Clinical Efficacy of Bachmann Bundle Pacing on New-Onset Atrial Fibrillation in Patients With Cardiac Insufficiency
Phase: NA
Conditions: Heart Failure, Atrial Fibrillation (AF), Cardiac Insufficiency
Sponsor: Fu Wai Hospital, Beijing, China

Clinical Efficacy Study of Bachmann Bundle Pacing in Improving New-
Onset Atrial Fibrillation in Patients with Cardiac Insufficiency 
Study Protocol 
Version No.: V2.0 
Version Date: 30 January 2026 
Study Sponsor: Investigator-Initiated Clinical Study 
Sponsor (if applicable): Fuwai Hospital, Chinese Academy of Medical 
Sciences 
Statistical Unit (if applicable): Fuwai Hospital, Chinese Academy of 
Medical Sciences 
 
 

1 Study Overview/Background/Rationale 
Chronic heart failure (HF) is one of the most common cardiovascular 
diseases with a poor prognosis at present and in the future. For specific 
types of HF patients, cardiac resynchronization therapy (CRT) or 
implantable cardioverter-defibrillator (ICD) can effectively improve 
cardiac function and prevent sudden cardiac death. Atrial fibrillation (AF) 
is the most common arrhythmia comorbid with HF, and the two conditions 
often coexist, interact synergistically, and cause each other. According to 
the Framingham Heart Study, more than half of patients with new-onset 
HF have comorbid AF, and more than one-third of patients with new-onset 
AF suffer from HF. The risk of death is significantly higher when the two 
conditions coexist. Epidemiological data show that the cumulative 
incidence of AF after pacemaker implantation is as high as 30-40%, which 
is significantly higher than that in the general population without 
pacemaker implantation. Different pacing modes and sites may have 
different impacts on the incidence of post-operative AF. 
Traditional atrial pacing involves placing the atrial electrode in the right 
atrial appendage (RAA). Due to its anatomical characteristics, the RAA 
offers reliability and stability for electrode lead implantation, making it a 
commonly used pacing site in clinical practice. However, RAA pacing 
prolongs interatrial conduction, leads to asynchronous atrial contraction 
and hemodynamic changes, and is prone to inducing AF, which is a non-

physiological pacing method. Studies have indicated that the incidence of 
new-onset AF in patients with sinus bradycardia receiving RAA pacing is 
as high as 30-40%. How to prevent new-onset AF in chronic HF patients 
undergoing CRT or ICD therapy has long been a major clinical challenge. 
The Bachmann bundle is currently recognized as the most physiological 
pacing site within the atria. Implanting a pacing electrode in the Bachmann 
bundle region not only ensures stable pacing parameters but also results in 
a narrower P wave compared with the intrinsic sinus rhythm and traditional 
RAA pacing, achieving synchronous activation of the left and right atria. 
A study by Bailin et al. demonstrated that Bachmann bundle pacing can 
reduce the relative risk of paroxysmal AF progressing to persistent AF. 
Another retrospective study comparing the effects of traditional atrial 
pacing (including RAA pacing and right interatrial septal pacing) and 
Bachmann bundle pacing on AF/atrial tachycardia (AT) showed that 
patients receiving Bachmann bundle pacing had a significantly lower 
AF/AT burden than those receiving traditional atrial pacing (P<0.001). 
During long-term follow-up, the atrial arrhythmia burden in patients with 
Bachmann bundle pacing was lower than that in the traditional atrial pacing 
group (P<0.05), and the risk of AF/AT recurrence and new-onset AF/AT in 
the Bachmann bundle pacing group was also lower than that in the 
traditional atrial pacing group (P<0.01). 
Based on these findings, our research team hypothesizes that Bachmann 

bundle pacing helps reduce the risk of new-onset AF and related adverse 
HF events in HF patients undergoing CRT/left bundle branch pacing 
(LBBP) or ICD therapy. However, such studies are still scarce both 
domestically and internationally. 
Our research team has long been engaged in the field of physiological 
pacing, and the relevant preliminary research results provide key support 
for this study entitled "Clinical Efficacy of Bachmann Bundle Pacing in 
Improving New-Onset Atrial Fibrillation in Patients with Cardiac 
Insufficiency". The team has published numerous research articles 
focusing on physiological pacing, which corely confirmed that left bundle 
branch area pacing can effectively reduce the incidence of new-onset AF 
in patients compared with traditional right ventricular pacing. Derived 
from the core logic that "physiological pacing can optimize cardiac 
electrophysiological conduction and reduce the risk of arrhythmias", this 
conclusion provides direct efficacy-related evidence for the study 
hypothesis that "Bachmann bundle pacing (a nearly physiological atrial 
pacing site) can reduce the risk of new-onset AF in HF patients", verifying 
the application value of physiological pacing technology in the prevention 
of AF. 
Meanwhile, the team's ongoing "Randomized Controlled Study on the 
Clinical Efficacy of LBBP-CRT and BiVP-CRT (LBBP-RESYNC Study)", 
the world's first multicenter, prospective, head-to-head comparative study 

independently completed by Chinese scholars, has confirmed that LBBP-
CRT can improve left ventricular function and promote left ventricular 
reverse remodeling more significantly than traditional BiVP-CRT, 
providing a novel strategy for CRT therapy in patients with end-stage HF. 
This study not only accumulated experience in the design of clinical studies 
on physiological pacing (such as randomized controlled framework, multi-
dimensional efficacy evaluation), technical operation specifications and 
data quality control methods for the team, but also further consolidated the 
theoretical basis of "physiological pacing can improve the prognosis of HF 
patients" from the perspective of "physiological pacing optimizes cardiac 
structure and function". It forms a technical logical response with the 
exploration of the atrial-level efficacy of Bachmann bundle pacing in this 
study, providing a solid preliminary guarantee for the smooth 
implementation of the study and the reliability of the conclusions. 
2 Study Objectives 
Chronic HF and AF are two highly prevalent diseases in the cardiovascular 
field, and they often form a "vicious circle": in HF patients, decreased left 
ventricular function leads to left atrial structural remodeling and 
electrophysiological disorders, which are more likely to induce AF; in turn, 
AF episodes further result in the loss of atrial booster pump function and 
further impairment of ventricular pump function, significantly increasing 
the hospitalization rate, stroke incidence and all-cause mortality in HF 

