Abstract
Objective—To determine correlations between timedomain and frequency-domain variables of heart rate variability (HRV) derived from 24-hour recordings obtained by use of an ambulatory electrocardiographic recorder (Holter monitor).
Animals—59 overtly healthy Doberman Pinschers (41 without echocardiographic evidence of cardiomyopathy and 18 with precongestive heart failure attributable to cardiomyopathy).
Procedure—The HRV was analyzed from 24-hour recordings. Variables were calculated from the entire 24-hour recording as well as 4 user-selected time epochs. Comparisons were made for total power to SD of normal beat-to-normal-beat (NN) intervals (SDNN), ultra-low frequency power to SD of the means of NN intervals, low-frequency power and verylow- frequency power to mean of the SD of NN intervals, and high-frequency (HF) power to the root mean square successive difference of NN intervals (RMSSD) and percentage of NN intervals that varied from the previous NN interval by > 50 milliseconds (PNN50).
Results—58 of 66 (88%) comparisons revealed significant values, indicating that relationships between variables were not random (r > 0.7 in 41 of 66 [62%]) comparisons). Strong correlations (r > 0.8) were found between the square root of total power and SDNN and between HF power and RMSSD.
Conclusions and Clinical Relevance—Time-domain surrogates for variables of frequency-domain analysis variables that correlated in the dogs reported here are the same ones that reportedly correlate in humans. When 24-hour recordings obtained by use of a Holter monitor are used to calculate HRV, SDNN and total power as well as RMSSD and HF power are interchangeable. (Am J Vet Res 2001;62:1787–1792)