Long-term prognostic role of pre-ICD implantation magnetic resonance: a longitudinal cohort study
Authors: Spoladori M , Crocamo A , Capoccia F , Rizzello D , Vrenozaj R , Bettella A , Cavalli S , De Maria M , Zilioli C , Bearzot L , Gonzi G L , Palumbo A A , Niccoli G , Ardissino D , Notarangelo M F 
Published: May 2024

Abstract

Background
While it's has already been demonstrated that cardiovascular mortality increases in patients with reduced ejection fraction (EF), there is no evidence that this parameter identifies with high sensitivity those who will experience sudden cardiac death (SCD). Cardiac magnetic resonance (CMR), through myocardial scar characterization, could enhance risk stratification for arrhythmic events in such patients.

Purpose
The study's objective was to identify factors, independent of EF, capable of stratifying arrhythmic risk in a population of patients undergoing implantable cardioverter-defibrillator (ICD) placement.

Methods
This is an observational, retrospective, longitudinal, cohort study. Demographic, clinical, and radiological data were collected for all patients undergoing ICD implantation between 2014 and 2021. Deaths from all causes and significant arrhythmic events (non-sustained ventricular tachycardia, sustained ventricular tachycardia, ventricular fibrillation) were recorded during routine device controls and remote monitoring. To define the prognostic value of various factors was performed an univariate Kaplan-Meier analysis in relation to the composite primary endpoint, consisting of ventricular arrhythmias [VA] and all-cause mortality.

Results
Among 700 patients (82% males, mean age 69 ± 13 years) who underwent ICD implantation (46% single-chamber, 15% dual-chamber, 36% cardiac resynchronization therapy, 3% subcutaneous ICD) pre-implantation CMR was available in 354 of the total, with 69% of them implanted for primary prevention and 52% with non-ischemic cardiomyopathy. Late gadolinium enhancement (LGE) was present in 67% of them; and 30% of these patients had it in fewer than 5 segments. At the end of the mean 8-year follow-up, 30.6% of patients died. Patients with LGE showed increased all-cause mortality and incidence of VA compared to those without LGE (HR=2.17 [1.78-2.60]; p&lt;0.05); this data was mainly driven by the difference in mortality, as the incidence of VA alone did not exhibit significant variation between the two groups (HR=0.7 [0.65-1.02]; p=0.23). In patients with fewer than 5 cardiac segments involved by LGE, the risk of all-cause death and significant VA was higher than in those with more than 5 segments involved (HR=2.46 [2.09-9.07]; p&lt;0.05).

Conclusions
The presence of LGE emerged as a significant prognostic factor for both arrhythmic events and overall mortality. This suggests the possibility that assessing myocardial fibrosis serves as a comprehensive predictor of the patient's future clinical outcome, extending beyond merely predicting arrhythmic events. Notably, the relevance of LGE is heightened when observed in fewer than 5 segments, indicating a focal substrate, making it a crucial prognostic factor for anticipating arrhythmic events. In patients with reduced EF, pre-implantation CMR proves valuable in effectively stratifying arrhythmic risk and all-cause mortality.