patients. With the continuous growth in the number of patients with chronic 
HF, the risk of new-onset AF is also rising. At the same time, adverse 
events caused by AF episodes, such as stroke and exacerbation of HF, 
further increase the consumption of medical resources and impose a heavy 
burden on the social medical system. Therefore, preventing AF in patients 
with chronic heart failure is an important clinical challenge that must be 
faced in the cardiovascular field at present and in the future. 
At present, clinical treatment for preventing AF in patients with chronic 
heart failure still faces many difficulties. Both the limitations of drug 
intervention and the deficiencies of traditional pacing technology highlight 
the important clinical challenge of this field at present and in the future. 
There are three internodal tracts connecting the sinoatrial node and the 
atrioventricular node. The interatrial tract (Bachmann bundle) branching 
from the anterior internodal tract can conduct electrical impulses to the left 
atrium. Therefore, the Bachmann bundle is an important component of the 
cardiac conduction system, mainly located in the myocardial tissue at the 
top of the right atrium and extending to the upper part of the left atrium. It 
ensures the coordinated contraction of the left and right atria by rapidly 
conducting electrical signals generated by the sinoatrial node to the left 
atrium, and is a key structure for maintaining normal cardiac rhythm. 
The emergence of Bachmann bundle pacing technology may become a safe, 
effective, low-cost and promotable pacing technology for preventing new-

onset AF without increasing the cost of pacing therapy. Therefore, 
exploring whether Bachmann bundle pacing technology can prevent or 
reduce the risk of new-onset AF in chronic HF patients undergoing 
CRT/LBBP or ICD therapy, thereby improving the prognosis and reducing 
related adverse events such as HF rehospitalization and stroke, has 
important clinical significance. 
This study intends to explore the clinical efficacy of Bachmann bundle 
pacing technology in reducing new-onset AF and improving cardiac 
function and related adverse events in HF patients undergoing CRT or ICD 
therapy through a multicenter, randomized controlled study. By comparing 
and analyzing whether Bachmann bundle pacing is superior to traditional 
right atrial appendage pacing in its effects on new-onset AF and cardiac 
function in HF patients undergoing CRT/LBBP or ICD therapy, this study 
aims to explore a new atrial pacing treatment strategy for chronic HF 
patients and provide important evidence-based medical evidence for the 
improvement of clinical outcomes in HF patients undergoing CRT or ICD 
therapy with the new Bachmann bundle pacing technology. 
3 Study Methods 
3.1 Study Design 
This study is designed as a multicenter, prospective, assessor-blinded, 
randomized controlled clinical trial. The study subjects are sinus rhythm 
HF patients with indications for CRT/LBBP or ICD implantation and no 

previous history of AF. Patients will be randomly assigned to the 
Bachmann bundle pacing group or the traditional atrial pacing group before 
surgery, and followed up at regular intervals of 3-6 months after surgery. 
The primary study endpoint is the occurrence of new-onset AF during the 
12-month follow-up after atrial electrode implantation. By comparing and 
analyzing the clinical efficacy of Bachmann bundle pacing group and 
traditional atrial pacing group on new-onset AF in HF patients undergoing 
CRT/LBBP or ICD therapy, the study aims to explore whether Bachmann 
bundle pacing is superior to traditional atrial pacing in its effects on cardiac 
function in patients with chronic cardiac insufficiency. 
This study adopts an assessor-blinded design, i.e., "blinding is applied to 
outcome assessors and data statisticians, but not to the operating surgeons". 
The reason for not blinding the surgeons is that there are significant 
differences between Bachmann bundle pacing and traditional atrial pacing 
in electrode implantation sites and intraoperative localization methods 
(requiring identification of Bachmann bundle potentials), and surgeons 
need to be clearly aware of the grouping to complete the surgical operation. 
However, blinding the outcome assessors can minimize bias to the greatest 
extent. The specific blinding measures are as follows: 
1. Pacemaker programmers, electrocardiogram (ECG) and Holter 
analysts (core outcome measure assessment) 
1.1 Blinded subjects: Full-time physicians in the hospital's ECG 

department 
(responsible 
for 
analyzing 
pacemaker 
programming 
parameters, 12-lead ECG P-wave parameters, and 24-hour Holter 
arrhythmia events). 
1.2 Implementation measures: 
a) During pacemaker programming, ECG and Holter recording, the device 
number is only associated with the patient's screening number, and the 
grouping information is not displayed; 
b) The analysis report only describes "P-wave duration/amplitude during 
paced rhythm" and "type of atrial events (e.g., AF episodes)", without 
mentioning "Bachmann bundle pacing" or "traditional pacing"; 
c) If pacing-related problems requiring confirmation are found in the 
analysis (e.g., abnormal pacing threshold), communication with the study 
coordinator is only conducted through the screening number, without 
inquiring about grouping information. 
2. Echocardiographic assessors (cardiac function measure assessment) 
2.1 Blinded subjects: 3 senior echocardiography experts responsible for 
measuring echocardiographic related parameters. 
2.2 Implementation measures: 
a) During echocardiographic examination, the examining technician only 
records the patient's screening number and does not label the grouping 
information; 
b) When storing echocardiographic reports and images, fields related to 

"pacing mode" (e.g., description of electrode implantation site) are 
concealed, and only basic patient information (screening number, 
examination date) is retained; 
c) When reviewing images, experts from the core echocardiographic 
laboratory only obtain de-identified images and reports without grouping 
information, complete the measurement of indicators independently, and 
enter the measurement results into a special blinded database, with no 
communication with the study execution team before statistical analysis. 
3. Statistical analysts (data processing and result analysis) 
3.1 Blinded subjects: Independent statistical team (responsible for data 
entry, verification and statistical analysis). 
3.2 Implementation measures: 
a) During the data entry stage, "group code substitution" is adopted, with 
the "Bachmann bundle pacing group" labeled as "Group A" and the 
"traditional atrial pacing group" labeled as "Group B". Statisticians only 
have access to the codes and do not know the actual grouping 
corresponding to the codes; 
b) After the completion of statistical analysis, a "blinded analysis report" 
(presenting results with Group A/B) is issued first. After the research team 
confirms no data questions and completes data locking, the statistical 
center will unblind the data and generate the final analysis report 
corresponding to the actual grouping. 

