Key result
Transseptal conduction time normally measures ~0.06 seconds but prolongs under pathologic conditions.
Why the study?
The transseptal conduction time in the human heart and its variation under pathologic conditions were not well characterized.
Case Report (n=4)
Estimates from animal data should not guide practice; leaves open human validation of transseptal conduction times.
Four unusual cases of bundle-branch block with a parasystolic rhythm originating in the blocked ventricle are described. Varying interference of natural and parasystolic impulses permits calculation of the transseptal conduction time in man by two independent methods. The physiologic basis of each method is discussed and its validity confirmed by application to data from animal experiments available in the literature. The normal transseptal conduction time in the human heart is estimated to be 0.06 to 0.07 second in both directions. This is about twice as long as in the dog. Under pathologic conditions, it may lengthen to at least 0.115 second. A functionally "complete" bundle-branch block can result from a delay in impulse transmission down one of the bundle branches greater than the transseptal conduction time, and need not be due to total anatomic interruption of one bundle branch.
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Katz et al. (1963) conducted a case report in Bundle-branch block with a parasystolic rhythm (n=4). Natural and parasystolic impulses was evaluated on Transseptal conduction time. The normal transseptal conduction time in the human heart is estimated to be 0.06 to 0.07 second in both directions, which may lengthen to at least 0.115 second under pathologic conditions.