Low prevalence of CRT upgrade in patients with significant RV pacing: 10-year real-world data in a UK DGH

In heart failure patients with reduced ejection fraction (HFrEF) requiring a pacemaker, biventricular cardiac resynchronisation therapy (CRT) is preferred to right ventricular (RV) pacing. Moreover, HFrEF patients who already have a conventional pacemaker in situ should be considered for CRT ‘upgrade’ in the presence of worsening symptoms and a significant proportion of RV pacing. While international guidelines are clearly defined, the ‘real-world’ prevalence of upgrading to CRT in patients with a significant proportion of RV pacing remains unclear. We aim to report the prevalence and characteristics of CRT upgrades in a UK district general hospital over a 10-year period.

We performed a retrospective univariate analysis of consecutive adult patients who underwent pacemaker implantation for Mobitz type 2 and complete atrioventricular (AV) block from January 2009 to December 2018. Over the study period, 34 patients were upgraded to CRT (prevalence 4.6%). Male patients were more likely to receive CRT upgrade (p=0.027). There was no statistically significant difference in RV-pacing burden or RV-paced QRS duration between CRT upgrade and non-upgrade groups. Patients who received CRT had lower baseline left ventricular (LV) ejection fraction than the non-upgrade group (50% vs. 60%, p=0.049).

In conclusion, this real-world study supports the notion that patients with impaired LV function and likely high requirements for RV pacing should be informed of the possible future need for device CRT upgrade. CRT should be considered upfront in selected patients with lower baseline LV systolic function.

Introduction

Chronic right ventricular (RV) pacing is associated with deterioration in cardiac function, increased mortality and heart failure hospitalisation.¹ The UK PACE (United Kingdom Pacing and Cardiovascular Events) trial reported an overall annual incidence of clinical heart failure (HF) of approximately 3% in patients implanted with either a single-chamber or dual-chamber pacemaker over a three-year follow-up duration.² A broader-paced QRS duration at baseline and the presence of coronary artery disease (CAD) are independently associated with new-onset HF in patients requiring permanent RV pacing for high-degree atrioventricular (AV) block and normal left ventricular (LV) function.³ Paced QRS duration and RV pacing percentage (>20%) are associated with the incidence of pacing-induced cardiomyopathy (PICM) in patients with complete AV block.^3–5 In patients requiring a permanent pacemaker for AV block with New York Heart Association (NYHA) class I–III symptoms and a LV ejection fraction (LVEF) less than 50%, cardiac resynchronisation therapy (CRT) with biventricular pacing appears to be superior to RV pacing in reducing mortality, morbidity and adverse LV remodelling.⁶ Despite the publication of international recommendations for CRT implantation, a European Society of Cardiology (ESC) survey conducted in 2008–2009 demonstrated considerable variation in guideline adherence and significant individual, national and regional differences in patient selection, implantation practice and follow-up.⁷ This study aims to report the prevalence and characteristics of patients undergoing CRT upgrade of pacemakers implanted for higher degree AV block in a UK district general hospital (DGH) over a 10-year period.

Method

Study population

We performed a retrospective single-centre study of consecutive adults aged over 18 years who received a permanent pacemaker (PPM) implant for complete AV block and/or Mobitz type 2 AV block in a UK DGH between January 2009 and December 2018. We identified pacemaker implants from the hospital cardiology database. A total of 739 patients were included for analysis. Patients with pacemaker implants for Mobitz type 1 AV block, symptomatic marked first-degree AV block, sinus bradycardia, generator change, lead replacement and device revision were excluded.

Clinical data and measurements

We collected data regarding patient demographics, comorbidities and medication from the local electronic and patient medical notes. Post-pacemaker device data were collected from the local device database. Paced QRS duration was recorded from electrocardiograms (ECGs) stored in the electronic patient record. Echocardiographic data pre-pacemaker and pre-CRT upgrade were recorded from hospital reports. Missing assessments of LV function were reviewed blindly by the authorship team.

Statistical analysis/methods

Parametric variables are given as mean and standard deviation (SD). Non-parametric variables are given as a median and interquartile range (IQR). We performed univariate analysis by comparing the mean and median values using the Mann-Whitney test and proportions of baseline variables using Pearson’s Chi-square test. Univariate analysis was performed on categorical data using the Fisher Chi-square exact test.