4. Adverse event assessors (safety outcome assessment) 
4.1 Blinded subjects: Adverse event assessment experts designated by the 
hospital's clinical research ethics committee (responsible for judging 
whether complications are related to pacing mode). 
4.2 Implementation measures: 
a) In the adverse event report form, only "type of event (e.g., lead 
displacement, pericardial effusion)", "occurrence time" and "treatment 
measures" are recorded, with pacing mode information concealed; 
b) When conducting assessments, experts independently judge the 
correlation between events and treatment based on de-identified report 
forms without grouping information and original medical records (with the 
description of pacing site in surgical records concealed), and submit the 
assessment results directly to the ethics committee without feedback to the 
study execution team. 
5. Blinding maintenance and unblinding rules 
5.1 Blinding maintenance: 
a) All study data with de-identified grouping information (e.g., 
echocardiographic images, ECGs, case report forms) are labeled with a 
"blinded" identifier, stored in a special encrypted folder, and only 
authorized blinded subjects have access; 
b) In project meetings held during the study, surgeons and follow-up 
physicians are prohibited from disclosing patient grouping information to 

outcome assessors and statisticians; if an "unexpected unblinding" occurs 
(e.g., an assessor accidentally learns the grouping), the unblinding time, 
reason and involved patients must be recorded immediately. The data of 
these patients must be marked separately in the analysis, and sensitivity 
analysis must be performed if necessary. 
5.2 Unblinding rules: 
a) Unblinding time: Unblinding will be witnessed by the study principal 
investigator (PI, Professor Fan Xiaohan), independent statistician and 
representative of the ethics committee after all patients complete the 12-
month follow-up and all data are entered and locked after verification; 
b) Unblinding sequence: First, unblind the "correspondence between group 
codes and actual grouping", and then improve the final statistical report 
based on the unblinding results; if a serious adverse event occurs during 
the study and emergency judgment on its correlation with treatment is 
required, an "emergency unblinding" can be applied for, but it must be 
approved by the ethics committee, the reason for unblinding must be 
recorded, and only the relevant judging personnel are informed. The 
blinded state will be restored after the judgment is completed. 
This study adopts a stratified block randomization design, with "type of 
implanted device" as the stratification factor, dividing the study subjects 
into the "CRT/LBBP implantation subgroup" and the "ICD implantation 
subgroup". The stratification is based on the differences in indications, 

implantation procedures and patients' basic conditions of different devices 
in clinical treatment. Stratified randomization can ensure the balance of 
baseline characteristics between the Bachmann bundle pacing group and 
the traditional atrial pacing group in each subgroup, reduce the 
confounding effect of device type differences on the study results, and 
make the comparison of efficacy between groups more targeted and 
reliable. Setting blocks can ensure the balance of the number of patients 
between the experimental group and the control group. The block size is 
determined by the independent statistical team according to the actual 
situation. The specific measures of the randomization scheme are as 
follows: 
1. Enrollment confirmation and stratification: After the patient 
completes the screening period assessment (meeting the 
inclusion/exclusion criteria and signing the informed consent form), 
the study coordinator selects the corresponding stratified subgroup 
(CRT/LBBP or ICD) in the randomization system according to the 
finally determined "type of implanted device". 
2. Allocation execution: Using a central randomization system, after 
the study coordinator enters the basic patient information (e.g., 
initials, screening number) into the system, the system automatically 
generates a unique random allocation number and immediately feeds 
back the "allocated group" (Bachmann bundle pacing group or RAA 

pacing group). This process is irreversible and fully traceable. 
3. Surgical connection: The study coordinator informs the surgeon of 
the allocation result and performs electrode implantation according 
to the allocated group; if the attempt of Bachmann bundle pacing 
fails, it will be converted to traditional atrial pacing according to the 
protocol. The reason for failure (e.g., anatomical variation, inability 
to place the electrode) must be recorded in detail in the "surgical 
record form" and included in the intention-to-treat (ITT) analysis. 
3.2 Study Subjects 
3.2.1 Definition of Inclusion and Exclusion Criteria for All Study 
Populations 
Inclusion Criteria 
1. Aged 18 to 70 years; 
2. Diagnosed with chronic cardiac insufficiency in accordance with 
current guidelines based on symptoms and signs, and receiving 
guideline-directed medical therapy (GDMT) for at least 3 months; 
3. With indications for CRT/LBBP or ICD implantation and an 
expected atrial pacing percentage of more than 20%, including: ① 
Symptomatic HF patients with sinus rhythm, QRS duration >120 ms, 
left bundle branch block (LBBB) and LVEF ≤35%; ② Symptomatic 
HF patients with sinus rhythm, QRS duration ≥150 ms, non-LBBB 
and LVEF ≤35%; ③ Symptomatic HF patients with sinus rhythm, 

QRS duration >120 ms, LBBB and LVEF of 36%-50%; ④ 
Symptomatic HF patients with an expected ventricular pacing 
percentage >20% and LVEF ≤50%; ⑤ Patients with symptomatic 
HF and LVEF ≤50% who require ICD implantation for primary or 
secondary prevention of sudden death, and have indications for atrial 
pacing due to sinus bradycardia or an expected atrial pacing 
percentage of more than 20%; ⑥ Patients with pacing-induced HF 
requiring upgrade therapy, in sinus rhythm and undergoing 
reimplantation of atrial electrodes or reimplantation after removal of 
the original atrial electrodes. 
4. Signed the study informed consent form. 
Exclusion Criteria 
1. Expected survival time of less than 12 months; 
2. Post mechanical tricuspid valve replacement or congenital heart 
disease (including dextrocardia, transposition of the great arteries, 
persistent left superior vena cava); 
3. Previous history of AF; 
4. Previous cardiac surgery or need for surgical treatment due to severe 
structural heart disease within 1 year; 
5. Pregnancy, planned pregnancy or heart transplantation; 
6. Refusal of the patient to participate. 
3.2.2 Grouping of Study Subjects 

This study adopts a stratified block randomization design, with "type of 
implanted device" as the stratification factor, dividing the study subjects 
into the "CRT/LBBP implantation subgroup" and the "ICD implantation 
subgroup". The stratification is based on the differences in indications, 
implantation procedures and patients' basic conditions of different devices 
in clinical treatment. Stratified randomization can ensure the balance of 
baseline characteristics between the Bachmann bundle pacing group and 
the traditional atrial pacing group in each subgroup, reduce the 
confounding effect of device type differences on the study results, and 
make the comparison of efficacy between groups more targeted and 
reliable. Setting blocks can ensure the balance of the number of patients 
between the experimental group and the control group. The block size is 
determined by the independent statistical team according to the actual 
situation. 
3.2.3 Study Procedures and Interventions 
The study is carried out in three stages, covering enrollment, follow-up and 
data processing, with strict quality control and blinded design throughout 
the process. 
1. Preparatory stage 
1.1 Protocol approval: Complete study registration and ethical committee 
review to ensure compliance with the Declaration of Helsinki and medical 
ethical norms. 

