Frequency distribution, variance, and moving average of left ventricular rhythm and contractility during atrial fibrillation in dog.
Mean levels of left ventricular rhythm and contractility averaged over arrhythmic beats would characterize the average cardiac performance during atrial fibrillation (AF). However, no consensus exists on the minimal number of beats for their reliable mean values. We analyzed their basic statistics to find out such a minimal beat number in canine hearts. We produced AF by electrically stimulating the atrium and measured left ventricular arrhythmic beat interval (RR) and peak isovolumic pressure (LVP). From these, we calculated instantaneous heart rate (HR = 60,000/RR), contractility (E(max) = LVP/isovolumic volume above unstressed volume), and beat interval ratio (RR1/RR2). We found that all their frequency distributions during AF were variably nonnormal with skewness and kurtosis. Their means +/- standard deviations alone cannot represent their nonnormal distributions. A 90% reduction of variances of E(max) and RR1/RR2 required a moving average of 15 and 24, respectively, arrhythmic beats on the average, whereas that of RR and HR required 60 beats on the average. These results indicate that a statistical characterization of arrhythmic cardiodynamic variables facilitates better understanding of cardiac performance during AF.
Morita
Terumasa
T
Department of Cardiovascular Physiology, Okayama University Graduate School of Medicine and Dentistry, Okayama, 700-8558 Japan.
Araki
Junichi
J
Oshima
Yu
Y
Mitani
Hidenobu
H
Iribe
Gentaro
G
Mohri
Satoshi
S
Shimizu
Juichiro
J
Sano
Shunji
S
Kajiya
Fumihiko
F
Suga
Hiroyuki
H
D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology*; D004285:Dogs; D006339:Heart Rate; D009200:Myocardial Contraction; D011312:Pressure; D016277:Ventricular Function, Left