Objective—To assess signal-averaged electrocardiography
(SAECG) for evaluation of Boxers with arrhythmogenic
right ventricular cardiomyopathy (ARVC) and
identify dogs at risk for sudden death (SD) or death
related to congestive heart failure (CHF).
Animals—94 Boxers with ARVC and 49 clinically normal
Procedure—Boxers were screened for ARVC, and
severity was estimated by use of echocardiography,
24-hour ambulatory ECG, and SAECG. Statistical evaluation
was performed to identify significant differences
in SAECG variables relative to clinical outcome,
frequency of ventricular arrhythmias, and systolic
function. Sensitivity, specificity, and positive and negative
predictive values were evaluated for each
SAECG variable for occurrence of SD or death related
to CHF. Late potentials were also evaluated as a predictor
of cardiac-related death.
Results—Differences were detected in SAECG variables
on the basis of clinical outcome, systolic function,
and frequency of ventricular arrhythmias. More
severely affected dogs had significantly more abnormal
SAECG findings. The presence of late potentials,
defined as 2 abnormal root mean square values (of 4),
was associated with high sensitivity, specificity, and
negative predictive value for cardiac-related SD or
death secondary to CHF.
Conclusions and Clinical Relevance—Results suggest
that SAECG is a useful noninvasive diagnostic
test to evaluate dogs affected with ARVC and identify
individuals at risk for cardiac-related death. ( J Am Vet
Med Assoc 2004;225:1050–1055)
Objective—To assess heart rate variability (HRV) in
Boxers with arrhythmogenic right ventricular cardiomyopathy
(ARVC), assess the ability of HRV analysis
to identify differences in Boxers on the basis of
severity of their arrhythmia, and evaluate the use of
HRV to determine whether persistently high sympathetic
tone is present in these dogs.
Animals—24 Boxers with ARVC and 10 clinically normal
Procedure—Boxers were categorized as dogs with
congestive heart failure (CHF), dogs with ≤ 2 ventricular
premature complexes (VPCs)/24 h (designated
unaffected), or dogs with > 1,000 VPCs/24 h (designated
affected). Ambulatory electrocardiography (24
hours) was performed in each dog. Recordings were
analyzed for HRV variables at a commercial laboratory;
differences in HRV variables among groups were
compared with 1-way ANOVA.
Results—Compared with control non-Boxer dogs and
Boxers without CHF (affected and unaffected Boxers),
HRV was reduced in Boxers with CHF. No differences
in HRV variables were detected between affected and
unaffected Boxers. Inconsistent differences were
identified between the control dogs and Boxers without
CHF that had various degrees of arrhythmias.
Conclusions and Clinical Relevance—Results suggest
that persistently high sympathetic tone is not a
consistent feature of ARVC. Differences in some HRV
variables between Boxers without CHF and control
dogs suggest that Boxers may have different autonomic
control of heart rate, compared with that of
clinically normal non-Boxer dogs. The usefulness of
HRV analysis appears limited to Boxers with ARVC
that have systolic dysfunction and CHF. ( J Am Vet
Med Assoc 2004;224:534–537)
Objective—To evaluate spontaneous variability in the
frequency of ventricular arrhythmias and assess the
influence of day of ECG recording and day of week on
arrhythmia frequency in Boxers affected with arrhythmogenic
right ventricular cardiomyopathy (ARVC).
Animals—10 Boxers with ARVC with prior ambulatory
ECG recordings that included ≥ 500 ventricular premature
Procedure—Consecutive 24-hour ambulatory ECG
recordings were obtained during a 7-day period in
each dog. The number of ventricular premature complexes
and grade of the arrhythmia were obtained
from each recording. For each dog, the number of
ventricular premature complexes for each recording
was evaluated to identify any differences relative to
the day of recording (recording 1 to 7) and day of the
week (Monday through Sunday).
Results—Spontaneous variability accounted for as
much as 80% of the change in frequency of ventricular
premature complexes in dogs with frequent
arrhythmias; this value was almost 100% in dogs with
less frequent arrhythmias. Grade of arrhythmia was
less variable but was also inversely related to frequency
of arrhythmia. No significant differences in
frequency values were identified among days of
recording or among days of the week.
