Predicting Ventricular Arrhythmic Risk in Non-Ischemic Cardiomyopathy: A Comparative Study of Late Gadolinium Enhancement and Grey Zone Scar Techniques (RF_TH_255)

Myocardial scar is associated with arrhythmic events in non-ischemic cardiomyopathy (NICM),¹ but the role of the "grey zone" remains unclear. Various methods exist to quantify scar tissue,² but it's unknown which best predicts arrhythmic events in this population.

This study aimed to determine the most adequate quantitative method of myocardial scar assessment, including the "grey zone", using CMR to predict ventricular arrhythmias.³


Methods:

This was a single-centre retrospective study that included patients with NICM and a CMR with visually assessed late gadolinium enhancement (LGE). Quantitative analysis was performed by measuring LGE mass (absolute and relative to the total myocardial mass, in percentage), grey zone scar (GZS) and total scar (TS) masses. LGE was assessed with the reference region of interest (ROI) method (intensity 5 standard deviations [5SD] above remote myocardium), the full width at half maximum (FWHM) and manually selected single intensity threshold. GZS was defined as non-LGE area with intensity above 2SD or 3SD above the reference ROI mean. Total scar (TS) was defined as the total mass with intensity above 2SD of reference ROI.

Two composite endpoints were selected: 1) Major Ventricular Arrhythmic Event (MVAE) was defined as sudden cardiac death (SCD), appropriate implantable cardioverter-defibrillator (ICD) shock, ventricular fibrillation (VF) or sustained ventricular tachycardia (SVT) and 2) Total Ventricular Arrhythmic Events (TVAE), including MVAE and, additionally, non-sustained ventricular tachycardia (NSVT).


Results:

This cohort included 143 NICM, LGE-positives patients, mean age of 65.6 ± 12.4 years, male sex (82%), mean indexed left ventricular end-diastolic volume (LVEDVi) 120.6 ± 39.2 mL, and mean left ventricular ejection fraction (LVEF) of 32.7 ± 11.2%.

After 5.3 [IQR 3.9-6.8] years, TVAE and MVAE endpoints occurred in 35 (24.5%) and 15 (10.5%) patients, respectively.

Most of myocardial scar quantitative mass measures were predictive of both MVAE and TVAE. Variables with the highest discriminative value, according to Harrel’s C index, for the TVAE were 5SD-LGE (HR 1.03 [1.02-1.05], p = < 0.001, C-index 0.6315), 2SD-GZS (HR 1.03 [1.01- 1.05], p = 0.015, C-index 0.631) and TS (HR 1.02 [1.01-1.03], p = < 0.001, C-index 0.631). For MVAE, 5-SD LGE had a similar association compared with TVAE (C-index 0.667); whereas both 2SD-GZS and TS had a stronger association (C-index 0.737 and 0.721, respectively) (Table 1 and Figure). To note, 5SD-LGE relative mass was not statistically significant for MVAE (Table 1).

It's also important to highlight that, while FWHM and manual single threshold LGE quantification showed no significant correlation with arrhythmic endpoints, TS and every GZS quantification, regardless the LGE quantification method included, were predictors of both MVAE and TVAE (Table 1).

Finally, in a multivariate analysis adjusted for other well-known clinically prognostic functional measures, such as LVEF, LVEDVi and LV global longitudinal strain (LV-GLS), 5SD-LGE, 2SD-GZS and TF were independently associated with both MVAE and TVAE (Table 2).⁴


Conclusion:

The quantification of myocardial scar in patients with NICM and LGE, including grey zone analysis as absolute mass values, showed a stronger predictive value for MVAE compared to LGE percentage alone. Moreover, the absolute masses from grey zone analysis and total scar tissue, along with 5SD-LGE, were linked to a higher risk of MVAE and TVAE, independently of LVEF, LVEDVi, and LV-GLS.