1.2 Personnel training: Conduct special training for surgeons, follow-up 
personnel and data statisticians to unify surgical operation specifications, 
endpoint definitions (e.g., diagnostic criteria for new-onset AF) and data 
collection standards. 
1.3 Pilot study: Conduct pre-collection and pre-analysis of data from a 
small number of cases, correct data collection problems, and initiate formal 
enrollment after confirming the feasibility of the process. 
2. Patient enrollment and intervention implementation stage 
2.1 Patient screening: Screen patients aged 18-70 years with a diagnosis of 
chronic cardiac insufficiency, indications for CRT/LBBP or ICD 
implantation and no history of AF in accordance with the 
inclusion/exclusion criteria. 
2.2 Random grouping: Adopt a stratified block randomization design with 
"type of implanted device" (CRT/LBBP or ICD) as the stratification factor, 
and divide the patients into the Bachmann bundle pacing group (55 cases) 
and the traditional atrial pacing group (55 cases) at a 1:1 ratio. The 
allocation results are generated through a central randomization system. 
2.3 Surgical intervention: The surgeon performs pacing electrode 
implantation according to the grouping. The Bachmann bundle pacing 
group needs to localize the Bachmann bundle region and record the 
intracavitary ECG, while the traditional group undergoes implantation in 
the right atrial appendage; if the attempt of Bachmann bundle pacing fails, 

it is immediately converted to traditional atrial pacing, and the reason for 
failure is recorded. 
2.4 Baseline data collection: Collect patient demographic information, 
medical history, cardiovascular medication, NYHA classification, 
echocardiographic parameters (atrial size, LVEDD, etc.), 24-hour Holter, 
NT-proBNP 
and 
pacing-related 
parameters 
(threshold, 
sensing, 
impedance). 
3. Follow-up and data processing stage 
3.1 Regular follow-up: Conduct follow-up at 1 week, 3 months, 6 months, 
9 months and 12 months after surgery to collect information on survival 
status, 
clinical 
symptoms, 
medication 
status, 
ECG, 
Holter, 
echocardiography, pacemaker parameters and adverse events (e.g., HF 
rehospitalization, death); additional assessments are performed at any time 
when patients develop symptoms. 
3.2 Data management: Collect data using standardized case report forms 
(CRFs) and an electronic data capture (EDC) system. Establish a special 
team for data desensitization, storage and quality control. The core 
echocardiographic laboratory adopts blinded image review to analyze 
cardiac function indicators. 
Statistical analysis: Data are processed in accordance with the ITT 
principle. The primary endpoint (new-onset AF within 12 months) and 
secondary endpoints (e.g., surgical success rate, changes in cardiac 

function) are analyzed using t-test, chi-square test, Kaplan-Meier method, 
etc. Subgroup analysis is performed according to the "type of implanted 
device" to verify the reliability of the results. 
Interventions: The core of the intervention is the comparison of two atrial 
pacing modes, focusing on technical operation and efficacy and safety 
assessment. 
1. Experimental group: Bachmann bundle pacing 
1.1 Operation method: Intraoperatively identify the Bachmann bundle 
region through anatomical localization and intracavitary ECG, and implant 
the pacing electrode in this region to ensure characteristic ECG 
manifestations during pacing (e.g., positive P waves in leads I, II, III and 
aVF, biphasic or negative P waves in lead V1, and narrowed P wave 
duration compared with sinus rhythm). 
1.2 Parameter monitoring: Record pacing threshold, sensing and 
impedance intraoperatively, and regularly program the pacemaker during 
post-operative follow-up to adjust parameters for maintaining stable 
pacing function. 
1.3 Failure contingency plan: If the electrode cannot be accurately 
localized or the pacing parameters fail to meet the standards, immediately 
convert to traditional atrial pacing to ensure effective treatment for the 
patient. 
2. Control group: Traditional atrial pacing 

1.1 Operation method: Implant the pacing electrode in the right atrial 
appendage (RAA), a routine clinical operation that relies on the anatomical 
convenience of the site to ensure electrode stability. 
1.2 Parameter monitoring: Same as the experimental group, monitor pacing 
threshold, sensing, impedance and other parameters intraoperatively and 
during post-operative follow-up to ensure normal pacing function. 
General interventions and follow-up management 
• Basic therapy: Patients in both groups continue to receive GDMT 
for at least 3 months, and medication adjustments are recorded 
during follow-up. 
• Safety monitoring: Track perioperative complications (e.g., lead 
displacement, pericardial effusion) and adverse events within 12 
months after surgery (all-cause death, HF rehospitalization, stroke) 
throughout the study. Experts designated by the ethics committee 
conduct blinded assessments of the correlation between events and 
pacing mode. 
3.2.4 Follow-up Methods 
All study subjects will be enrolled within 1 year, and various observation 
indicators will be followed up according to the following schedule: 
 
Data Collection 
Criteria 
Screening 
Visit 
Baseline 
Month 3 
Month 6 
Month 9 
1 Year 
Unscheduled 
Inclusion/Exclusion 
Criteria 
√ 
 
 
 
 

Data Collection 
Criteria 
Screening 
Visit 
Baseline 
Month 3 
Month 6 
Month 9 
1 Year 
Unscheduled 
Patient 
Demographic 
Information, 
Medical History 
√ 
 
 
 
 
Cardiovascular 
Medication 
√ 
√ 
√ 
√ 
√ 
√ 
√ 
Physical 
Examination 
(Including NYHA 
Classification) 
√ 
√ 
√ 
√ 
√ 
√ 
√ 
Routine 
Echocardiography  
√ 
 
