Arrhythmic risk stratification by cardiac magnetic resonance tissue characterization: disclosing the arrhythmic substrate within the heart muscle

Abstract

Sudden cardiac death (SCD) is a pivotal health problem worldwide. The identification of subjects at increased risk of SCD is crucial for the accurate selection of candidates for implantable cardioverter defibrillator (ICD) therapy. Current strategies for arrhythmic stratification largely rely on left ventricular (LV) ejection fraction (EF), mostly measured by echocardiography, and New York Heart Association functional status for heart failure with reduced EF. For specific diseases, such as hypertrophic and arrhythmogenic cardiomyopathy, some risk scores have been proposed; however, these scores take into account some parameters that are a partial reflection of the global arrhythmic risk and show a suboptimal accuracy. Thanks to a more comprehensive evaluation, cardiac magnetic resonance (CMR) provides insights into the heart muscle (the so-called tissue characterization) identifying cardiac fibrosis as an arrhythmic substrate. Combining sequences before and after administration of contrast media and mapping techniques, CMR is able to characterize the myocardial tissue composition, shedding light on both intracellular and extracellular alterations. Over time, late gadolinium enhancement (LGE) emerged as solid prognostic marker, strongly associated with major arrhythmic events regardless of LVEF, adding incremental value over current strategy in ischemic heart disease and non-ischemic cardiomyopathies. The evidence on a potential prognostic role of mapping imaging is promising. However, mapping techniques require further investigation and standardization. Disclosing the arrhythmic substrate within the myocardium, CMR should be considered as part of a multiparametric approach to personalized arrhythmic stratification.

Endomyocardial biopsy in the clinical context: current indications and challenging scenarios

“…Conversely, a family history of HCM or sudden death at a young age, significant cardiac hypertrophy with an asymmetrical pattern, especially involving the interventricular septum or the apex, and the identification of a genetic mutation in sarcomeric proteins suggest the presence of HCM. CMR can provide important information to differentiate HCM from phenocopies [ 3 ], but a final diagnosis can be made only by histological analysis in specific settings.…”

“…Indeed, along with a full morphological and functional cardiac assessment, CMR imaging can provide a detailed characterization of the cardiac muscle composition, although it may not be feasible in patients with specific features (i.e. arrhythmias, poor breath-holding, non-conditioned cardiac devices) [ 3 ]. A remarkable example is the possibility to reach a non-invasive diagnosis of acute myocarditis (AM), according to the Lake Louise Criteria published in 2009 [ 4 ], updated in 2018 [ 5 ].…”

Standardizing the role of endomyocardial biopsy in current clinical practice worldwide

“…sarcoidosis or myocarditis) to guide the best cardiac site and ventricle for EMB 5 . Pre‐operative imaging may identify the sites with myocardial fibrosis (CMR LGE and T1 mapping), cardiac oedema and inflammation (CMR T2 mapping and 18F‐FDG PET) 1 and the use of intra‐procedural electroanatomic mapping may detect ventricular segments with fragmented or low voltages 5 . Although these findings are not disease‐specific and reflect common responses to myocardial injury, they might help in selecting the best cardiac chamber (left vs. right ventricle) and site (most diseased area) for sample collection 5 and minimize the risk of complications with patient‐tailored pre‐procedural planning.…”

“…In recent years, the use of advanced imaging modalities, including echocardiography with three‐dimensional and myocardial strain analysis, cardiac magnetic resonance (CMR) and positron emission tomography (PET), has revolutionized the non‐invasive approach to diagnosis and prognostic stratification of cardiac diseases. Along with a full morphological and functional cardiac assessment, CMR imaging provides in vivo characterization of the cardiac muscle composition 1 . In particular, the presence of late gadolinium enhancement (LGE) revealing myocardial fibrosis, the development of quantitative parameters (mapping technique) and extracellular volume (ECV) exploring the myocardial interstitium, 1,2 significantly restricted the role of endomyocardial biopsy (EMB) for the evaluation of heart diseases.…”

CMR-Based Risk Stratification of Sudden Cardiac Death and Use of Implantable Cardioverter–Defibrillator in Non-Ischemic Cardiomyopathy

“…When compared to CMR, the advantages of echocardiography remain the costeffectiveness, higher availability, and the usability irrespective of renal function or cardiac devices affecting image quality [83,84]. However, inter-observer variability was lower in CMR [83].…”