Results

A total of 739 patients, median age 88 (80–94), 62% male, were suitable for analysis. The baseline characteristics of the patients are summarised in table 1. In total, 632 patients (86%) received dual-chamber and 107 (14%) single-chamber pacemaker implantation. Out of 580 patients, 408 (70%) had an RV-pacing burden of >40% (table 2). Over a median follow-up period of 84 (range 52–116) months, 34 patients were upgraded to CRT (prevalence 4.6%). There was no statistically significant difference between CRT upgrade and non-upgrade groups in baseline pacing indication, RV-pacing burden or RV-paced QRS duration. Patients who received CRT had lower baseline LVEF than the non-upgrade group (50% vs. 60%, p=0.049). Male patients were more likely to receive CRT upgrade (p=0.027). Beta-blocker administration was greater in the upgrade group compared with the non-upgrade group: 24 (80%) vs. 155 (32%), p<0.001. Almost 60% (19 out of 33) of CRT upgrade patients underwent the procedure within three years from the initial PPM implant.

Discussion

Our study demonstrates that 4.6% of patients requiring a PPM for high-degree AV block required CRT upgrade within a mean duration of three years from initial pacemaker implant. Male patients, reduced LV systolic function at baseline and beta-blocker use were associated with requiring early CRT upgrade. We found no association with paced QRS duration or RV-pacing requirement.

Overall, rates of CRT upgrade over a 10-year study duration were not high in this real-world elderly population, however, it occurred in one in 20 patients within three years. The average LVEF in the upgrade group was severely reduced, by 34%. Despite a high requirement for pacing, 69% in non-upgrade and 81% in the upgrade group of patients with over 40% RV pacing, we found no statistical association with either RV-pacing requirement or paced QRS duration. The usage of beta blockers was statistically significantly more prevalent in the upgrade group. This is likely to be reflective of good clinical practice in treating HF patients with this therapy, rather than causative of HF.

The BLOCK HF (Biventricular versus Right Ventricular Pacing in Heart Failure Patients with Atrioventricular Block) trial demonstrated the superiority of CRT over RV pacing, for patients with similar characteristics as our upgrade group, in terms of the composite end point of death, heart failure hospitalisation and adverse ventricular remodelling, but also for clinical outcomes, such as NYHA class and quality of life. These findings suggest that biventricular pacing may improve current symptoms due to existing ventricular dyssynchrony and prevent future dyssynchrony and heart failure.^6,8

Recent research has increasingly highlighted the potential benefits of left bundle branch pacing (LBBP). The LBBAP-CRT (LEFT Bundle Branch Area Pacing for Cardiac Resynchronization Therapy) trial, explored the effectiveness of LBBP compared with conventional biventricular pacing in patients with LVEF below 50% who required CRT or pacing. The results of this trial suggest that LBBP may serve as a promising alternative, especially for patients who do not respond well to traditional CRT approaches.⁹

LBBP is often seen as more technically straightforward than His-bundle pacing (HBP). This is due to its larger target area and the deeper implantation within the right ventricle, which is positioned further from the atrial myocardium. These factors contribute to a shorter learning curve, making LBBP more accessible and easier to master for practitioners.¹⁰

This real-world study supports the notion that patients should be informed of the possible future need for device CRT upgrade. CRT should be considered upfront in selected patients with impaired LV function and likely high requirements for RV pacing. Closer echocardiographic monitoring could be considered in patients with borderline systolic function at baseline.

Limitations

The results of our study were limited to a retrospective analysis and a long study period, including paper and electronic records. Assessment of LV systolic function pre- and post-PPM implantation and paced QRS duration were guided clinically and not systematically performed. The lack of detailed data on device upgrade attempts that were unsuccessful or required lead extraction prior to upgrading may result in overlooking the challenges and risks associated with upgrading previously implanted devices.

Key messages

• The rate of cardiac resynchronisation therapy (CRT) upgrades among patients with advanced atrioventricular (AV) block and permanent pacemaker (PPM) implantation was lower than anticipated
• No significant association was found between CRT upgrade and factors such as pacing percentage or paced QRS complex duration in this cohort
• Patients with lower baseline left ventricular (LV) systolic function were more likely to experience further LV function deterioration after PPM implantation, subsequently necessitating device upgrade

Conflicts of interest

None declared.

Funding

None.

Study approval

As the study was deemed to be a clinical audit, approval from local ethic committee was not required. All patients received information sheets during their first clinical encounter explaining that their anonymised data may be used for clinical audit and service evaluation.

Acknowledgements

The authors would like to thank Justine Vinuya, Michael Phillips, Dr Alex Liu, Dr Sein L Aung, Dr Beenish Aujum, Dr Priyanga Belandran, Dr Junaid Anvar, Dr Jill Betts and Dr Nish Mehta who helped in data collection.

References

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