Objective—To evaluate the effect of 4 antiarrhythmic
treatment protocols on number of ventricular premature
complexes (VPC), severity of arrhythmia, heart
rate (HR), and number of syncopal episodes in Boxers
with ventricular tachyarrhythmias.
Design—Randomized controlled clinical trial.
Procedure—Dogs with > 500 VPC/24 h via 24-hour
ambulatory ECG (AECG) were treated with atenolol
(n = 11), procainamide (11), sotalol (16), or mexiletine
and atenolol (11) for 21 to 28 days. Results of pre- and
posttreatment AECG were compared with regard to
number of VPC/24 h; maximum, mean, and minimum
HR; severity of arrhythmia; and occurrence of syncope.
Results—Significant differences between pre- and
posttreatment number of VPC, severity of arrhythmia,
HR variables, or occurrence of syncope were not
observed in dogs treated with atenolol or procainamide.
Significant reductions in number of VPC,
severity of arrythmia, and maximum and mean HR
were observed in dogs treated with mexiletineatenolol
or sotalol; occurrence of syncope was not significantly
different between these 2 treatment groups.
Conclusions and Clinical Relevance—Treatment
with sotalol or mexiletine-atenolol was well tolerated
and efficacious. Treatment with procainamide or
atenolol was not effective. (J Am Vet Med Assoc 2002;221:522–527)
Objective—To determine the type of atrial fibrillation induced by use of 2 pacing protocols during fentanyl and pentobarbital anesthesia before and after administration of atropine and to determine the organization of electrical activity in the left and right atria during atrial fibrillation in German Shepherd Dogs.
Animals—7 German Shepherd Dogs.
Procedures—Extrastimulus and pacedown protocols were performed before and after atropine administration. Monophasic action potential spectral entropy and mean dominant frequency were calculated during atrial fibrillation.
Results—Atrial fibrillation occurred spontaneously in 6 of 7 dogs. All 7 dogs had atrial fibrillation induced. Sustained atrial fibrillation occurred in 13 of 25 (52%) episodes induced by the extrastimulus protocol and in 2 of 12 episodes of atrial fibrillation induced by pacedown. After atropine administration, sustained atrial fibrillation did not occur, and the duration of the nonsustained atrial fibrillation (6 episodes in 2 dogs of 1 to 26 seconds) was significantly shorter than before atropine administration (25 episodes in 7 dogs of 1 to 474 seconds). The left atrium (3.67 ± 0.08) had lower spectral entropy than the right atrium (3.81 ± 0.03), indicating more electrical organization in the left atrium. The mean dominant frequency was higher in the left atrium in 3 dogs.
Conclusions and Clinical Relevance—Atrial fibrillation developed spontaneously and was induced in German Shepherd Dogs under fentanyl and pentobarbital anesthesia. Electrical activity was more organized in the left atrium than in the right atrium as judged by use of spectral entropy.
Objective—To estimate heritabilities and genetic correlations among 4 traits of hip joints (distraction index [DI], dorsolateral subluxation [DLS] score, Norberg angle [NA], and extended–hip joint radiograph [EHR] score) and to derive the breeding values for these traits in dogs.
Animals—2,716 dogs of 17 breeds (1,551 dogs in which at least 1 hip joint trait was measured).
Procedures—The NA was measured, and an EHR score was assigned. Hip joint radiographs were obtained from some dogs to allow calculation of the DI and DLS score. Heritabilities, genetic correlations, and breeding values among the DI, DLS score, NA, and EHR score were calculated by use of a set of multiple-trait, derivative-free, restricted maximum likelihood computer programs.
Results—Among 2,716 dogs, 1,411 (52%) had an estimated inbreeding coefficient of 0%; the remaining dogs had a mean inbreeding coefficient of 6.21%. Estimated heritabilities were 0.61, 0.54, 0.73, and 0.76 for the DI, DLS score, NA, and EHR score, respectively. The EHR score was highly genetically correlated with the NA (r = −0.89) and was moderately genetically correlated with the DI (r = 0.69) and DLS score (r = −0.70). The NA was moderately genetically correlated with the DI (r = −0.69) and DLS score (r = 0.58). Genetic correlation between the DI and DLS score was high (r = −0.91).
Conclusions and Clinical Relevance—Establishment of a selection index that makes use of breeding values jointly estimated from the DI, DLS score, NA, and EHR score should enhance breeding programs to reduce the incidence of hip dysplasia in dogs.