Jan 31, 2006

Concealed conduction in nodal dual pathways: depressed conduction, prolonged refractoriness, or reset excitability cycle?

Heart Rhythm : the Official Journal of the Heart Rhythm Society
Bochun XuMichel Lavallée

Abstract

Concealed conduction is recognized as a major determinant of atrioventricular (AV) nodal filtering properties, but little is known about the underlying mechanisms. The purpose of this study was to consistently elicit concealed conduction through the AV node and to determine the involvement of slow and fast pathways in resultant changes in nodal function. The concealment zone (nodal effective refractory period minus nodal functional refractory period of atrium) was determined in six rabbit heart preparations with and without a conditioning cycle (10 ms longer than nodal effective refractory period). Nodal function curves were constructed for concealed cycle lengths selected within the concealment zone. Experiments were repeated after slow pathway ablation. When assessed with a blocked beat alone, a narrow concealment zone (22 +/- 12 ms, n = 3) was observed in 50% of the preparations. In contrast, when assessed with a blocked beat preceded by a conducted conditioning beat, a wider concealment zone (77 +/- 47 ms, n = 6, P <.03) was observed in all preparations. Increases in the concealed cycle length resulted in graded increases in the nodal effective refractory period and nodal functional refractory period and graded rightward sh...Continue Reading

Mentioned in this Paper

Biochemical Pathway
Depressed - Symptom
Action Potentials
Refractory Period, Electrophysiological
Etiology
Atrial Fibrillation
Chinchilla Rabbits
Refractory Period
Cardiac Conduction System
Structure of Atrioventricular Node

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