Effects of alternating cycle lengths on refractoriness of the His-Purkinje system.

Abstract

A s bstract. The effects ofalternating cycle lengths (bigeminal rhythm) on His-Purkinje system refractoriness were studied in 14 patients using His bundle and right bundle recordings. Programmed atrial stimulation at constant cycle length (method I) was scanned using the atrial extrastimulus technique (A2) and compared with an atrial cycle length of identical duration coupled to A2 on alternate beats (method II). The results showed that (a) despite shorter cycle length ofthe His-Purkinje system with method II due to effect of A2 on atrioventricular nodal conduction (699±90 vs. 743±87 ms, P < 0.001), the relative refractory period of the His-Purkinje system was always longer with method II (463±52 vs. 440±43 ms, P < 0.001). A similar increase also occurred in effective refractory period of the His-Purkinje system; (b) while functional right bundle branch block occurred in eight patients and functional left bundle branch block in two patients with method I, functional right bundle branch block occurred in all 14 patients and left bundle branch block in seven patients with method II; (c) in two patients where both functional right and left bundle branch block occurred with method I this never was manifest at identical degree of abbreviation of His-Purkinje system cycle length but was manifest at identical abbreviation in each of seven patients with method II; (d) site of conduction delay and/or block during functional right bundle branch block was always proximal, i.e., between the His bundle and right bundle recordings with both methods. During method II this resulted in shortening of the subsequent right bundle cycle length relative to the subsequent His bundle (and of necessity left bundle) cycle length.

Electrophysiologic mechanisms of functional bundle branch block at onset of induced orthodromic tachycardia in the Wolff-Parkinson-White syndrome. Role of stimulation method.

“…Because aberrant conduction at onset of OT induced by the A2 method appears largely determined by the occurrence (and type) of fx BBB during anterograde propagation of A2, techniques that increase the "yield" of fx (usualy R) BBB during conduction of A2 should also facilitate occurrence of(R)BBB at OT onset. Such techniques might include not only use of both long and short basic cycle lengths (the latter being perhaps more likely to promote fx LBBB [20]) but also maneuvers that prolong His-Purkinje system refractoriness, such as abrupt short-to-long cycle length changes (21) and bigeminal rhythms (22).…”

Vulnerable Window for Conduction Block in a One-Dimensional Cable of Cardiac Cells, 2: Multiple Extrasystoles

“…Relevant to this observation, experimental studies have shown that dispersion of refractoriness, which correlates with the ventricular fibrillation threshold (2), is modulated by premature extrasystoles (3) and rapid heart rates (4,5). Other experiments (6)(7)(8)(9)(10)(11) have demonstrated that dispersion of refractoriness and inducibility of reentry are affected by the activation sequence of the premature extrasystoles. Previous computer simulation studies (12)(13)(14) have shown that the ability of a premature extrasystole to modulate dispersion of refractoriness depends on action potential duration (APD) restitution and conduction velocity (CV) restitution properties.…”

Evaluation of the input site and characteristics of the antegrade fast pathway based on three-dimensional bi-atrial stimulus-ventricle mapping

“…Here, the interval between the onset of the His bundle electrogram and peak of the QRS wave in lead II (c) was equivalent to the sum of the H-V interval and ventricular activation time (VAT: the time from the onset of the QRS wave to the peak of the R wave). The H-V interval and VAT are reported to have a very high reproducibility with minimal variability [7][8][9][10]. Therefore, the St-V map was considered an alternative to the St-H map.…”