Aug 1, 2006

Unified rate-dependent atrioventricular nodal function: consistent recovery and fatigue properties revealed with S1S2S3 protocols and different recovery indexes

Heart Rhythm : the Official Journal of the Heart Rhythm Society
Rafik TadrosJ Billette


Rate-dependent nodal properties are commonly assessed with premature protocols performed at different basic rates. Because characteristics of responses differ with recovery time index, the true nature of nodal rate-dependent properties is elusive. The purpose of this study was to reveal consistent nodal rate-dependent properties regardless of selected recovery index. With S(1)S(2)S(3) protocols, we independently varied basic and pretest cycle lengths and thereby distinguished cumulative from noncumulative effects of rate on nodal conduction time in rabbit heart preparations. Nodal responses to 30 basic and pretest cycle length combinations (five with identical basic and pretest cycles as in standard protocols) were analyzed using both atrial (AA) and His-atrial (HA) intervals as recovery index. AA and HA curves had an identical shape for any of 30 steady-state conditions. When assessed with constant pretest cycle lengths, cumulative effects (fatigue) of shortened basic cycle lengths were also independent of recovery index. Shortening of pretest cycle length at fixed basic rates led to apparent inhibitory and facilitatory effects when assessed with AA and HA curves, respectively. These effects vanished when a single long cycle w...Continue Reading

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Mentioned in this Paper

Neuro-Oncological Ventral Antigen 2
Left Bundle Branch of His
Chinchilla Rabbits
Atrial Function
Structure of Atrioventricular Node
Entire Crista Terminalis Cordis
NODAL gene
Entire Atrium

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