Objective To investigate the efficacy of permanent left ventricular epicardial pacing through left lateral thoracotomy in children with complete atrioventricular block (CAVB)or complete left bundle branch block (CLBBB)as well as its effects on heart synchronization.Methods Permanent left ventricular epicardial pacemakers were implanted through left lateral thoracotomy in 26 children with CAVB or CLBBB in Heart Center,the First Affiliated Hospital of Tsinghua University.These children aged (2.3 ±2.1 )years old (1 month -9 years old),weight (1 1 .2 ± 5.8)kg (5 -32 kg),among them 1 5 cases were male and 1 1 cases were female.Among the 26 patients,24 patients had CAVB and 2 patients had dilated cardiomyopathy secondary to CLBBB.Fifteen children who visited the Pediatrics Department for acute upper respiratory tract infection were chosen as control group.The efficacy of left ventricular epi-cardial pacemakers was analyzed and its effects on heart synchronization were observed by using tissue Doppler imaging (TDI).Results Implantations of pacemakers were successfully conducted in all the 26 patients with no complications associated with operations.Left atrial and ventricular dual chamber epicardial pacemakers were implanted in 21 patients and left ventricular single chamber epicardial pacemakers were implanted in 5 patients.Within the follow -up period of (28.2 ±1 5.1 )months (1 month -51 months),atrial and ventricular leads were 1 00% effective.No significant diffe-rence was found in atrial electrode sensing,ventricular electrode threshold and ventricular electrode impedance com-pared with those during implantation(P >0.05).For the 6 patients with preoperative cardiac insufficiency,their left ventricular diastolic diameters decreased from (48.50 ±1 1 .1 0)mm to (40.67 ±6.40)mm after operation,and the difference was significant (t =2.96,P =0.030);but left ventricular ejection fraction increased from 0.27 ±0.08 to 0.53 ±0.08 after operation,and the difference was significant (t =-5.02,P =0.004).Two patients with right ven-tricular pacing developed pacemaker syndrome and were switched to left ventricular epicardial pacing.Their cardiac function returned to normal 1 .5 and 2.0 years later,respectively.Fifteen patients received evaluation of heart synchroni-zation by TDI.No significant difference was found in LVEF,septal -to -lateral wall motion delay,septal -to -posterior wall motion delay and standard deviation of Standard deviation of the peak tissue velocity between these 2 groups(all P >0.05).Conclusions For children requiring epicardial pacing,left ventricular epicardial pacing is safe and effec-tive,which can protect left ventricular systolic synchronization,prevent or reverse the pacemaker syndrome.

AIM: To study the chronological pharmacokinetic differences of melatonin (MEL) in non-dipper spontaneously hypertensive rats (SHR). METHODS: The HPLC detection method of MEL was established, and the specificity, precision, recovery rate and stability of the method were examined. Twelve male SD rats were divided into two groups, and a single dose of MEL (20 mg/kg) was given intragastrically at either 08:00 or 20:00, respectively. Plasma samples were collected at 0, 5, 10, 15, 20, 30, 40, 60, 90, 120, 240, 360 min after drug administration, and the plasma MEL concentration was determined by fluorescence HPLC. RESULTS: The specificity, precision, recovery rate and stability of the MEL detection method established in this study were in line with the requirements of the biological analysis method guidelines, proving that the method was mature and reliable. After MEL was administered at 08:00, the T