title: Delay and block of cardiac impulse caused by enhanced phase-4 depolarization in the His-Purkinje system.
abstract: The underlying mechanism of bradycardia-dependent bundle-branch and paroxysmal atrioventricular block appears to be enhancement of phase-4 depolarization in a branch or in a natural or acquired monofascicular pathway. Clinical records of these forms of impaired conduction occurring in the bundle-branches, with either longer or shorter cardiac cycle lengths, are presented and analysed. These also include the combination of Mobitz typw I atrioventricular block with variable degrees of bundle-branch block, as a representative example of narrow ventricular escape beats firing in the zone where prominent diastolic depolarization is present.
mesh_terms: D000219:Adams-Stokes Syndrome / Q000150:complications; D000328:Adult; D000368:Aged; D000787:Angina Pectoris / Q000150:complications; D001018:Aortic Diseases / Q000150:complications; D001919:Bradycardia / Q000503:physiopathology*; D002036:Bundle of His / Q000503:physiopathology; D002037:Bundle-Branch Block / Q000150:complications / Q000503:physiopathology; D006328:Cardiac Catheterization; D006332:Cardiomegaly / Q000150:complications; D004562:Electrocardiography; D005260:Female; D006327:Heart Block / Q000150:complications / Q000503:physiopathology*; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008564:Membrane Potentials; D008875:Middle Aged; D011690:Purkinje Fibers / Q000503:physiopathology; D014672:Vectorcardiography