 
√ 
 
√ 
√ 
24-hour Holter 
Examination 
√ 
 
√ 
√ 
√ 
√ 
√ 
Posteroanterior 
Chest X-ray 
√ 
√ 
 
√ 
√ 
NT-proBNP 
√ 
 
√ 
 
√ 
√ 
Implantation Data 
(Including 
Implantation Time, 
Fluoroscopy Time) 
√ 
 
 
 
Fluoroscopic 
Images of 
Pacemaker Lead 
Implantation (RAO 
30°, LAO 45°) 
√ 
 
 
 
12-lead ECG and 
EGM in Intrinsic 
Rhythm 
√ 
√ 
 
 
 
Information on 
Pacemaker and 
Electrode Lead 
Type 
√ 
 
 
 
12-lead ECG and 
EGM in Paced 
Rhythm 
√ 
√ 
√ 
√ 
√ 
√ 
Pacemaker Pacing, 
Sensing, 
Impedance and 
√ 
√ 
√ 
√ 
√ 
√ 

Data Collection 
Criteria 
Screening 
Visit 
Baseline 
Month 3 
Month 6 
Month 9 
1 Year 
Unscheduled 
Battery Life Data, 
Atrial/Ventricular 
Pacing Percentage, 
Atrial High-Rate 
Events, etc. 
Recent or New-
Onset Arrhythmia 
Events 
√ 
√ 
√ 
√ 
√ 
√ 
√ 
Recent 
Cardiovascular 
Surgery and 
Operative Events 
√ 
 
√ 
√ 
√ 
√ 
√ 
All-Cause Death 
 
√ 
√ 
√ 
√ 
√ 
Newly Diagnosed 
HF Requiring 
Diuretic or Device 
Therapy 
 
√ 
√ 
√ 
√ 
√ 
Pacing-Related 
Serious Adverse 
Events 
√ 
√ 
√ 
√ 
√ 
√ 
Study Protocol 
Deviation Report 
(if applicable) 
√ 
 
 
 
 
Note: The time window for each follow-up point is the preset core time 
point ± 30 days. 
3.3 Selection and Confirmation of Study or Outcome Measures 
3.3.1 Primary Study Endpoint 
Occurrence of new-onset AF during the 12-month follow-up after 
implantation of CRT/LBBP or ICD devices.  
 
For the primary endpoint of incidence of new-onset atrial fibrillation at 12 
months post-implantation, in addition to the overall population analysis, a 

pre-specified stratified subgroup analysis by type of implanted device will 
be performed as a confirmatory analysis of the primary efficacy. 
 
3.3.2 Secondary Study Endpoints 
1. Time to the occurrence of new-onset AF during the follow-up after 
implantation of CRT/LBBP or ICD devices; 
2. Immediate surgical success rate of Bachmann bundle pacing and 
incidence of perioperative complications in the two pacing groups; 
3. Changes in echocardiographic parameters such as atrial size, 
valvular regurgitation severity, LVEDD and LVESV assessed by 
echocardiography in the two groups at 12 months of follow-up 
compared with baseline; 
4. Changes in NYHA classification, 6-minute walk distance and NT-
ProBNP level in the two groups at 12 months of follow-up compared 
with baseline; 
5. Comparison of ECG P-wave duration, P-wave amplitude, P-wave 
vector, interatrial block, ventricular pacing threshold, sensing and 
impedance between the two groups at baseline and 12 months of 
follow-up; 
6. Surgical complications in the two groups within 12 months of 
follow-up; 
7. HF rehospitalization events, all-cause death events or stroke events 

in the two groups within 12 months of follow-up. 
 
All secondary endpoints (including time to new-onset atrial fibrillation, 
surgical success rate, changes in cardiac function, incidence of adverse 
events, etc.) will also undergo pre-specified subgroup analysis 
comparing CRT/LBBP vs ICD concurrently. 
 
3.3.3 Definition of Study Endpoints 
1. Definition of new-onset AF after device implantation: AF episodes 
with a duration of at least 30 seconds detected by pacemaker 
programming or surface 12-lead ECG, confirmed as AF by manually 
checking atrial high-rate episodes (atrial rate ≥190 bpm) detected by 
the device. 
2. All-cause death: Refers to death from any cause occurring during 
the study period, including cardiovascular death and non-
cardiovascular death. 
3. HF rehospitalization event: Refers to rehospitalization treatment 
events caused by exacerbation of HF during the study period. 
Patients are required to have: A. New or worsened HF symptoms; B. 
Objective evidence of HF exacerbation, including physical 
examination or laboratory indicators; C. Dose escalation of original 
HF treatment drugs, application of intravenous therapeutic drugs or 

initiation of mechanical or surgical intervention therapy. 
3.3.4 Definition of Successful Bachmann Bundle Pacing 
1. Judgment of Bachmann bundle pacing by paced ECG manifestations: 
Positive P waves in leads I, II, III and aVF, similar to normal sinus 
rhythm; biphasic or negative P waves in lead V1; peaked and 
symmetrical P waves in inferior leads, with the amplitude of paced 
P waves generally greater than that of sinus P waves; compared with 
sinus P wave duration, the P wave duration of Bachmann bundle 
pacing is narrowed, and if underlying intraatrial block exists, the 
narrowing is usually more than 10 ms. 
2. Judgment of Bachmann bundle pacing by combining intraoperative 
intracavitary ECG and paced surface ECG manifestations: 
Recording of Bachmann bundle potentials; narrowed P wave 
duration of Bachmann bundle pacing compared with sinus P wave 
duration; similar P wave morphology and electrical axis of 
Bachmann bundle pacing to sinus P waves; transformation of P wave 
morphology of Bachmann bundle pacing from non-selective to 
selective under high and low pacing output voltages. 
3.3.5 Measurement Method of Paced QRS Complex Duration 
Measurement is performed at a paper speed of 100 mm/s and an output of 
2 V/0.4 ms on a multichannel recorder. The QRS complex duration is 
defined as the time from the pacing signal to the end of the QRS complex 

in lead V1. 
3.3.6 CIED Adverse Events 
Including perioperative death, surgery-related cardiac tamponade, 
pericardial effusion, pneumothorax, hemothorax, lead displacement, 
ventricular septal perforation, implant system infection, etc. 
3.4 Early Termination of the Study 
Triggers for early termination: Combining the study design objectives 
and risk control priorities, the core scenarios triggering early termination 
include the following two categories: 
1. Efficacy-related termination criteria: 
1.1 Clear superiority or ineffectiveness shown by interim data analysis: The 
independent statistical team conducts interim data monitoring according to 
the preset protocol (e.g., when 50% of patients are enrolled or at 6 months 
of follow-up). Termination assessment can be initiated if the following 
conditions occur: 
a) Excessive superiority: The incidence of new-onset AF within 12 months 
in the Bachmann bundle pacing group is significantly lower than that in the 
traditional group (e.g., intergroup difference ≥30% and P<0.001), and the 
trend is still maintained after continuous verification. From an ethical 
perspective, continuing to let the control group receive traditional pacing 
may deprive patients of benefits, and early termination is required to 
promote the optimal scheme. 

