Objective: To explore the safety and feasibility of left bundle branch area pacing (LBBAP) in children. Methods: This study observed 12 children attempted LBBAP from 2019 to 2021 in our department prospectively. Clinical data, pacing parameters, electrocardiograms, echocardiographic measurements and complications were recorded at implant and during follow-up. Results: The 12 patients aged between 3 and 14ys and weighted from 13 to 48kg. 11 patients were diagnosed with third-degree AVB and 1 patient (case 4) suffered from cardiac dysfunction due to right ventricular apical pacing (RVAP). LBBAP was successfully achieved in all patients with narrow QRS complexes. LVEF of case 4 recovered on the 3rd day after LBBAP. The median of LVEDD Z score of the 12 patients decreased from 1.75 to1.05 3 months after implantation (p<0.05). The median of paced QRS duration was 103ms. The median of pacing threshold, R-wave amplitude and impedance were 0.85V, 15mV and 717Ω respectively and remained stable during follow-up. No complications such as loss of capture, lead dislodgement or septal perforation occurred. Conclusions: LBBAP can be performed safely in children with narrow QRS duration and stable pacing parameters. Cardiac dysfunction caused by long-term RVAP can be corrected by LBBAP quickly.

Objective: This study aimed to evaluate the long-term outcome of patients with PDA associated with UAPA. Methods: Patients diagnosed with PDA associated with UAPA were retrospectively enrolled from January 2005 to June 2019. Clinical data, treatment and follow-up information were evaluated. Results: 11 patients (5 males and 6 females) were diagnosed with PDA associated with UAPA. Percutaneous closure was conducted in 9 patients successfully. The median age was 37 months. The mean diameter of the PDA and occluders were 5.3±1.8mm (range 2-8.1 mm), 11.5±3.9 mm (4-16 mm) respectively. The median in 5 patients with the pulmonary: systemic flow ratio (Qp:Qs) was 1.41(1.28-8.7) and total lung resistance was 12 wood (1.8-13.6) . The mean systolic pulmonary artery pressure was 68.3±19.1mmHg（42-105mmHg). In 5 patients with pre- and post-procedure catheter data, the systolic pulmonary arterial pressure decreased significantly after closure 77.0±20.2 v 58.8±17.5 mmHg (p = 0.024), and so was the mean pulmonary arterial pressure 58.2±14.6 v 39.0±14.1 mmHg (p = 0.18). The pulmonary artery pressure and heart size gradually decreased to normal in 8 patients, and the quality of life was significantly improved. The ratio of lung to systemic circulation pressure in all these patients was less than 0.75. Conclusions: In appropriate patients with PDA associated with UAPA, transcatheter closure of PDA has the potential to improve the pulmonary artery hypertension. The ratio of lung to systemic circulation pressure less than 0.75 may be important reference index for predicting whether the pulmonary artery pressure could be reduced to normal after occlusion.