Evolution of surface and endocavitary signals in patients with arrhythmogenic cardiomyopathy at 1 and 5 years
Authors: Martignani C , Spadotto A , Graziosi M , Massaro G , Pollini C , Angeletti A , Ziacchi M , Biagini E , Biffi M , Diemberger I 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: Private company. Main funding source(s): Small fee from Boston Scientific.

Background
The use of subcutaneous defibrillator (S-ICD) is a viable alternative to transvenous ICD in patients with Arrhythmogenic Cardiomyopathy (ACM). In transvenous ICD recipients low sensing values may exist at the time of implantation and a progressive decline of signal amplitude may occur later on due to the progressive myocardial fibrofatty replacement. Similarly to what happens at the intracavitary level, in patients with ACM there is a progressive modification of the surface ECG over time. Data on the impact of ECG evolution on S-ICD sensing are still lacking, particularly for different ACM phenotypes.

Purpose
This study aims to analyze the evolution of surface electrocardiogram (ECG), focusing on R-wave amplitude variation, and intracavitary electrograms (EGMs) in ACM different phenotypes during a 1-year and a 5 five-year follow-up.

Methods
This study is a retrospective analysis of the data of consecutive patients with ACM who were referred to our centre from January 1992 to October 2021. Using a dedicated software, the ECG analysis was performed in 7 leads: DI, DII, aVF (in view of the similar orientation with the three S-ICD vectors) and V1, V2, V3 and V5.

Results
We included 69 ACM patients: 28 patients (41%) had a right ventricular involvement (ARVC), 19 (27%) had a dominant LV involvement (ALVC) and 22 (32%) had biventricular involvement. 58 patients (84%) were ICD recipients; 45/58 patients (78%) had a transvenous ICD, and 13/58 (22%) had an S-ICD. During 5-year follow-up, in the whole ACM population, there were no significant changes in the amplitude of the R-wave, S-wave and T-wave. Phenotypic subgroups showed a different R-wave amplitude at baseline: biventricular ACM and ALVC patients had a lower R-wave amplitude in DII (p=0.04; p=0.05) and aVF (p=0.01; p=0.01) compared to ARVC patients. However, within each group, no difference was observed in R-wave amplitude at 1 and 5 years compared to baseline ECG (Figure 1). In the transvenous ICD recipients (45/69 patients) mean sensing decreased progressively over time (9,38 ± 4,24 mV at baseline, 7,70 ± 2,91 mV at 1 year, 1,85 ± 6,86 mV at 5 years). The reduction was not statistically significant at the first year of follow-up (p=0.239) but it reached significance at 5 years (p&lt;0.001). Patients with biventricular ACM had lower sensing values at baseline than ARVC and ALVC (p&lt;0,001). Sensing values in the biventricular patients did not decrease significantly during the 5-year follow-up (p=0.21), whereas in the ARVC and ALVC groups a reduction in sensing values was observed albeit not statistically significant in ALVC (p=0.01 in ARVC and p =0.06 in ALVC) (Figure2).

Conclusions
These data suggest that surface ECG may be more stable over time compared to EGM, therefore if a patient is suitable for S-ICD implantation S-ICD sensing may remain stable over time. Despite these findings, further studies are needed to support these hypotheses.