Procedure—The HRV was analyzed in time- and frequency-
domains from 24-hour ambulatory electrocardiographic
(Holter) monitor recordings. Activity during
paired tests (tests 1 and 2) was similar (17 dogs) or
nearly identical (7). Holter recordings and HRV analyses
of those 17 dogs were repeated at a mean ± SD
of 65 ± 50 weeks (median, 51 weeks; range, 10 to
177 weeks), whereas it was repeated for the other 7
dogs at 3 to 9 weeks (mean, 7.3 ± 2.1 weeks).
Results—Differences between test 1 and test 2
were not significantly different, except for 24-hour
means of the normal beat-to-normal beat (NN) intervals
in all 5-minute segments. Strongest correlations
were for SD of all NN intervals and root mean square
successive difference between adjacent NN intervals
of the time-domain analyses and total power, verylow
frequency power, and high-frequency power of
the frequency-domain analyses. When activity during
tests 1 and 2 in 7 dogs was stringently controlled,
the differences were not significantly different, and
correlation factors for the 24-hour HRV analyses
Conclusion and Clinical Relevance—Variables
from sequential HRV analyses in overtly healthy
Doberman Pinschers with normal echocardiograms
are moderately stable when physical activity is not
stringently controlled and extremely stable for at least
3 to 9 weeks when physical activity is stringently controlled.
(Am J Vet Res 2002;63:53–59)
Procedure—24-hour ambulatory electrocardiographic
(Holter) recordings with > 90% scan quality obtained
the same day that echocardiography was performed
Results—Holter recordings from 42 of 44 (95%) dogs
contained ventricular premature complexes (VPC).
Fifteen of 44 (34%) dogs had > 100 VPC, 9 (20%) had
> 500 VPC, and 5 (11%) had > 1,000 VPC.
Nonsustained (< 30 seconds) ventricular tachycardia
was detected in 4 dogs. Eighteen of 27 (67%) dogs
with > 100 VPC, any couplets or triplets of VPC, or
ventricular tachycardia developed dilated cardiomyopathy
within 1 year, compared with 8 of 17 (47%)
dogs with < 100 VPC, no couplets or triplets of VPC,
and no ventricular tachycardia. Of the 18 dogs that did
not develop dilated cardiomyopathy within 1 year, 11
(61%) did so within 3 years.
Conclusions and Clinical Relevance—Results suggest
that a high percentage of Doberman Pinschers
with equivocal echocardiographic evidence of dilated
cardiomyopathy will be found to have VPC during 24-hour ambulatory electrocardiography and that most
will develop echocardiographic abnormalities indicative
of cardiomyopathy. (J Am Vet Med Assoc
Objective—To determine whether heart rate variability
(HRV) is reduced in Doberman Pinschers with dilated
Animals—62 overtly healthy Doberman Pinschers.
Procedure—Heart rate variability was analyzed in time
and frequency domains from data obtained during 24-hour ambulatory electrocardiographic Holter recordings in 41 overtly healthy Doberman Pinschers with
normal echocardiograms and 21 overtly healthy
Doberman Pinschers with abnormal echocardiograms.
Results—Heart rate variability usually was greater
during night versus day, and 2 dogs with the most
severe myocardial failure had reduced HRV.
Conclusions and Clinical Relevance—Reduced HRV
was detected only in Doberman Pinschers with the
most severe myocardial failure. Thus, HRV in less
severely affected dogs is not reduced, or the normal
sinus arrhythmia of dogs renders HRV relatively insensitive.
Analysis of HRV did not provide additional information
relative to the severity of left ventricular dysfunction
or risk of sudden death from that which could
be derived from echocardiography, analysis of Holter
recordings, and signal-averaged electrocardiography.
(J Am Vet Med Assoc 2001;219:1076–1080)
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
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)
Objective—To characterize the salient variables of
the time-domain analysis of heart rate variability
(HRV) in clinically normal Doberman Pinschers and to
compare those variables with those of Doberman
Pinschers with cardiomyopathy and mild to moderate
Animals—46 Doberman Pinschers.
Procedure—HRV was analyzed in the time-domain
from 24-hour Holter recordings obtained from 28
Doberman Pinschers with normal echocardiograms
and 18 Doberman Pinschers with echocardiograms
consistent with mild to moderate myocardial failure.
Results—Significant differences in HRV variables
between the 2 groups of dogs were not detected.
The HRV was greater during the nighttime (12 AM to
6 AM), compared with the 24-hour day and an 18-hour
(6 AM to 12 AM) period.
Conclusions and Clinical Relevance—HRV of dogs
with mild to moderate myocardial failure was not different
from that of clinically normal dogs, because
there were no disturbances of autonomic balance,
baroreceptor function, and other factors that influence
HRV in the dogs with cardiomyopathy, or the
sensitivity of time-domain analysis was overwhelmed
by normal sinus arrhythmia. The techniques now
used to study HRV have important limitations, especially
in dogs, and better noninvasive tests of autonomic
function are needed. ( Am J Vet Res 2000;61:
Objective—To identify, by means of 24-hour ambulatory
electrocardiography, electrocardiographic abnormalities
in overtly healthy Doberman Pinschers in
which results of echocardiography were abnormal.
Design—Clinical case series.
Animals—56 (35 male, 21 female) overtly healthy
Doberman Pinschers with echocardiographic evidence
of cardiomyopathy on initial examination that
subsequently died of cardiomyopathy.
Procedure—Twenty-four-hour ambulatory electrocardiographic
(Holter) recordings obtained at the time of
initial examination were reviewed. For all dogs, scan
quality was > 90%.
Results—Initial Holter recordings of all 56 dogs contained
ventricular premature contractions (VPC).
Thirty-six (65%) dogs had > 1,000 VPC/24 h, 17 (31%)
had > 5,000 VPC/24 h, and 11 (19%) had > 10,000
VPC/24 h. Fifty-four (96%) dogs had couplets of VPC,
37 (66%) had triplets of VPC, and 36 (64%) had
episodes of nonsustained (< 30 seconds) ventricular
tachycardia. Number of VPC/24 h during the initial
Holter recordings was positively correlated with numbers
of couplets and triplets of VPC and number of
ventricular escape beats and negatively correlated
with left ventricular fractional shortening. Twentyeight
dogs died suddenly prior to the putative onset
of congestive heart failure.
Conclusions and Clinical Relevance—Results suggested
that along with echocardiography, 24-hour
ambulatory electrocardiography can be used to help
identify overtly healthy Doberman Pinschers with
cardiomyopathy. (J Am Vet Med Assoc 2000;217:
Objective—To determine electrocardiographic parameters
in healthy llamas and alpacas.
Animals—23 llamas and 12 alpacas.
Procedure—Electrocardiography was performed in
nonsedated standing llamas and alpacas by use of multiple
simultaneous lead recording (bipolar limb, unipolar
augmented limb, and unipolar precordial leads).
Results—Common features of ECGs of llamas and
alpacas included low voltage of QRS complexes, variable
morphology of QRS complexes among camelids,
and mean depolarization vectors (mean electrical
axes) that were directed dorsocranially and to the
right. Durations of the QT interval and ST segment
were negatively correlated with heart rate.
Conclusions and Clinical Relevance—ECGs of
acceptable quality can be consistently recorded in
nonsedated standing llamas and alpacas. Features of
ECGs in llamas and alpacas are similar to those of other
ruminants. Changes in the morphology of the QRS
complexes and mean electrical axis are unlikely to be
sensitive indicators of ventricular enlargement in llamas
and alpacas. (Am J Vet Res 2004;65:1719–1723)