Electrocardiogram of the month. Rosenbaum's syndrome
Johnson, C.D.
Boletin de la Asociacion Medica de Puerto Rico 92(1-3): 55-57
2000
ISSN/ISBN: 0004-4849 PMID: 10846289 Document Number: 6687
This involves simultaneous conduction impairment/block in the three main terminal fascicles (disregarding the middle septal fascicle), the right bundle branch and the two (both) divisions of the left bundle branch. This pattern has been regarded by some authors as bilateral bundle branch block. But other ECG authorities reserve the terco "Bilateral Bundle Branch Block" for the presence of involvement, complete third degree block, of both the main bundle branches, presenting alternating or intermittent RBBB and left bundle branch block (LBBB) with a changing, different P-R interval. These hold that this is the only absolute evidence that both bundle branches are involved. Bifascicular block is reflected by a combination of RBBB with LAH, or RBBB with LPH. RBBB with either hemiblock, plus a first degree AV block (prolonged P-R interval) or a second degree AV block (dropped beats) has been suggested to be a manifestation of TB. However, the third site of block may not necessarily be in the remaining incompletely blocked division, but at the level of the AV node or Bundle of His. A His Bundle recording would be necessary to distinguish this third site of partial block. TB patterns are usually associated with Mobitz type II AV block. Complete block in all three fascicles at the same time would lead to complete AV block. A change in heart rate may bring about a change in the degree of block, i.e. rate-dependency TB. A few milliseconds difference may determine whether an impulse is normally conducted, entirely blocked or show concealed conduction.
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