| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Department of Cell Biology and Physiology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
The mechanisms responsible for atrioventricular
(AV) delay remain unclear, in part due to the inability to map
electrical activity by conventional microelectrode techniques. In this
study, voltage-sensitive dyes and imaging techniques were refined to detect action potentials (APs) from the small cells comprising the AV
node and to map activation from the "compact" node. Optical APs
(124) were recorded from 5 × 5 mm (~0.5-mm depth) AV zones of
perfused rabbit hearts stained with a voltage-sensitive dye. Signals
from the node exhibited a set of three spikes; the first and third
(peaks I and
III) were coincident with atrial (A)
and ventricular (V) electrograms, respectively. The second spike
(peak II) represented the firing of
midnodal (N) and/or lower nodal (NH) cell APs as indicated by
their small amplitude, propagation pattern, location determined from
superimposition of activation maps and histological sections of the
node region, dependence on depth of focus, and insensitivity to
tetrodotoxin (TTX). AV delays consisted of
1 (49.5 ± 6.59 ms, 300-ms
cycle length), the interval between peaks
I and II (perhaps AN
to N cells), and 2 (57.57 ± 5.15 ms), the interval between peaks
II and III (N to V
cells). The conductance time across the node was 10.33 ± 3.21 ms,
indicating an apparent conduction velocity
(
N) of 0.162 ± 0.02 m/s
(n = 9) that was insensitive to TTX.
In contrast, 1 correlated with
changes in AV node delays (measured with surface electrodes) caused by
changes in heart rate or perfusion with acetylcholine. The data provide
the first maps of activation across the AV node and demonstrate that
N is faster than previously presumed. These findings are inconsistent with theories of decremental conduction and prove the existence of a conduction barrier between the
atrium and the AV node that is an important determinant of AV node
delay.
rabbit atrioventricular node; compact node; atrioventricular nodal
delay; decremental conduction; atrioventricular node conduction; photodiode array; voltage-sensitive dyes; 4-[
-[2-(di-n-butylamino)-6-naphthyl]vinyl]pyridinium
This article has been cited by other articles:
|
|
 |
|
  D. K. Racker The AV junction region of the heart: a comprehensive study correlating gross anatomy and direct three-dimensional analysis. Part II. Morphology and cytoarchitecture Am J Physiol Heart Circ Physiol, May 1, 2004; 286(5): H1853 - H1871. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Restivo, D. O. Kozhevnikov, and M. Boutjdir Optical mapping of activation patterns in an animal model of congenital heart block Am J Physiol Heart Circ Physiol, April 1, 2001; 280(4): H1889 - H1895. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. R. Efimov; and B.-R. Choi Letters to the Editor Am J Physiol Heart Circ Physiol, November 1, 1998; 275(5): H1905 - H1909. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Wu, J. Wu, J. Olgin, J. M. Miller, and D. P. Zipes Mechanisms Underlying the Reentrant Circuit of Atrioventricular Nodal Reentrant Tachycardia in Isolated Canine Atrioventricular Nodal Preparation Using Optical Mapping Circ. Res., June 8, 2001; 88(11): 1189 - 1195. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
