Temporal patterns of progression and regression of electrical and mechanical remodeling of the atrium.
OBJECTIVE
We evaluated serial changes of electrical and mechanical parameters of atrial remodeling in dogs subjected to rapid atrial pacing.


BACKGROUND
Prolonged rapid atrial excitation causes electrical and mechanical remodeling, which contributes to persistence of atrial fibrillation and clot formation. However, the temporal relationship between these two types of atrial remodeling remains unknown.


METHODS
In 8 dogs, rapid pacing at 400 ppm was continued for 14 days. The electrophysiologic and transesophageal echocardiographic studies were performed on the day before and after 2, 7, and 14 days of rapid pacing, then 1 and 7 days after the cessation of pacing. These were compared with sham-operated dogs (instrumented but not paced, n=6).


RESULTS
With rapid pacing, there was an immediate shortening of the effective refractory period (ERP) and decreases in the transmitral atrial wave velocity (MAV) and the left atrial appendage emptying velocity (LAAV). In contrast, conduction velocity (CV) decreased and the left atrial appendage area (LAAA) increased progressively over 14 days. During the recovery, ERP, MAV, and LAAV returned to the baseline in 1 day, whereas CV and LAAA did in 7 days. ERP was highly positively correlated with LAAV (r=0.78, p<0.001) and MAV (r=0.73, p<0.001), while CV was negatively correlated only with LAAA (r=-0.58, p<0.001).


CONCLUSIONS
Pacing-induced electrical and mechanical remodeling of the atrium exhibits divergent patterns of progression and regression such that changes of ERP and contractile function take place more rapidly than those of CV and atrial size.
Kinebuchi
Osamu
O
Cardiology Division, Department of Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, 160-8582 Tokyo, Japan.
Mitamura
Hideo
H
Shiroshita-Takeshita
Akiko
A
Kurita
Yasuo
Y
Ohashi
Narutaka
N
Tanimoto
Kojiro
K
Fukuda
Yukiko
Y
Ieda
Masaki
M
Sato
Toshiaki
T
Hara
Motoki
M
Takatsuki
Seiji
S
Ogawa
Satoshi
S
D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology*; D016275:Atrial Function; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002304:Cardiac Pacing, Artificial; D004195:Disease Models, Animal; D018450:Disease Progression; D004285:Dogs; D018618:Echocardiography, Doppler, Color; D017548:Echocardiography, Transesophageal; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006325:Heart Atria / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology; D008297:Male; D008955:Models, Cardiovascular; D012032:Refractory Period, Electrophysiological