title: Limitation of the atrial extrastimulus technique for assessment of the His-Purkinje system in patients with right bundle branch block.
abstract: A prospective study of the usefulness of the atrial extrastimulus technique for assessment of the His-Purkinje system was undertaken in 19 consecutive patients with complete RBBB and an abnormal or indeterminate frontal QRS axis. A total of 59 basic cycle lengths (BCLs) could be analyzed in detail. The most common patterns of His-Purkinje conduction seen were simple linear (V1V2 vs H1H2, N = 49) or flat (H2V2 vs H1H2, N = 44) curves. This finding is related to the limitation imposed by interposition of the slowly conducting AV node between the site of the extrastimulus and the His-Purkinje system. One or more refractory periods could be measured in only 27% of BCLs (10 Effective Refractory Periods of the remaining intact His-Purkinje system plus 16 Functional Refractory Periods and 19 Relative Refractory Periods). No refractory periods of the His-Purkinje system could be determined in 8 of 19 patients (42%), the major limitation being slowed AV node conduction. The results suggest limited likelihood that additional clinically useful information about His-Purkinje system conduction can be obtained by the atrial extrastimulus technique, as used in this study, although it may be helpful in assessing other parts of the conduction system.
mesh_terms: D000328:Adult; D000368:Aged; D002036:Bundle of His / Q000503:physiopathology*; D002037:Bundle-Branch Block / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011690:Purkinje Fibers / Q000503:physiopathology*; D012032:Refractory Period, Electrophysiological