Open AccessElectrophysiologic significance of leftward qrs axis deviation in bifascicular and trifascicular blocks
Author(s) -
Ducceschi Valentino,
Sarubbi Berardo,
D'Andrea Antonello,
Liccardo Biagio,
Lucca Pasqualina,
Mayer Maria Serena,
Scialdone Antonino,
Santangelo Lucio,
Iacono Aldo
Publication year - 1998
Publication title -
clinical cardiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.263
H-Index - 72
eISSN - 1932-8737
pISSN - 0160-9289
DOI - 10.1002/clc.4960210809
Subject(s) - medicine , left axis deviation , qrs complex , cardiology , left bundle branch block , intraventricular conduction , electrical conduction system of the heart , bundle branch block , electrocardiography , right bundle branch block , heart failure
Background : Intraventricular conduction disturbances determine complete impairment of impulse propagation along the right or left bundle branch or the two left fascicles. Hypothesis : This study was undertaken to investigate the electrophysiologic significance of QRS axis (QRSA) orientation in bifascicular and trifascicular blocks. Methods : A group of 76 subjects, 43 with right bundle‐branch block (RBBB) and left anterior hemiblock (LAH) (Group A), and 33 with left bundle‐branch block (LBBB) (Group B) was submitted to electrophysiologic evaluation. Results : In Group A, QRSA was inversely related only to intraventricular conduction, while in Group B, QRSA inversely related to infrahisal conduction times. A value of <60° was considered the cut‐off point for determin‐ing subjects with a considerable leftward QRSA deviation. Of the 27 Group A patients with a QRSA <‐60°, 38.5% developed an infrahisal second‐degree atrioventricular (AV) block during incremental atrial stimulation (IAS) in comparison with 11.1 % of those with QRSA >‐60°. Of the 9 Group B patients with a QRSA <‐60°, 44.4% exhibited severe impairment of infrahisal conduction at baseline and 66.6% developed an infrahisal second‐degree AV block during IAS, whereas among the remaining 24 with a QRSA >60°, in only 8.3% were both infrahisal (HV1 and HV2) intervals dangerously prolonged, and 23.8% encountered an infrahisal second‐degree AV block during IAS. In Group A, atrioventricular conduction time >200 ms exhibited a better predictive accuracy than QRSA <60° for the development of an infrahisal second‐degree AV block during IAS, whereas the latter appeared the best noninvasive predictor in Group B with a slightly lesser predictive accuracy than HV >80 ms. Conclusion : The degree of leftward QRSA deviation seems to reflect the entity of intraventricular conduction delay in patients with RBBB + LAH, while it appears to be directly related to infrahisal conduction prolongation in those with LBBB.