Conclusions and Clinical Relevance—Changes of
≤ 80% in the frequency of ventricular arrhythmias
may be within the limit of spontaneous variability in
dogs with ARVC. This degree of variability should be
considered in evaluations of ambulatory ECG recordings,
particularly in the assessment of the efficacy of
antiarrhythmic drugs. ( J Am Vet Med Assoc 2004;224:
Objective—To evaluate the use of in-hospital electrocardiography
(ECG) for detection of ventricular premature
complexes (VPC), compared with 24-hour
Animals—188 Boxers > 9 months old; 31 had a history
of syncope, and 157 were healthy (no history of
Procedure—In-hospital ECG was performed on all
Boxers for at least 2 minutes. Within 7 days after the
in-hospital ECG was completed, 24-hour ambulatory
ECG was performed.
Results—The specificity of in-hospital ECG was
100% for the detection of at least 50 VPC in a 24-hour
period in dogs with syncope and 93% in healthy dogs.
In-hospital ECG had poor sensitivity, although sensitivity
increased as the number of VPC per 24 hours
Conclusions and Clinical Relevance—Use of in-hospital
ECG is highly specific for detection of at least 50
VPC during a 24-hour period. However, in-hospital
ECG is insensitive, and a lack of VPC does not suggest
that the dog does not have a substantial number
of VPC during that same period. The use of in-hospital
ECG appears to be inadequate for screening purposes
and therapeutic evaluations in mature Boxers with
ventricular arrhythmic disease. (J Am Vet Med Assoc
Objective—To evaluate the use of 24-hour ambulatory
electrocardiography (AECG) for the detection of ventricular
premature complexes (VPC) in healthy dogs.
Animals—50 healthy mature dogs.
Procedure—A 24-hour AECG was performed on each
dog and evaluated for the presence of VPC.
Results—Fifty dogs weighing between 18.2 to 40.9 kg
(40 and 90 lb) representing 13 breeds were evaluated;
there were 4 sexually intact females, 21 spayed
females, 4 sexually intact males, and 21 castrated
males. Ages ranged from 1 to 12 years. Thirty-four dogs
had no VPC; 16 dogs had between 1 and 24 VPC. The
grade of arrhythmia ranged from 1 to 4, with 4 dogs
having an arrhythmia with a grade > 1. Significant differences
were not detected between the group of
dogs with VPC and those without VPC with regard to
sex, age, and minimum, maximum, or mean heart rate.
Conclusions and Clinical Relevance—We conclude
that healthy mature dogs have infrequent VPC, as
detected by use of 24-hour AECG. The presence of
numerous or sequential VPC may be suggestive of
cardiac or systemic disease and may indicate the
need for thorough clinical evaluation. (J Am Vet Med
Objective—To measure QT interval duration and QT
dispersion in Boxers and to determine whether QT
variables correlate with indices of disease severity in
Boxers with familial ventricular arrhythmias, including
the number of ventricular premature complexes per
day, arrhythmia grade, and fractional shortening.
Animals—25 Boxers were evaluated by ECG and
Procedure—The QT interval duration was measured
from 12-lead ECG and corrected for heart rate (QTc),
using Fridericia's formula. The QT and QTc were calculated
for each lead, from which QT and QTc dispersion
were determined. Echocardiography and 24-hour
ambulatory ECG were performed to evaluate for
familial ventricular arrhythmias. Total number of ventricular
premature complexes, arrhythmia grade, and
fractional shortening were determined and used as
indices of disease severity.
Results—There was no correlation between any QT
variable and total number of ventricular premature
complexes, arrhythmia grade, or fractional shortening.
No difference between QT dispersion and QTc
dispersion was identified, and correction for heart rate
did not affect the results.
Conclusions and Clinical Relevance—QT interval
duration and dispersion did not correlate with indices
of disease severity for familial ventricular arrhythmias.
