Abstract
Depressed heart rate variability (HRV) is associated with increased mortality and
morbidity with various forms of heart disease, and the Duke treadmill score (DTS)
provides diagnostic and prognostic information for the evaluation of patients with
coronary artery disease (CAD). Our study was aimed at assessing any possible correlation
between HRV and DTS in stable CAD. We evaluated the correlation between the HRV assessed
by using 24 hour ambulatory ECG monitoring, and treadmill exercise score in 37 patients
with angiographically proven and clinically stable CAD. In univariate analysis, DTS
showed a significant negative correlation with age (r = −0.89, p < 0.01) and a significant
positive correlation with the square root of the mean of the sum of the squares of
differences between adjacent R-R intervals (RMSSD) (r = 0.67, P < 0.05), percent difference
between adjacent normal R-R intervals >50 ms (PNN50) (r = 0.69, P < 0.05), and mean
of the standard deviation of all R-R intervals in all the 5-minute intervals (HRVM)
(r = 0.63, P < 0.05). There is no significant correlation between DTS and standard
deviation of all R-R intervals (SDNN), standard deviation of the averages of R-R intervals
in all 5-minute segments of the entire recordings (SDANN) and standard deviation of
the SDNN in all the 5-minute intervals (HRVSD). In multiple regression analysis, age
was the only independent significant predictor of DTS (p < 0.01). DTS decreased with
advancing age. SDNN, SDANN, RMSSD, HRVM and HRVSD were not apparent predictors for
detecting of DTS. Age was an independent predictor of DTS. Although DTS was correlated
with RMSSD, PNN50 and HRVM in patients with stable CAD, time domain parameters of
HRV were not appearent predictor for DTS.
