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

Abstract

The mechanisms of aberrant conduction at the onset of induced orthodromic tachycardia in the Wolff-Parkinson-White syndrome were analyzed in 20 consecutive patients in whom this tachycardia was initiated by the atrial (A2) and/or right ventricular (V2) extrastimulus techniques. Of 13 patients in whom orthodromic tachycardia was induced by the A2 method, functional right bundle branch block occurred at tachycardia onset in four (31%) and left bundle aberrancy in two (15%), one of whom also manifested right bundle aberrancy. The occurrence of bundle branch block at the onset of tachycardia was linked to aberrant conduction of the initiating A2 impulse which, in turn, was associated with attainment of relatively short HisHis2 intervals within the tachycardia initiation zone. Aberrant conduction of A2 was also more common in patients without manifest preexcitation. In contrast, of 14 patients in whom orthodromic tachycardia was induced by the V2 method, left bundle aberrancy occurred at the onset of tachycardia in 11 (79%), one of whom manifested right bundle branch block as well. Left bundle aberrancy was more likely to occur when the interval from the initiating V2 (or macro-reentrant V3) impulse to the first anterograde His deflection was <300 ms. This suggests that left bundle aberrancy at the onset of orthodromic tachycardia induced by the V2 method results from concealed retrograde penetration of the HisPurkinje system, with the left bundle being last to recover. Our findings provide the conceptual basis for a physiologic approach to the deliberate induction of specific types of aberrant conduction at onset of orthodromic tachycardia in patients with Wolff-Parkinson-White syndrome.

Almokalant—A Selective Class III Antiarrhythmic Compound

“…Despite this, almokalant induced both bundle-branch block (BBB) and AV block during induced supraventricular tachycardia (23,28). Fourteen of the observed BBB morphologies were left sided and 8 were right sided, a distribution similar to what has been observed in the drug-free condition (18,40). Prognostic factors for the development of BBB were: rapid rate of the baseline tachycardia, the number of previously induced tachycardias during the procedure, and the almokalant dose (23,28).…”

Transition from Narrow to Wide QRS Tachycardia: What is the Mechanism?

“…Importantly, the cycle length of the tachycardia is the same during the narrow and wide QRS complex tachycardias. Also, aberrant conduction is often seen at the onset of induced tachycardia and later may resolve, 1 opposite to what is seen in Figure 1. The morphology during wide QRS shows right bundle branch block with left-axis deviation.…”

Functional Bundle Branch Block as a Delayed Manifestation of Retrograde Concealment in the His‐Purkinje System

“…Likewise, the twrizontat bars represent the activation cycte tengths (CL) of the segments 1-4 from the time that BBR is generated to ttie time that the ftrst tachycardia complex (SVT-l) is conducted. Note that among different .segments of the bundle branches including pro.\imat teft tnmdie (I), proximal right bundle (2). di.stal right bundte (3).…”