b) Confirmation of ineffectiveness: Interim data show no statistically 
significant difference in the incidence of new-onset AF between the two 
groups (P>0.5), and subgroup analysis (CRT/LBBP subgroup, ICD 
subgroup) does not suggest the advantage of Bachmann bundle pacing. 
Continuing enrollment will fail to achieve the study objectives and cause 
resource waste. 
1.2 Emergence of alternative therapies or new evidence: If high-level 
evidence-based evidence (e.g., multicenter RCT) is published during the 
study, confirming the ineffectiveness of Bachmann bundle pacing in the 
same population or the existence of a better alternative technology, the 
study needs to be terminated from the perspective of scientific rationality. 
2. Safety-related termination criteria: 
2.1 Clustered occurrence of serious adverse events (SAEs): If SAEs 
directly related to the intervention occur in the Bachmann bundle pacing 
group, the study must be suspended immediately and termination assessed 
if any of the following conditions is met: 
a) Two or more SAEs of the same type occur in a single center (e.g., 
intraoperative cardiac tamponade, severe arrhythmia caused by lead 
displacement within 30 days after surgery), and are judged by adverse 
event assessment experts to be directly related to Bachmann bundle pacing 
operation. 
b) The incidence of SAEs in the group is significantly higher than the preset 

safety threshold (e.g., perioperative SAE incidence >10%, far exceeding 
the baseline reference of "traditional pacing complication incidence of 
about 3%-5%" in the application), or significantly higher than that in the 
control group (e.g., the incidence of SAEs in the Bachmann bundle group 
is 3 times or more that in the traditional group). 
2.2 Failure of safety verification of pacing technology: Unexpected long-
term safety risks of Bachmann bundle pacing are found during post-
operative follow-up, such as: 
a) Unstable pacing parameters: Pacing threshold continues to increase 
(more than 50% higher than the intraoperative baseline value) within 3 
months after surgery and cannot be improved by programming, resulting 
in a pacing failure rate >15%. 
b) Delayed complications: Occurrence of delayed pericardial effusion, 
cardiac structural injury (e.g., atrial septal perforation) related to electrode 
implantation, with an incidence exceeding the clinically acceptable range. 
4 Sample Size Estimation and Statistical Analysis 
4.1 Sample Size Estimation 
This study is a prospective, single-blinded, randomized controlled study, 
with the experimental group receiving Bachmann bundle pacing and the 
control group receiving traditional atrial pacing. Since there are no relevant 
research reports on the effect of Bachmann bundle pacing on new-onset 
AF in patients with cardiac insufficiency at present, based on previous 

research results and clinical experience, the incidences of paroxysmal AF 
progressing to persistent AF after traditional atrial pacing and Bachmann 
bundle pacing are 53% and 25%, respectively. The sample size is 
calculated with reference to the above trial results. With a two-sided test 
significance level of α=0.05 and a power of 0.9, the sample size ratio of 
the experimental group to the control group is set to 1:1, and considering a 
certain loss to follow-up rate (not exceeding 10%), the final planned 
enrollment number of this study is 140 cases, including 70 cases in the 
experimental group and 70 cases in the control group. 
The specific reference is as follows: BAILIN S J, ADLER S, GIUDICI M. 
Prevention of chronic atrial fibrillation by pacing in the region of 
Bachmann's bundle: results of a multicenter randomized trial [J]. J 
Cardiovasc Electrophysiol, 2001, 12(8): 912-7. 
4.2 Statistical Analysis Plan 
The trial data of this study will be analyzed in accordance with the ITT 
principle. The specific analysis methods include: descriptive analysis using 
mean ± standard deviation or frequency and percentage according to 
variable types; comparison of baseline balance between groups using 
independent samples t-test, Wilcoxon rank-sum test (for quantitative 
indicators with normal or non-normal distribution), or chi-square test and 
Fisher's exact probability test (for qualitative indicators); for the primary 
endpoint indicator, analysis of covariance is used to compare the 

differences in new-onset AF or atrial high-rate events between patients 
with different pacing modes, with block factors as covariates. Similar 
statistical analysis methods to baseline are used for secondary and safety 
indicators; further subgroup analysis is performed when necessary to 
evaluate the reliability of the trial results. Statistical software such as SPSS 
(IBM, USA), Stata (StataCorp, USA) or R language is used for statistical 
analysis. 
Combined with the study design type of "multicenter, prospective, single-
blinded, randomized controlled" and the core objective of "evaluating the 
preventive effect of Bachmann bundle pacing on new-onset AF in HF 
patients", a two-sided test is uniformly adopted with a strict test level of 
α=0.05. The specific application scenarios and basis are as follows: 
Primary endpoint analysis (core efficacy judgment) 
For the primary endpoint of this study: "whether new-onset AF occurs 
during the follow-up after device implantation". Calculate the incidence of 
new-onset AF in the experimental group and the control group at 12 
months after surgery, estimate the difference in the incidence of new-onset 
AF at 12 months after surgery between the two groups and its 95% 
confidence interval (CI), and compare the lower limit of the CI of the 
difference with 0 to judge whether the superiority hypothesis is established. 
Meanwhile, the Kaplan-Meier (KM) method is used to estimate the 
difference in the incidence of new-onset AF at 12 months after surgery and 

