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Characteristics of accessory pathways exhibiting decremental conduction
C J Murdock1, J W Leitch, W S Teo
1Cardiac Investigation Unit, University Hospital, University of Western Ontario, London, Canada.
Insights
Decremental conduction over accessory pathways is uncommon, affecting 7.6% of patients. Anterograde decremental conduction typically involves right-sided or septal pathways, often lacking retrograde function.
Area of Science:
- Cardiology
- Electrophysiology
Background:
- Accessory pathways are a common cause of supraventricular tachycardia.
- Decremental conduction is a property of some accessory pathways, influencing their electrophysiologic behavior.
Purpose of the Study:
- To investigate the prevalence, electrophysiologic characteristics, and functional significance of decremental conduction in accessory pathways.
- To determine the anatomical locations associated with decremental conduction.
Main Methods:
- Retrospective analysis of 653 patients with accessory pathways identified during electrophysiologic study.
- Examination of decremental conduction properties in both anterograde and retrograde directions.
Main Results:
- Decremental conduction was identified in 7.6% of patients (50/653).
- Anterograde decremental conduction was predominantly associated with right-sided or septal pathways (14/15).
- Patients with anterograde decremental conduction had longer shortest RR intervals during atrial fibrillation compared to controls.
Conclusions:
- Decremental conduction over accessory pathways is an uncommon finding.
- Anterograde decremental conduction is typically associated with right-sided or septal accessory pathways that may not conduct retrogradely.
Abstract:
The prevalence, electrophysiologic characteristics and functional significance of decremental conduction over an accessory pathway were examined in this retrospective study of 653 patients who had an accessory pathway demonstrated at electrophysiologic study. Decremental conduction was identified in 50 patients (7.6%). In 15 patients with anterograde decremental conduction, the accessory pathway was right parietal or septal in 14 patients and left parietal in 1 patient. In the 40 patients with retrograde decrement, the accessory pathway was left parietal in 19, posteroseptal in 13, right parietal in 2 and right anteroseptal in 6 patients. Anterograde conduction over the accessory pathway was absent in 11 of the 40 patients with retrograde decrement. Retrograde conduction over the accessory pathway was absent in 9 patients with anterograde decrement. There was no significant difference in the accessory pathway effective refractory period, or shortest cycle length with 1:1 conduction over the accessory pathway in anterograde and retrograde directions. The shortest RR interval in atrial fibrillation between 2 preexcited QRS complexes was longer in patients with anterograde decremental conduction than in a control group of patients with anterograde-conducting accessory pathways without decremental properties. These data demonstrate that decremental conduction over accessory pathways is uncommon. Anterograde decremental conduction usually occurs in right-sided or septal pathways that often do not conduct in the retrograde direction.