Acute effects of interruption of cardiac resynchronization therapy on left ventricular morpho-functional parameters as assessed by cardiac magnetic resonance
Authors: Basile C , Scatteia A , Gallo P , Pezzullo S , Mancusi C , Pascale C E , Perrone-Filardi P , Paolillo S , Dellegrottaglie S 
Published: June 2023

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Cardiac resynchronization therapy (CRT) has become a standard treatment for patients with heart failure with reduced ejection fraction (HFrEF) and left ventricular (LV) dyssynchrony. Both immediate and long-term clinical and functional improvement have been reported after CRT implementation, as well as a decrease in the mortality and hospitalization rates. Recently, it has been questioned whether, once LV function has improved and reverse LV remodeling has occurred, ongoing biventricular pacing is still necessary.

Purpose
To assess by cardiac magnetic resonance (CMR) the acute effect on LV systolic function and dimensions of discontinuing CRT in patients with HFrEF.

Methods
The study prospectively included a small cohort of patients with HFrEF (7 males and 1 female; mean age 63.7 ± 2.5 years; ischemic etiology in 50%) receiving an MR-conditional CRT device in accordance with the existing guidelines. CMR examinations have been performed before (pre-CRT) and after 6 months after CRT implantation (post-CRT). Each follow-up CMR study included two full sets of cine images for the evaluation of LV systolic function and volumes obtained, respectively, before (post-CRTON) and after (post-CRTOFF) disabling the CRT function on the device. To warrant patient safety, each post-CRT CMR study was performed following institutional protocols based on specific guidelines for patients with MR-conditional cardiac implantable electronic devices (CIEDs).

Results
No adverse events or significant changes in the CIEDs parameters (including pacing and sensing thresholds and battery level) were recorded during the follow-up CMR studies. At post-CRT evaluation, CMR image quality was judged to be at least sufficient for analysis in all patients. As compared with the basal pre-CRT study, a significant increase in LVEF was detected at the post-CRTON CMR evaluation (28,1 vs 35,0%; p &lt;0,05) (Figure 1), together with a clear trend towards a decrease in LV end-diastolic volume [LVEDV] (118.72 ± 11.00 mL vs. 107.5 ± 13.86 mL; p = n.s) and LV end-systolic volume [LVESV] (87.12 ± 9.40 mL vs. 71.125 ± 11.26 mL; p = n.s.) (Figure 2). No relevant changes were detected when re-assessing the same LV parameters by CMR immediately after switching off the CRT function (post-CRTOFF study), with persisting increase in LVEF (37.9 ± 4.5%; p &lt;0,05 vs. pre-CRT) and tendency towards decreased LVEDV (97.3 ± 12.3 mL; p = n.s. vs. pre-CRT) and LVESV (63.0 ± 11.4 mL; p = n.s. vs. pre-CRT).

Conclusion
These preliminary findings show that favorable changes induced on LV function and remodeling by prolonged CRT in HFrEF patients are not promptly lost after the interruption of the electrical therapy. Whether a longer CRT interruption would determine more pronounced variations in the LV parameters or if the effects of CTR discontinuation may be related to the effective length of the period of time between implantation and cessation of the therapy deserve further investigation.