From pacing to resynchronization: determinants of CRT upgrade success in a regional hospital setting

Introduction

Right ventricular (RV) pacing can lead to intraventricular desynchrony, resulting in left ventricular (LV) dysfunction and worsening heart failure (HF) in approximately 30% of patients within a few years of device implantation. Cardiac resynchronization therapy (CRT) has been shown to reverse these adverse effects, improving LV ejection fraction (LVEF) and reducing morbidity and mortality. Despite these benefits, 20–40% of CRT recipients do not demonstrate a significant response. Previous studies have suggested that specific patient characteristics may predict a higher likelihood of benefiting from CRT.

Purpose

To identify variables associated with CRT response within a year of CRT upgrade in a district hospital.

Methods

We conducted a single-center, retrospective, observational study including patients with RV pacing devices and HF with reduced LVEF who underwent upgrade to CRT between January 2015 and December 2024. CRT response was defined as an improvement in ≥1 category in New York Heart Association (NYHA) functional class and ≥5% in LVEF, which was measured prior and 6-12 months post-upgrade.

Results

A total of 55 patients were included (78% male), with a mean age of 76±7.9 years. 64% had a double chamber PM and 20% an ICD. The mean RV pacing percentage was 78±33%, and the average time from initial device implantation to CRT upgrade was 8±2.6 years. The mean age at upgrade was 73±7 years. All CRT procedures were successful (CRT-D 76%, CRT-P 24%). HF etiology was ischemic in 54% of patients and 49% had atrial fibrillation. All patients were in NYHA II–III, with a baseline mean LVEF of 29.1±6.7%.

CRT response was observed in 64% of patients (n=35), with a mean ΔLVEF of 10.7±8.9%. All responders also showed NYHA class improvement: 49% (n=27) were NYHA I and 44% (n=24) were NYHA II at follow-up. Patients with non-ischemic cardiomyopathy exhibited a significantly higher response rate compared to ischemic patients (ΔLVEF: 14±9.9 vs. 7.9±5.8, p=0.019). Age <70 years at the time of upgrade was also associated with greater LVEF improvement (ΔLVEF: 12.5±9.8 vs. 10±7.1, p=0.002). Additionally, patients with RV pacing ≥40% showed higher rates of response (ΔLVEF: 11.9±6.6 vs. 10±4.4, p=0.022). Gender, sinus rhythm, time between initial implant and revision, and device type were not significant predictors of CRT response during the 6–12 month follow-up.

Conclusion

Upgrading to CRT in patients with HF and reduced LVEF resulted in a high response rate, with the most pronounced benefits seen in those with non-ischemic HF, age <70 years at the time of upgrade, and higher baseline RV pacing. These results, coming from a district hospital context, emphasize the real-world efficacy of CRT and reinforce the value of implementing CRT programs in regional healthcare settings.