Heart rate correction of the QT interval did not appear
to be necessary for QT dispersion calculation in this
group of dogs. QT dispersion does not appear to be a
useful noninvasive diagnostic tool in the evaluation of
familial ventricular arrhythmias of Boxers.
Identification of affected individuals at risk for sudden
death remains a challenge in the management of this
disease. (Am J Vet Res 2001;62:1481–1485)
Objective—To evaluate the coding region of the cardiac
actin gene in Doberman Pinschers with dilated
cardiomyopathy (DCM) for mutations that could be
responsible for the development of the condition
Animals—28 dogs (16 Doberman Pinschers with
DCM and 12 mixed-breed control dogs).
Procedure—Ten milliliters of blood was collected
from each dog for DNA extraction.
Polymerase chain reaction (PCR) primers were
designed to amplify canine exonic regions, using the
sequences of exons 2 to 6 of the cardiac actin gene.
Single-stranded conformational polymorphism analysis
was performed for each exon with all samples.
Autoradiographs were analyzed for banding patterns
specific to affected dogs. The DNA sequencing was
performed on a selected group of affected and control
Results—Molecular analysis of exons 2 to 6 of the
cardiac actin gene did not reveal any differences in
base pairs between affected dogs and control dogs
selected for DNA evaluation.
Conclusions—Mutations in exons 5 and 6 of the cardiac
actin gene that have been reported in humans
with familial DCM do not appear to be the cause of
familial DCM in Doberman Pinschers. Additionally,
evaluation of exons 2 to 6 for causative mutations did
not reveal a cause for inherited DCM in these
Doberman Pinschers. Although there is evidence that
DCM in Doberman Pinschers is an inherited problem,
a molecular basis for this condition remains unresolved.
Evaluation of other genes coding for
cytoskeletal proteins is warranted. ( Am J Vet Res
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)
Case Description—A 12-week-old female English Springer Spaniel was evaluated for lethargy, vomiting, and pyrexia 1 week after treatment of patent ductus arteriosus (PDA) via coil occlusion.
Clinical Findings—Test results were consistent with septicemia, and the assumption was made that the PDA occlusion coils were infected. Radiography revealed partial migration of the coil mass into the pulmonary artery and signs of congestive heart failure.
Treatment and Outcome—After successful treatment of the septicemia and heart failure, surgical removal of the coils and resection of the PDA were undertaken. Although the coil that embolized to the pulmonary vasculature was left in place, the dog's clinical signs resolved.
Clinical Relevance—This case highlights the fact that as PDA coil occlusion devices become more widely used in dogs, practitioners must be prepared to treat implant infections aggressively, with both medical and surgical interventions if necessary.
Objective—To determine the prevalence of ventricular arrhythmias in clinically normal adult Boxers.
Design—Prospective cross-sectional study.
Animals—301 Boxers (181 females and 120 males) > 1 year old with echocardiographically normal systolic function and no history of syncope or congestive heart failure.
Procedures—Physical examination, which included echocardiography, was performed on all dogs. A 24-hour ambulatory ECG was performed on each dog, and results were evaluated to assess ventricular arrhythmias. Statistical evaluation was performed to determine correlations between the total number of ventricular premature complexes (VPCs)/24 h, grade of ventricular arrhythmia, and age of the dogs.
Results—Age of dogs ranged from 1 to 16 years (median, 4 years). Number of VPCs/24 h in each dog ranged from 0 to 62,622 (median, 6 VPCs/24 h). Grade of arrhythmias ranged from 0 to 3 (median, 1). Age was correlated significantly with number of VPCs/24 h (r = 0.43) and with grade of arrhythmia (r = 0.37). Number of VPCs/24 h was significantly correlated with grade of arrhythmia (r = 0.82).
Conclusions and Clinical Relevance—Clinically normal adult Boxers generally had < 91 VPCs/24 h and an arrhythmia grade < 2. Boxers with > 91 VPCs/24 h were uncommon and may have represented dogs with arrhythmogenic right ventricular cardiomyopathy or other disease processes that could have resulted in the development of ventricular arrhythmias.