title: Nonspecific intraventricular conduction delay: Definitions, prognosis, and implications for cardiac resynchronization therapy.
abstract: Cardiac resynchronization therapy (CRT) is an electrical treatment of heart failure with reduced ejection fraction and wide QRS. It aims to correct the electrical dyssynchrony present in 30% to 50% of patients in this population. Dyssynchrony results in widening of the QRS complex on the electrocardiogram (ECG). CRT was initially developed to treat patients who had left bundle branch block (LBBB) and delayed activation of the lateral left ventricular wall. However, a large proportion of heart failure patients present with a widened QRS that is neither an LBBB nor a right bundle branch block (RBBB): nonspecific intraventricular conduction delay (NICD). Less studied than RBBB or LBBB, its pathophysiology is both complex and varied yet still reflects intramyocardial conduction delay. NICD is most often associated with cardiomyopathy (eg, ischemic or hypertensive). Conduction pathways can be either healthy or affected. Results from CRT are contradictory in this patient group, despite a seemingly neutral trend. Unfortunately, prospective studies are lacking. Guidelines recommending implantation of CRT devices in this group are based solely on analyses of subgroups with small sample sizes. A dedicated prospective study is therefore warranted for this question to be answered properly. A detailed study of the ECG and noninvasive study of ventricular electrical activation may enable clinicians to better identify patients with NICD who will respond to CRT.
authors.affiliation: Hôpital Cardiologique du Haut-Lévêque, CHU Bordeaux, Université Bordeaux, IHU LIRYC, Bordeaux, France; Clermont Université, Université d'Auvergne, Cardio Vascular Interventional Therapy and Imaging, Image Science for Interventional Techniques, UMR6284, and CHU Clermont-Ferrand, Cardiology Department, F-63003 Clermont-Ferrand, France. Electronic address: reschalier@chu-clermontferrand.fr.
authors.forename: Romain
authors.initials: R
authors.lastname: Eschalier
authors.affiliation: Hôpital Cardiologique du Haut-Lévêque, CHU Bordeaux, Université Bordeaux, IHU LIRYC, Bordeaux, France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Ploux
authors.affiliation: Hôpital Cardiologique du Haut-Lévêque, CHU Bordeaux, Université Bordeaux, IHU LIRYC, Bordeaux, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Ritter
authors.affiliation: Hôpital Cardiologique du Haut-Lévêque, CHU Bordeaux, Université Bordeaux, IHU LIRYC, Bordeaux, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Haïssaguerre
authors.affiliation: VCU Pauley Heart Center, Medical College of Virginia/VCU School of Medicine, Richmond, Virginia.
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Ellenbogen
authors.affiliation: Hôpital Cardiologique du Haut-Lévêque, CHU Bordeaux, Université Bordeaux, IHU LIRYC, Bordeaux, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Bordachar
mesh_terms: D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy / Q000379:methods; D004562:Electrocardiography / Q000379:methods; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D017410:Practice Guidelines as Topic; D011379:Prognosis
keywords: Cardiac resynchronization therapy; Nonspecific intraventricular conduction delay; Prognosis; QRS morphology