Cardiac Magnetic Resonance as a Tool to Assess Dyssynchrony

Cardiac Resynchronization Therapy in Non-Ischemic Cardiomyopathy: Role of Multimodality Imaging

Non-ischemic cardiomyopathy encompasses a heterogeneous group of diseases, with a generally unfavorable long-term prognosis. Cardiac resynchronization therapy (CRT) is a useful therapeutic option for patients with symptomatic heart failure, currently recommended by all available guidelines, with outstanding benefits, especially in non-ischemic dilated cardiomyopathy. Still, in spite of clear indications based on identifying a dyssynchronous pattern on the electrocardiogram (ECG,) a great proportion of patients are non-responders. The idea that multimodality cardiac imaging can play a role in refining the selection criteria and the implant technique and help with subsequent system optimization is promising. In this regard, predictors of CRT response, such as apical rocking and septal flash have been identified. Promising new data come from studies using cardiac magnetic resonance and nuclear imaging for showcasing myocardial dyssynchrony. Still, to date, no single imaging predictor has been included in the guidelines, probably due to lack of validation in large, multicenter cohorts. This review provides an up-to-date synthesis of the latest evidence of CRT use in non-ischemic cardiomyopathy and highlights the potential additional value of multimodality imaging for improving CRT response in this population. By incorporating all these findings into our clinical practice, we can aim toward obtaining a higher proportion of responders and improve the success rate of CRT.

Fibrosis and Ventricular Arrhythmogenesis: Role of Cardiac MRI

Cardiac fibrosis is a significant increase in collagen volume fraction of myocardial tissue. It plays an important role in the pathophysiology of many cardiovascular abnormalities. Electrophysiologically, myocardial fibrosis produces anisotropic conduction, inhomogeneity, and conduction delay. Several markers are available to detect myocardial fibrosis. CMRI is the most common imaging technique; late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) provides markers for tissue characterization, disease progression and arrhythmic events. LGE-CMR can be used as risk marker of occurrence of pathologic conditions. LGE-CMR demonstrates specific patterns related to different pathologic substrates. We discuss the role of CMRI in ventricular arrhythmogenesis.

The Past, Present and Future of Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) has revolutionized the care of the patients with heart failure with reduced ejection fraction and electrical dyssynchrony. The current guidelines for patient selection include measurement of left ventricular systolic function, QRS duration and morphology, and functional classification. Despite consistent and increasing evidence supporting CRT use in appropriate patients, CRT has been underutilized. Notwithstanding the heterogeneous definitions of non-response, more than one-third of patients demonstrate a lack of echocardiographic reverse remodeling or poor clinical outcome following CRT. Since the causes of this non-response are multifactorial, it will require multidisciplinary efforts to overcome including optimal patient selection, procedural strategies, as well as optimizing post-implant care in patients undergoing CRT. The innovations of novel pacing approaches combined with advanced imaging technologies may eventually offer a personalized CRT system uniquely tailored to each patient's dyssynchrony signature.