The Different Varieties of 2:1 Bundle Branch Block

Nau, Gerardo; Elizari, Marcelo V.; Rosenbaum, Mauricio B.

doi:10.1007/978-94-009-6781-6_25

Cited by 6 publications

(10 citation statements)

References 10 publications

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“…Theoretically, both hypotheses 1 and 2 are consistent with the ECG of Figure 1. Supernormal conduction, however, usually occurs with very short ventricular cycles, 5 whereas in this case RBBB alternans is associated with relatively long RR intervals (about 600 ms). In addition, supernormality does not account for perpetuation of 2:1 RBBB with slowing down of the rate from 135 (strip a ) to 100 bpm (strip b ).…”

Section: Discussionmentioning

confidence: 92%

“… Tachycardia‐dependent (phase‐3) bidirectional block. An impulse anterogradely blocked in the affected bundle branch (BB) cannot penetrate this in retrograde direction; as a consequence, the pathway benefits from a long time to recover excitability, and the ensuing impulse finds this BB in a nonrefractory state, being normally conducted 1–3,5 Tachycardia‐dependent (phase‐3) unidirectional (anterograde only) block, associated with supernormal conduction in the impaired BB 6–8 .…”

Section: Discussionmentioning

confidence: 99%

“…Each abnormally conducted impulse undergoes retrograde concealed conduction into the blocked BB (the so‐called “linking” phenomenon); 9,10 this postpones or “shifts to the right” the BB refractory period and its supernormal “window,” so that the ensuing impulse is allowed to fall within the early phase of improved BB responsiveness, being normally (or less abnormally) conducted 4,6,11 . Accordingly, BBB alternans results from improved conduction whenever a sinus impulse follows a wide QRS complex (namely, every other beat) 3–5,12 …”

Section: Discussionmentioning

confidence: 99%

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Right Bundle Branch Block on Alternate Beats during Acute Pulmonary Embolism

Shinde

Carbone

Shinde³

et al. 2011

Annals of Noninvasive Electrocardiology

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The electrocardiogram of a patient with acute pulmonary embolism showed right bundle branch block (RBBB) on alternate beats; following thrombolysis, the pattern evolved to persistent RBBB and eventually to normal conduction. Analysis of serial tracings suggested that the mechanism of RBBB alternans was tachycardia-dependent bidirectional bundle branch block, caused by prolongation of both anterograde and retrograde refractory periods (RPs) of the right bundle branch (RBB). The sinus impulse found the RBB refractory, and was conducted over the left bundle branch only, depolarizing the left ventricle and then attempting to penetrate retrogradely the RBB; at that time, however, the RBB was still refractory. When a QRS complex had a RBBB configuration, therefore, the RBB was not depolarized; the ensuing sinus impulse found the RBB fully responsive as a consequence of the long period intervening between two successive depolarizations, and resulted in normal intraventricular conduction. With right ventricular afterload decrease, the recovery of RBB anterograde and retrograde excitability was asynchronous, since the retrograde RP became normal earlier than the anterograde one. In accordance with the relatively short retrograde RP, the RBB was retrogradely invaded by the transseptal impulse coming from the left ventricle; this "shifted to the right" the anterograde RP of the RBB. The RBB, thus, was still refractory to the next sinus impulse, and RBBB again occurred; the RBB, thus, was once more depolarized retrogradely, and this led to perpetuation of RBBB. Finally, intraventricular conduction became normal owing to full normalization of RBB anterograde and retrograde refractoriness.

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Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Right Bundle Branch Block on Alternate Beats during Acute Pulmonary Embolism

Shinde

Carbone

Shinde³

et al. 2011

Annals of Noninvasive Electrocardiology

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show abstract

“…The 2:1 BBB pattern at 480‐msec CL may have two potential mechanisms: (1) tachycardia‐dependent (phase 3) alternans with bidirectional block; or (2) related to supernormal conduction in subjects with tachycardia‐dependent (phase 3) BBB 1,2 …”

Section: Commentarymentioning

confidence: 99%

“…In essence, the alternating anterograde and retrograde activation of the LBB causes an alternating left and right shift in the position of the supernormal phase, and this moving target can be hit only by every second impulse at a fixed CL, resulting in a 2:1 LBBB pattern. The occurrence of three successive beats with 1:1 LBBB pattern at the end of the third strip and the predominantly 4:3 LBBB pattern with occasional 2:1 LBBB pattern at even shorter CL (470‐450 msec) also might be explained by a supernormal conduction mechanism 1–3 …”

Section: Commentarymentioning

confidence: 99%