Editorial for "Prognostic Value of Late Gadolinium Enhancement in Predicting Life‐Threatening Arrhythmias in Heart Failure Patients With Implantable Cardioverter‐Defibrillators"

Heart failure accounts for two-thirds of sudden death cases in the United States. The major cause of sudden death is ventricular arrhythmias (tachycardia and fibrillation). Ventricular arrhythmias occur in ischemic (ICM) and nonischemic cardiac myopathy (NICM). Life-threatening arrhythmia in ICM is associated with transmural infarct, myocardial fibrosis, and aneurysm, while the substrate for arrhythmia in NICM is myocardial inflammation, patchy embolization, and fatty/fibrous degeneration. In 2010, major cardiac societies also focused on device therapy in patients with depressed ventricular function, spontaneous/inducible nonsustained ventricular tachycardia, and myocardial infarction. Clinical studies have shown that implantable cardioverter defibrillator (ICD) devices in heart failure patients can substantially reduce life-threatening arrhythmias, via defibrillation, and sudden cardiac death (SCD). Current diagnostic strategies in patients at risk of heart failure rely on reduced left ventricular ejection fraction (LVEF). While LVEF has been traditionally employed for diagnosis of this disease, recent work has questioned its utility as a means of categorizing heart failure. On the other hand, magnetic resonance imaging (MRI) has been found to be highly effective in assessing myocardial viability and LV function. Investigators used different types (extracellular, intravascular, and intracellular) of MR contrast media for characterizing myocardial viability, perfusion, and microvascular integrity. Currently, late gadolinium enhancement (LGE) MRI is the method of choice for detecting myocardial infarct (acute and chronic), peri-infarction zone, and microvascular obstruction zone. The differential enhancement of injured myocardium on LGE is attributed to the increase of extracellular volume (ECV) (as a consequence of loss of cellular membrane integrity), edema (as a consequence of a leakage of plasma macromolecules), and slow washin and washout of gadolinium-based contrast media. El Aidi et al indicated that patients with LGE have a high rate of adverse cardiovascular events. Furthermore, the presence of a microvascular obstruction zone in the core of acute infarct correlates well with heart failure, arrhythmia, and SCD. After recognition of the presence of a peri-infarct zone in preclinical MRI studies, Yan et al found that the larger peri-infarct zone is associated with higher mortality at follow-up, due to arrhythmia. The use of LGE-MRI has been widened to include patients with nonischemic heart diseases, such as dilated cardiomyopathy, myocarditis, amyloidosis, sarcoidosis, cardiac neoplasms, etc. Based on this background, Yue et al in this issue of the Journal of Magnetic Resonance Imaging presented an updated and first review on the prognostic value of LGE in predicting life-threatening arrhythmias in 3457 heart failure patients with an implanted ICD. LGE was positive in 1923 (55.6%) of ICM and NICM patients. Data analysis revealed that patients with LGE have a higher odds ratio of 5.12 and 5.16 for life-threatening arrhythmia and major adverse cardiovascular events (MACE), respectively. Furthermore, the data showed an odds ratio of 2.38 for cardiovascular mortality and 2.11 for all-cause mortality compared with those without LGE. Additionally, ICM and NICM patients with LGE had an increased life-threatening arrhythmia odds ratio of 4.60 and 5.24, respectively, and MACE of 4.72, and 4.71, respectively. It was concluded that the presence of LGE 1) worsens the prognosis for adverse cardiovascular events in both ICM and NICM patients who benefit from ICDs, and 2) provides important prognostic values. In this review, the investigators used the visibility of bright injured regions on LGE-MRI as a biomarker for predicting the endpoint of life-threatening arrhythmias in ICM and NICM. Additional data on the prediction of the endpoint of life-threatening arrhythmias could be obtained from quantification and mapping ECV on LGEMRI. The integration of existing functional, viability, and perfusion cardiac MRI sequences may also reveal an incremental