Clinical characteristics of patients with better ejection fraction recovery after upgrading to cardiac resynchronization therapy
Authors: Vujadinovic N , Radovanovic N N , Kircanski B , Milasinovic A , Brankovic N , Sajic V , Zivkovic M , Bisenic V , Milasinovic G 
Published: May 2024

Abstract

Background
Chronic right ventricular (RV) pacing can cause cardiac systolic dysfunction and heart failure (HF), increased risk of HF hospitalization and adverse outcomes. In these patients upgrading to cardiac resynchronization therapy (CRT) may improve left ventricular function.

Purpose
We aimed to identify the profile of patients (their clinical, electrical and echocardiographic characteristics) who are more likely to make a significant change in left ventricular ejection fraction (LVEF) one year after revision of the RV pacing system to CRT.

Methods
This was a retrospective, observational, single-center study. We included patients with a permanent antibradycardia pacemaker who had no systolic dysfunction and HF symptoms at the time of pacemaker implantation and who experienced a drop in LVEF below 35% during follow-up, with development of HF symptoms and with at least 20% of ventricular pacing. In all patient's revision to CRT was performed at our center between January 2014 and December 2019. We excluded patients who were indicated for a system upgrade regardless of the percentage of ventricular pacing and those in whom the drop in LVEF is due to a new coronary event. We used patients’ medical records to collect data on baseline characteristics. LVEF was measured pre-revision and 12 months after upgrade. To examine the difference in LVEF change between specified subgroups of patients we used a t-test.

Results
During the defined period, 82 upgrade procedures from conventional pacemaker to CRT were done in our center. We excluded 12 patients with left bundle branch block (LBBB) QRS morphology, 4 with non-LBBB QRS morphology but with QRS duration over 150ms and 4 patients who died within a year after revision to CRT. Therefore, we analyzed 62 patients (20.9% female, mean age 66.9 ± 11.2 years, mean LVEF 25.9 ± 6.8). After 12 months, 58.1% of patients had an increase in EF above 5%, and the mean change in LVEF (ΔLVEF) was 7.8 ± 11.8. Compared to those with non-ischemic cardiomyopathy (NICMP), patients with ischemic etiology had statistically significantly less improvement in LVEF (ΔLVEF 1.8 ± 6.8 vs 13.1 ± 12.7, p &lt; 0.01), as well as patients with an RV apical pacing compared to those with a septal lead position (ΔLVEF 5.1 ± 9.1 vs 14.1 ± 14.7, p = 0.021). Patients with narrower paced QRS complex (&lt;150ms) before upgrade had a significantly greater improvement in LVEF compared to those with a wider paced QRS complex (≥150ms) (ΔLVEF 10.9 ± 12.2 vs 4.8 ± 10.7, p = 0.04), and those with post-revision paced QRS width above 150ms had significantly lower change in LVEF compared to those with a narrower paced QRS (ΔLVEF 4.6 ± 9.8 vs 11.1 ± 12.8, p = 0.028).

Conclusion
Patients with NICMP and with width of the paced QRS complex before and after revision to CRT below 150ms had significantly greater improvement in LVEF 12 months after the upgrade. The position of RV lead significantly affects the success of the upgrade procedure.