Role of RA-LV pacing in patients with symptomatic left bundle branch block with CRT - a single centre experience
Authors: Jhala M , Chennapragada S , Subramanium M , Sutar B , Krishnamurthy P , Saggu D , Yalagudri S , Gollapally D , Narasimhan C 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: None.

Introduction
Cardiac Resynchronisation Therapy(CRT) is considered as the cornerstone of treatment for patients with heart failure and left ventricular conduction delay ( left bundle branch block) who remain symptomatic despite optimal medical therapy. However, it has been well documented that the responder and success rates of this therapy are highly variable. Contemporary response rates from clinical trials as well as real world data demonstrate non-response rates of between 30–50%. Suboptimal AV delay timing is the most prevalent modifiable factor on follow up for improving response rates. AV Fusion pacing describes the delivery of CRT pacing with a programming strategy to preserve intrinsic atrioventricular (AV) conduction and ventricular activation via the right bundle branch. This concept is utilised in the RA- LV pacing strategies, which have been described in literature. However, RA-LV only pacing raises certain practical , moral and ethical concerns as it has never been a part of contemporary guidelines nor a part of large randomised control trial.

Purpose
The purpose of this study was to study the clinical as well as hemodynamic effects of RA-LV pacing in patients with a conventional CRT device with a programmed subthreshold RV lead.

Methods
All patients with a convention CRT indication ( CRT-P as well as CRT-D), with acceptable intrinsic AV conduction, non pacing dependent and normal Right Ventricular function were enrolled into the study. A total of 60 consecutive patients between 2016-2021 were enlisted from after the implant and followed up in the Device clinic of the institution. The baseline as well as follow-up LV function, Battery life and QRS duration was recorded and analysed.

Results
Total of 60 patients were enlisted of which 30 were males and 30 females. There were 16 patients were with Ischemic Cardiomyopathy in this group. The average follow-up period was 3 year from implant. The mean baseline Left Ventricular Ejection Fraction was 29% while the mean follow-up Left Ventricular Ejection Fraction was 46.5%. The mean QRS duration at implant was 155msec and the mean follow-up QRS was 123 msec. The subset analysis of ischemic vs the nonischaemic cardiomyopathy groups revealed that both groups had a similar response rates to improvement of clinical as well as Echocardiographic parameters including LVEF. The mean follow up LVEF in the ischemic and nonischaemic groups were 44.5 & 46.5% respectively. This finding suggests that the advantage of AV fusion pacing is not significantly impacted with underlying aetiology of the Cardiomyopathy.

Conclusion
RA-LV with RV subthreshold CRT is a reasonable strategy for achieving traditional response rates of CRT in patients with a good intrinsic AV conduction. This modality overcomes a large number of procedural as well as ethical roadblocks in the use of fusion pacing for CRT therapy optimisation.