title: Nodal and infranodal atrioventricular conduction block: electrophysiological basis to correlate the ECG findings.
abstract: A 68-year-old woman with a history of dilated non-ischemic cardiomyopathy presented with syncope. The index ECG showed sinus rhythm with left bundle branch block. On telemetry episodes of sinus rhythm with narrower QRS complexes conduced in 2:1 pattern were noted. Invasive electrophysiological study was performed to determine cause of syncope. Normal conduction up to the AV node with an AH interval of 79 ms (normal = 55-125 ms) was observed. However, every alternate sinus beat was blocked after the inscription of His deflection (infra-Hisian block). The narrow beats conducted through the His bundle with HV intervals of 54 ms (normal = 35-55 ms). When 1:1 conduction resumed further abnormality of the His-Purkinje conduction system became evident with a QRS morphology that of an LBBB and prolongation of HV interval (HV = 96 ms). Criteria to differentiate nodal versus infranodal block based on electrophysiological properties of the nodal and infranodal system are discussed.
authors: Professor of Medicine, The University of Texas-Health Science Center at Houston, 6431 Fannin Street, Suite MSB 1.246, Houston, TX 77030, USA; Director, Clinical Cardiac Electrophysiology Fellowship Training Program, 6431 Fannin Street, Suite MSB 1.246, Houston, TX 77030, USA; Director, Cardiac Electrophysiology Laboratories-Memorial Hermann Hospital, 6431 Fannin Street, Suite MSB 1.246, Houston, TX 77030, USA. Electronic address: bharat.k.kantharia@uth.tmc.edu.
authors: Bharat K
authors: BK
authors: Kantharia
authors: Arti N
authors: AN
authors: Shah
mesh_terms: D000368:Aged; D054537:Atrioventricular Block / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D006801:Humans