its 95% CI as a sensitivity analysis. 
Secondary endpoint analysis (supportive efficacy and safety judgment) 
For secondary endpoints (e.g., time to first new-onset AF after device 
implantation, surgical success rate, changes in cardiac function indicators, 
incidence of complications, etc.), the test level is set to α=0.05 
synchronously without multiple test correction. The specific logic is as 
follows: 
1. Time to first new-onset AF: The "AF-free survival curve" of the two 
groups is plotted by the Kaplan-Meier method, and the log-rank test 
is used to compare the differences between the curves, also with 
α=0.05 as the boundary. If P<0.05, it indicates that Bachmann 
bundle pacing has an advantage in delaying the occurrence time of 
new-onset AF, which is consistent with the core study objective of 
"reducing the risk of AF occurrence and improving prognosis". 
2. Surgery-related indicators: When comparing the immediate surgical 
success rate and the incidence of perioperative complications (e.g., 
lead displacement, pericardial effusion) between the two groups, the 
chi-square test or Fisher's exact probability test is used. α=0.05 is 
used to judge the technical feasibility and safety of Bachmann 
bundle pacing. If P<0.05, it indicates that this technology is superior 
to traditional pacing in surgical effect or safety. 
3. Cardiac function and electrophysiological indicators: When 

analyzing echocardiographic parameters (LVEDD, LVESV, atrial 
size, etc.), NYHA classification improvement rate, changes in 6-
minute walk distance, reduction amplitude of NT-proBNP level, and 
differences in ECG P-wave duration/amplitude between the two 
groups, the independent samples t-test (for normally distributed data) 
or Wilcoxon rank-sum test (for non-normally distributed data) is 
used. α=0.05 is used to verify whether Bachmann bundle pacing can 
simultaneously 
improve 
cardiac 
function 
and 
atrial 
electrophysiological stability. 
Subgroup analysis (exploratory conclusions) 
When conducting subgroup analysis stratified by "type of implanted 
device" (CRT/LBBP subgroup, ICD subgroup), the comparison of 
"whether new-onset AF occurs" within each subgroup still adopts α=0.05, 
but it is clearly stated that this analysis is an exploratory conclusion and 
not used as the sole basis for the final efficacy judgment: 
1. Only when P<0.05 is shown in each subgroup (CRT/LBBP subgroup, 
ICD subgroup) and the effect direction is consistent (all indicating 
the superiority of Bachmann bundle pacing), it can assist in 
explaining the consistency of the efficacy of this technology in 
populations treated with different devices; 
2. If heterogeneity occurs between subgroups (e.g., P<0.05 in one 
subgroup and P>0.05 in another), further analysis should be 

conducted in combination with patients' baseline characteristics to 
avoid overinterpreting the exploratory results and affecting the core 
conclusions, which is consistent with the study design logic of 
"focusing on the primary endpoint and taking into account the 
secondary endpoints". 
5 Data Management 
This study is a multicenter randomized clinical study. The Uncom Medical 
Research Cloud Platform EDC system is used for data entry and 
verification. The principal investigator, Director Fan Xiaohan, has full 
access and management rights to all data. Data entry personnel only have 
the right to enter data, without the rights to delete, export or store data. If 
an application for data modification is required, a modification application 
must be submitted to Director Fan Xiaohan, and the modification can only 
be made after approval. All entered data is encrypted and de-identified on 
the platform, and the data entry quality controller is responsible for manual 
verification. For the future use of data, a data analysis plan must be 
provided and submitted to Chief Physician Fan Xiaohan, and the 
application for use can only be made after discussing the feasibility. All 
applications are traceable on the platform. 
6 Confidentiality Principles 
Issue of protecting subjects' right to informed consent and 
autonomous choice: Inadequate informed of study details may lead to 

incomplete informed consent of subjects and affect autonomous decision-
making. 
Countermeasures: Strictly follow the Declaration of Helsinki. Before the 
start of the study, researchers shall comprehensively and clearly introduce 
the study purpose, process, potential risks and benefits to subjects or their 
legal representatives in writing, and give sufficient time for consideration; 
subjects can be enrolled only after signing the informed consent form 
approved by the ethics committee; if new safety information appears 
during the study, the informed content must be updated and re-signed, and 
it is clearly stated that subjects have the right to withdraw from the study 
at any time without reason, and this will not affect subsequent conventional 
treatment. 
Issue of balancing study protocol compliance and subject safety: 
Bachmann bundle pacing is a relatively new physiological pacing 
technology with a certain risk of operation failure, and the study population 
is patients with chronic cardiac insufficiency with low physical tolerance, 
so it is necessary to balance technological exploration and patient safety. 
Countermeasures: The study protocol is implemented only after being 
approved by the ethics committee to ensure no off-label treatment; an 
intraoperative emergency plan is formulated for the failure of Bachmann 
bundle pacing, and if it fails, the clinically mature traditional atrial pacing 
is immediately performed to ensure effective treatment for the patient; a 

special follow-up management group is established to regularly evaluate 
the patient's condition and risks, record adverse events (e.g., exacerbation 
of HF, surgical complications, etc.), and take intervention measures in a 
timely manner to minimize safety risks. 
Issue of protecting subjects' privacy and data security: The study 
involves sensitive information such as patients' personal health records, 
cardiac imaging data and follow-up data, with the risk of privacy leakage. 
Countermeasures: Establish a strict data management system; all collected 
data are desensitized to remove personally identifiable information; the 
leading center and participating centers clarify the rights to data storage 
and use; original data are properly preserved by each study center, and 
desensitized data are only used for study analysis; regularly verify the data 
management process to ensure compliance with relevant privacy 
protection regulations and prevent data leakage. 
Issue of ensuring study quality and result credibility: Non-standard data 
collection and inconsistent evaluation standards may affect the authenticity 
of study results, indirectly damage the scientificity of medical decision-
making, and thus affect the rights and interests of future patients. 
Countermeasures: Before the study, conduct training for all participating 
researchers to unify data collection standards, endpoint definitions and 
operation specifications; establish a core echocardiographic laboratory 
composed of three senior ultrasound experts, and adopt blinded image 

review to analyze cardiac ultrasound data at baseline and follow-up to 
reduce assessment bias; conduct pre-collection and pre-analysis of data 
from a small number of preliminary cases to correct data collection 
problems in a timely manner; the leading center verifies the data of each 
center every month, requires the provision of original data for verification 
of questionable data, and eliminates unqualified data to ensure study 
quality. 
7 Quality Control of the Study 
Quality control: The following measures will be adopted for quality 
control in this study: 1) Before the official start of the study, researchers 
from participating centers will be organized to receive training on the study, 
including the study protocol, specific definitions, data collection standards, 
etc. All study centers must collect data in strict accordance with the trial 
protocol, and the collected variables shall be accurately defined in 
accordance with the study protocol to ensure data quality. 2) Establish a 
core echocardiographic laboratory (composed of three senior ultrasound 
experts). Cardiac ultrasound data at baseline and follow-up are analyzed 
by the core echocardiographic laboratory through blinded image review to 
extract data. 3) Each center conducts preliminary pre-collection of data 
from a small number of cases in the early stage, and the data are collected 
by the leading center for pre-analysis, so as to find and correct problems in 
the data collection process in a timely manner and conduct re-training. The 

