AJP - Heart and Circulatory Physiology, Vol 267, Issue 4 1254-H1262, Copyright © 1994 by American Physiological Society
Contraction-excitation feedback in atrial reentry: role of velocity of mechanical stretch
T. Yamashita, N. Oikawa, Y. Murakawa, T. Nakajima, M. Omata and H. Inoue
Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
To determine the effects of atrial stretch on atrial flutter, we analyzed
variations in atrial flutter cycle length (CL) caused by ventricular
contraction in five dogs with artificially induced atrioventricular block.
In contrast to absence of variations in CL during sustained ventricular
asystole, atrial stretch by ventricular contraction consistently produced
phasic variations in CL. The variations were not confined to any specific
atrial sites, but depended on the time of ventricular contraction relative
to atrial activation phase. The phase-response curve of the variations was
closely related to that of the velocity of changes in the atrial pressure
with no time lags, but not to that of the atrial pressure itself.
Pharmacological denervation did not abolish the variations. Conventional
electrophysiological study revealed greater changes in intra-atrial
activation time by atrial stretch at a short pacing cycle length than at a
longer one, suggestive of changes in repolarization by mechanical stretch.
In conclusion, atrial stretch caused by ventricular contraction produces
phasic variations in CL, the extent of which depends on the velocity of the
mechanical stretch of atrial muscles.
