Apr 1, 1988

Selective functional characteristics of rate-induced fatigue in rabbit atrioventricular node

Circulation Research
J BilletteM St-Vincent


The slowly developing rate-induced prolongation in atrioventricular nodal conduction time, termed "fatigue," was selectively studied using specifically designed stimulation protocols in isolated rabbit heart preparations. A nodal recovery curve (A2H2 versus H1A2 intervals; nodal conduction time of each premature beat plotted against corresponding recovery time) was obtained before and after a stable and nearly maximum fatigue had been reached by driving the atrium for 5 minutes at a fast rate close to the upper limit of 1:1 nodal conduction. The fatigue uniformly prolonged all A2H2 intervals (12.3 +/- 1.3 msec) and systematically increased the minimum H1A2 interval at which complete nodal block occurred (24.8 +/- 4.0 msec) (p less than 0.01, n = 6). To study the rate and time dependence of fatigue, nodal conduction times were obtained during three rapid 5-minute pacings corresponding to 50%, 75%, and 100% shortening of the pacing interval in the 1:1 nodal conduction range. The respective maximum fatigue-induced increases in conduction time were 5.4 +/- 1.8, 9.0 +/- 2.7, and 12.5 +/- 2.1 msec (p less than 0.01, n = 6). However, the pacing interval had no significant effect on the time required to reach either 50% (17.1 +/- 3.5 s...Continue Reading

Mentioned in this Paper

Right Atrial Structure
Nerve Conduction Function
Chinchilla Rabbits
Cardiac Conduction System
Structure of Atrioventricular Node
NODAL gene
Entire Atrium
Entire Atrioventricular Node
Heart Atrium

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