official data collection can only be started after the quality of the pre-
collected data is confirmed to be qualified. 4) The leading center will be 
equipped with professional and technical personnel to collect data every 
month at the beginning of the study and conduct regular verification of the 
data collected by each study center to uniformly control the data quality. 
For questionable data after verification, each study center shall provide 
original data and objective evidence for confirmation, and the data still 
questionable after verification shall be eliminated. The person in charge of 
the data source center shall bear the impact caused by incorrect data 
collection. 
8 Organizational Management of the Study 
In this study, the principal investigator, Chief Physician Fan Xiaohan, is 
responsible for determining the study plan, screening patients, implanting 
devices, interpreting results and writing papers. Well-trained doctors and 
engineers will conduct device testing during follow-up and data entry. Data 
verification and quality control are managed and performed by a 
professional team from Fuwai Hospital, Chinese Academy of Medical 
Sciences to ensure the smooth progress of the study and the authenticity 
and completeness of the data. 
9 Ethical Principles 
This study strictly follows the Declaration of Helsinki and relevant clinical 
research ethical norms to protect the legitimate rights and interests and 

safety of study participants. The specific requirements are as follows: 
9.1 Ethical Committee Approval 
Before enrolling study participants, ethical committee approval for the 
study protocol and informed consent form must be obtained. During the 
study, annual ethical review reports must be submitted on time to ensure 
that the study progress complies with ethical requirements. If the study 
protocol is revised, an ethical amendment review must be submitted in a 
timely manner, and the revised protocol can only be implemented after 
approval. 
9.2 Informed Consent of Study Participants 
Before study participants participate in this clinical study, researchers shall 
use the Ethics Committee-approved version of the Informed Consent Form 
for Study Participants (ICF) to fully inform participants or their legal 
representatives of all relevant information about participating in the study, 
including the study purpose, process, potential risks and benefits, data 
usage methods, etc. Written informed consent from participants or their 
legal representatives must be obtained. During the process, any coercion, 
inappropriate influence or inducement shall be avoided, and the legitimate 
rights of study participants shall not be infringed or waived in a disguised 
form. If a study participant is unable to read or write, a fair third party is 
allowed to act as a witness to assist in completing the ICF signing and data 
protection-related processes. The witness must sign and indicate the date 

on the ICF and relevant authorization documents. The signed ICF shall be 
filed at the study center for supervision and review, and a signed and dated 
copy of the ICF must be provided to the study participant. During the entire 
study process, if important new information related to the study appears, it 
must be informed in writing to newly enrolled and already enrolled 
subjects; if the relevant information affects the subjects' willingness to 
continue participating in the study, all affected subjects are required to 
confirm their continued informed consent in writing. 
9.3 Withdrawal of Subjects 
Subjects have the right to voluntarily withdraw from the study at any time 
during the study process without giving reasons, and the withdrawal will 
not affect their subsequent conventional treatment rights and interests. 
After a subject withdraws from the study, no further study data will be 
collected from them, and no further study-related visits will be conducted. 
However, all available data collected before withdrawal will be used for 
statistical analysis in accordance with the study protocol, and data 
processing will strictly follow the confidentiality principles. If a subject 
chooses to withdraw, the researcher must record the reason for withdrawal 
in detail and file it in the study archives. After the completion of implant-
related device implantation, if a subject withdraws, no new subjects will 
be enrolled to replace them. 
10 References 

(1) Fan X, Yao Y. Current status of atrial fibrillation after pacemaker 
implantation [J]. Chinese Circulation Journal, 2014, 29(10): 852-4. 
(2) BAILIN S J, ADLER S, GIUDICI M. Prevention of chronic atrial 
fibrillation by pacing in the region of Bachmann's bundle: results of a 
multicenter randomized trial [J]. J Cardiovasc Electrophysiol, 2001, 12(8): 
912-7. 
(3) INFELD M, NICOLI C D, MEAGHER S, et al. Clinical impact of 
Bachmann’s bundle pacing defined by electrocardiographic criteria on 
atrial arrhythmia outcomes [J]. EP Europace, 2022, 24(9): 1460-8. 
(4) LUSTGARTEN D L, HABEL N, SÁNCHEZ-QUINTANA D, et al. 
Bachmann bundle pacing [J]. Heart Rhythm, 2024, 21(9): 1711-7. 
(5) GLIKSON M, NIELSEN J C, KRONBORG M B, et al. 2021 ESC 
Guidelines on cardiac pacing and cardiac resynchronization therapy [J]. 
Eur Heart J, 2021, 42(35): 3427-520. 
(6) ZHU H, LI X, WANG Z, et al. New-onset atrial fibrillation following 
left bundle branch area pacing vs. right ventricular pacing: a two-centre 
prospective cohort study [J]. Europace, 2023, 25(1): 121-9. 
(7) SUBRAMANIAN M, YALAGUDRI S, SAGGU D, et al. Electrogram-
guided Bachmann bundle area pacing to correct interatrial block: Initial 
experience, safety, and feasibility [J]. Heart Rhythm, 2025, 22(4): 1064-70. 
(8) WANG Y, ZHU H, HOU X, et al. Randomized Trial of Left Bundle 
Branch vs Biventricular Pacing for Cardiac Resynchronization Therapy [J]. 

J Am Coll Cardiol, 2022, 80(13): 1205-16. 
 
11 Participating Study Centers and Principal Investigators 
Leading Study Center: 
Fuwai Hospital, Chinese Academy of Medical Sciences 
Principal Investigator: Fan Xiaohan 
Participating Study Centers: 
Zhongshan Hospital, Fudan University 
Principal Investigator: Chen Xueying 
Fuwai Huazhong Cardiovascular Hospital 
Principal Investigator: Chen Ke 
Tianjin Chest Hospital 
Principal Investigator: Xu Jing