Comparison of Cardiac Function Between Left Bundle Branch Pacing and Right Ventricular Outflow Tract Septal Pacing in Pacemaker-dependent Patients

Permanent pacemaker implantation is a common method for bradycardia and cardiac conduction dysfunction. With the development of physiological pacing, the optimal location of ventricular pacing site is still improving. Traditional ventricular pacing site at the apex of right ventricle or septum of right ventricular outflow tract（RVOT）, causing iatrogenic left bundle branch block and asynchronous ventricular contraction, leading to cardiac remodeling, pacemaker-mediated cardiomyopathy and congestive cardiac failure. Long-term chronic ventricular pacing can lead to changes in endocardial myocytes and myofibrils and promote fibrosis. Thus, the alternative pacing site, HIS bundle pacing, has been sought later. The safety and feasibility of permanent HIS bundle pacing have been confirmed in patients with various cardiac diseases. However, the shortcomings of high and unstable threshold, long implantation time, low R-wave amplitude and HIS bundle damage during implantation limit the application of HIS pacing especially in patients with infra-Hisian block. Left bundle branch pacing(LBBP) is a new technique evolved from HIS bundle pacing. In 2017, Huang et al\[9\]reported that LBBP was successfully paced using 3830 leads(Medronic Inc. USA). The advantages of narrow QRS duration, low threshold, high R wave amplitude, easy fixation and correction of left bundle branch block made LBBP more widely used in clinic.However, whether left bundle branch pacing is superior to traditional right ventricular outflow tract septal pacing in cardial function is still lack of sufficient evidence. The purpose of this study is aim to using Brain natriuretic peptide(BNP), echocardiography and speckle-tracking echocardiagraphy, six minutes walk test and quality of life to compare the changes of cardiac function within 1 month between LBBP and RVOP in pacemaker-dependent patients.