Severity in myocardial dysfunction contributed to long-term fluctuation of heart rate, rather than short-term fluctuations.
BACKGROUND
It is known that heart rate shows complex behavior, long-term fluctuation of heart rate, and short-term fluctuations in heart failure. Analyzing these properties and examining the relationship to the disease, severity may increase the understanding of the background of heart rate variability (HRV).


METHODS
In 61 patients (mean age 65 +/- 9 years, 32 ischemic heart disease, 29 cardiomyopathy), with myocardial dysfunction, 24-hour ambulatory electrocardiography was performed. After the construction of the time series of R-R intervals, 15 HRV parameters were measured, including mean heart rate, standard deviation of N-N intervals (SDNN), ratio of low frequency/high frequency power (LF/HF), HRV triangular index (TI), and ratio of length/width at the 90% level of all scattered points.


RESULTS
By using the multiple regression analysis, we tested which HRV parameter (HR, SDNN, LF/HF, TI, or length/width) independently correlated with left ventricular ejection fraction (EF) or left ventricular diastolic dimension (EDD). The results demonstrated that TI and SDNN independently correlated with EF (multiple R = 0.59). Moreover, TI and SDNN independently correlated with EDD (multiple R = 0.45).


CONCLUSIONS
TI and SDNN were indicators of the disease severity in myocardial dysfunction, while LF/HF, indicators of autonomic tone, did not have such an ability. It was of interest that the disease severity contributed to long-term fluctuations (TI, SDNN) of heart rate, rather than short-term fluctuations (LF/HF).
Minamihaba
Osamu
O
First Department of Internal Medicine, Yamagata University School of Medicine, Yamagata, Japan.
Yamaki
Michiyasu
M
Tomoike
Hitonobu
H
Kubota
Isao
I
D000368:Aged; D002311:Cardiomyopathy, Dilated / Q000503:physiopathology*; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000503:physiopathology*; D012044:Regression Analysis; D012815:Signal Processing, Computer-Assisted; D016277:Ventricular Function, Left