS,RMS and RPS groups were longer than those before operation(P<0.05 to P<0.01),and the differences of the postoperative GRS intervals between other groups were not statistically significant(P>0.05).The differences of the δ wave times in all groups before operation were not statistically significant(P>0.05).Conclusions:The PJ interval shortening of ECG has important clinical value between contraction in sinus rhythm and intermittent preexcitation syndrome,which is worthy of promotion in primary hospital,and helpful for the ECG diagnosis and differential diagnosis of late diastolic ventricular premature contraction in sinus rhythm.