Atrial echo beats resulting from a reciprocating mechanism involving the bundle branches were produced by premature atrial impulses in a patient with an A V nodal bypass tract. The mechanism of the arrhythmia was suggested by the presence of a retrograde His bundle deflection which appeared 'sandwiched' in between a QRS complex with complete right bundle branch morphology and a negative P wave. Though at a shorter cycle length the His bundle was still activated retrogradely echo beats were not seen because the retrograde H deflection occurred too early, when both bypass tract and A V node were still effectively refractory. At the faster driven rate concealed retrograde activation of the right branch (by the premature impulse) was responsible for the right bundle branch block patterns shown by the post premature driven beat.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine