Quantification of late-gadolinium enhancement magnetic resonance imaging to predict ventricular arrythmias and sudden cardiac death: A systematic review

Late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (CMR) is a recognized tool for identifying myocardial fibrosis in non-ischemic cardiomyopathy (NICM). Myocardial fibrosis is associated with ventricular arrhythmias (VA) and sudden cardiac death (SCD). However, inconsistent methods for LGE quantification and lack of consensus in defining significant fibrosis limit its interpretation and use for risk stratification. Adding to the complexity, due to the absence of fully automated quantification methods, the inherent subjectivity of LGE interpretation poses challenges, but remains pivotal in guiding life-saving primary prevention treatment such as implantable cardioverter defibrillators (ICD).

The purpose of this study is to summarize current knowledge regarding LGE quantification methods used in NICM and evaluate their predictive value for VA.

A systematic review of observational studies was conducted to evaluate the association between LGE, as measured through CMR, and the risk of VA in NICM patients. Ventricular arrhythmias were defined as SCD, ventricular tachycardia, ventricular fibrillation, aborted SCD, or appropriate ICD intervention. Data extraction was performed by two reviewers, with discrepancies resolved by consensus. Summary statistics were pooled, and figures constructed to show LGE variability and its link to VA risk.

From an initial screening of 1,077 studies, 35 studies involving a total of 12,286 NICM patients were identified. The two main methods for quantifying LGE were standard deviation (SD) thresholding (20 studies) and the Full Width Half Maximum (FWHM) method (15 studies). The LGE volume or mass varied between studies and quantification methods. Lower thresholds (e.g., 2 SD) identified larger LGE volumes, while higher thresholds (e.g., 5-6 SD) reported smaller volumes. Regardless of the quantification method used, the hazard ratio (HR) ranged between 1.04 to 1.29 per % increase of LGE. Similarly, presence of LGE, particularly in the septal and midwall regions, was consistently linked to an increased risk of VA.

LGE presence, extent, and specific locations are consistently associated with VA in NICM, with septal or midwall LGE conferring higher risk. However, LGE extent depends, among other factors, on the quantification method used, excluding uniform thresholds for risk prediction in NICM. Standardized quantification methods, larger-scale studies with external validation, and further investigation into the prognostic value of specific LGE parameters are crucial for advancing this field and improving patient care.

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