Change of QRS Morphology and Electrophysiological Characteristics During Pacing Within the Interventricular Septum

Study Overview
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Brief Summary
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Conduction system pacing (CSP), including His bundle pacing (HBP) and left bundle branch (LBB) pacing (LBBP), as a physiological pacing strategy, can achieve interventricular and/or intra-left ventricular mechanical synchronization by delivering physiological or nearly physiological ventricular activation. And many studies have verifed clinical efficacy of CSP that it can significantly relieve dyssynchrony of ventricular contraction, improve cardiac function and reduce the risk of heart failure as compared to right ventricular pacing. However, CSP has some shortcomings which limit its widespread application to some extent. As for HBP, although it can achieve optimal physiological ventricular synchronization, the problems of relatively high pacing threshold, low R-wave amplitude, the long-term performance, and inability to correct infra-Hisian atrioventricular block and intraventricular block in some patients have always been concerns. Nevertheless, LBBP is likely free of the restrictions mentioned above. On the contrary, LBBP can capture the left conduction system by directly stimulating the proximal LBB distal to the site of conduction block, thereby achieving rapid and physiological LV activation with a lower and stable pacing threshold and higher R-wave amplitude. However, as a newly emerged physiologic pacing technology, LBBP is currently in the exploratory stage and there are some phenomena to be interpreted, such as the evolution of pacing QRS morphology during the lead penetration into the interventricular septum. Therefore, the aim of this study is to assess the morphological evolution and electrophysiological characteristics of various pacing QRS patterns observed as the lead penetrates the interventricular septum from right to left.

Official Title
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Change of QRS Morphology and Electrophysiological Characteristics During Pacing Within the Interventricular Septum: a Prospective, Observational Study

Conditions
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Cardiac Pacing

Intervention / Treatment
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* Procedure: left bundle branch pacing


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: The indications for pacemaker implantation are in accordance with the 2021 European Society of Cardiology (ESC) guidelines. Patients requiring a high percentage of ventricular pacing (>40% expected ventricular pacing) include patients with advanced or third-degree atrioventricular block and atrial fibrillation with bradycardia. Left bundle branch pacing will be performed. Patients voluntarily participate and sign informed consent. Exclusion Criteria: Atrioventricular block caused by reversible factors such as acute myocardial infarction and electrolyte disturbance. Patients with severe liver or renal failure. Life expectancy < 1 year. Patients with age < 18 years. Left ventricular ejection fraction (LVEF) < 40%.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| All patients<br>Patients who meet the inclusion criteria | Procedure: left bundle branch pacing<br>* In the procedure of left bundle branch pacing, various QRS morphologies are observed as penetrating the lead into the interventricular septum.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Left ventricular activation time (LVAT) | Left ventricular activation time (LVAT) is defined as the interval from the onset of the pacing stimulus to the peak of the R wave in lead V5/6, which reflects the lateral precordial myocardium depolarization time. | Continuous uninterrupted monitoring during the lead penetration into the interventricular septum. | 
| Right ventricular activation time (RVAT) | Right ventricular activation time (RVAT) is defined as the interval from the onset of the pacing stimulus to the peak potential recorded by the atrial electrode temporarily placed in the right ventricle, which reflects delayed right ventricular activation. | Continuous uninterrupted monitoring during the lead penetration into the interventricular septum. | 
| Paced QRS morphology | Paced QRS morphology during lead penetration through the interventricular septum mainly includes left bundle branch block, intraventricular block and right bundle branch block. | Continuous uninterrupted monitoring during the lead penetration into the interventricular septum. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Stimulus-QRSend duration (s-QRSend) | Stimulus-QRSend duration (s-QRSend) is the time from the onset of the pacing stimulus to the end of QRS complex. | Continuous uninterrupted monitoring during the lead penetration into the interventricular septum. | 
| The late-R wave duration and amplitude in lead V1 (r´dur、r´amp) | The late-R wave duration in lead V1 indicates delayed right ventricular excitation. | Continuous uninterrupted monitoring during the lead penetration into the interventricular septum. | 
| The S wave duration and amplitude in lead V6 (Sdur、Samp) | The S wave duration in lead V6 indicates delayed right ventricular excitation. | Continuous uninterrupted monitoring during the lead penetration into the interventricular septum. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Left Bundle Branch Pacing, Left Bundle Branch Area Pacing, Septal Pacing, Left Ventricular Activation Time, Right Ventricular Activation Time