Comparison of Cardiac Function Between Left Bundle Branch Pacing and Right Ventricular Outflow Tract Septal Pacing in Pacemaker-dependent Patients
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.
The purpose of this study was to compare the changes of cardiac function within 1month in
 pacemaker-dependent patients between LBBP and RVOP. A single-center prospective random
 controlled clinical study was conducted in 60 patients with bradycardia indications. 30
 patients underwent RVOP and 30 patients underwent LBBP. The changes of BNP, echocardiogram
 and speckle-tracking echocardiagraphy, six minutes walk test and quality of life were
 compared between the two groups before and within 1month. The etiology of pacemaker
 implantation included high atrioventricular block, atrial fibrillation with slow arrhythmia.
 Implantation procedures: Left bundle branch pacing was achieved by trans-interventricular
 septum method in the basal ventricular septum and performed by using the Select pacing 3830
 lead(Medtronic Inc, USA) delivered through a fixed sheath(7F C315 HIS, Medtronic Inc, USA).
 During implantation, a unipolar configuration is used for pacing and recording. The delivery
 sheath was inserted through left subclavian vein into atrial side of the tricuspid valve to
 mark His bundle potential under right anterior oblique(20°) fluoroscopic view. As a marker in
 His bundle region, the sheath with the lead tip was further advanced towards the right side
 of the ventricular septum approximately 1.5-2cm, and paced QRS morphology showing left bundle
 branch block(LBBB) at output of 2V/0.4ms. When the sheath with the lead tip screwed to the
 left side of the septum, paced QRS morphology changed from LBBB to right bundle branch
 block(RBBB), a gradual change of the notch morphology("W" waveform) in lead V1 gradually
 shifted and finally disappeared.Another active electrode is implanted in the right
 auricle.Patients with RVOP: The right ventricular pacing lead was positioned in the low
 intervals of right ventricular outflow tract, and atrial active lead was positioned at right
 auricle. BNP was measured routinely before implantation and reexamined on 1 day and 1month
 after pacemaker implantation.Twelve-lead ECG were recorded including QRS duration, QRS
 amplitude and QT interval. Echocardiography data were measured by conventional transthoracic
 echocardiography system including left atrial anteroposterior dimension, left atrial
 transverse dimension, left atrial vertical dimension, e', peak E-wave velocity, peak A-wave
 velocity, E/A, E/e', left atrial ejection fraction (LAEF), left ventricular ejection fraction
 (LVEF), velocity-time integration of aortic blood flow(VTI). Left atrial strain and strain
 rate were measured by speckle-tracking echocardiography(STE).We also measure the six minutes
 walk test and quality of life in all patients before and after implantation in 1month.
Inclusion Criteria:

 Pacemaker-dependent patients who agreed to implant a pacemaker.

 Exclusion Criteria:

 Patients with congenital heart diseases, such as atrial septal defect, ventricular septal
 defect, or rheumatic heart diseases, valvular heart diseases.