The Transseptal Conduction Time in the Human Heart

Abstract

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.