Ventricular Arrhythmias in Dogs Undergoing Splenectomy: A Prospective Study

Fifty dogs undergoing splenectomy for splenic masses (n = 40), torsion of the splenic pedicle (n = 5), and immune-mediated disease (n = 5) were evaluated preoperatively and postoperatively for ventricular arrhythmias and the relationship between ventricular arrythmia and splenic disease. The ability of 1 -minute electrocardiograms recorded every 6 hours (ECGs/q6hr) to detect ventricular arrythmia was compared with continuous 48-hour Holter monitoring. Based on continuous Holter monitoring, splenectomized dogs had a high incidence (22 of 50) of rapid ventricular tachycardia. The incidence of rapid ventricular tachycardia was significantly higher in dogs with ruptured splenic masses (16 of 23) than without rupture (1 of 17) ( P < .001). When the results of ECG/q6hr were compared with the results of continuous Holter monitoring, ECG/q6hr was normal in 29% (4 of 14) of dogs with rapid ventricular tachycardia at > 3,000 ventricular extrasystoles (VE)/hr; 50% (4 of 8) of dogs with rapid ventricular tachycardia at 1,000 to 3,000 VE/hr and 100% (6 of 6) of dogs with 10 to 300 VE/hr without rapid ventricular tachycardia. Although dogs undergoing splenectomy had a high incidence of ventricular arrythmias, one-minute ECGs/q6h were unreliable for detection of ventricular arrythmias even when high-frequency extrasystoles occurred.     

Retrospective analysis of the clinical utility of ambulatory electrocardiographic (Holter) recordings in syncopal dogs: 44 cases (1991-1995)

The objective of this study was to evaluate retrospectively the clinical utility of ambulatory (Holter) electrocardiographic monitoring in syncopal dogs and to compare the Holter recording with the clinic electrocardiogram (ECG) in these animals. Fifty Holter reports and 44 medical records from 44 dogs were evaluated. A syncopcal episode occurred during monitoring in 24% of the recordings. No obvious relationship was found between the frequency of syncope occurring before Holter recording and the likelihood of a dog having an episode during recording. Holter recordings were helpful in establishing a diagnosis 42% of the time, but no relationship was detected between the frequency of episodes occurring before Holter recording and the likelihood of a diagnostically useful Holter. An arrhythmia was ruled out as the cause of syncope in 12% of the recordings and was implicated as the cause of syncope in 30% of recordings. Of these, 20% were ventricular tachyarrhythmias and 10% were bradyarrhythmias including pacemaker failure. Ambulatory electrocardiographic recordings led to a therapeutic change in 38% of cases. A comparison of the Holter recordings and clinic ECGs documented the expected increased sensitivity for Holter detection of arrhythmias. The average clinic ECG heart rate consistently exceeded the average Holter heart rate with a mean difference between the average heart rates recorded by the two techniques of 31 bpm (range -8-87 bpm).     

Implantation of permanent transvenous endocardial pacemaker in a dog with atrioventricular block

A 10-year old male mongrel dog was presented to the University Veterinary Teaching Hospital with a two-month history of episodic syncope. Twenty-four hr Holter electrocardiographic (ECG) recording revealed frequent episodes of advanced atrioventriculer block with long periods of ventricular asystole. The cause of syncope was determined to be Adams-Stokes syndrome exhibited bradyarrhythmia. After the animal failed to respond to medical therapy, permanent transvenous pacemaker implantation was performed. Postoperative Holter ECG showed 100 beat per min programmed pacemaker rhythm, which indicated successful capture of the artificial pacing. The dog recovered smoothly from the operation and syncopal episodes completely disappeared. Six months after the surgery, no complications were observed and the dog's quality of life has dramatically improved.     

Holter monitoring in clinically healthy Cavalier King Charles Spaniels, Wire-haired Dachshunds, and Cairn Terriers

Background: Few reported studies describe normal values from 24‐hour ECG (Holter) recordings of small breed dogs. Objectives: To investigate influence of breed, age, sex, body weight, degree of recording artifact, and mitral valve prolapse (MVP) on Holter recordings of 3 breeds of small dogs that have differing predispositions for myxomatous mitral valve disease. The study also assessed if heart rate (HR) at clinical examination (HRex) was associated with HR during Holter monitoring and evaluated the reproducibility of Holter variables. Animals: Fifty clinically healthy, privately owned dogs of the breeds Cavalier King Charles Spaniel (CKCS), Wire‐haired Dachshund (wD), or Cairn Terrier (CT). Methods: Prospective, longitudinal observational study. Dogs were recruited for clinical examination, echocardiography, and Holter monitoring. In 8 CKCS, Holter recordings were performed twice with a 7‐day interval. Arrhythmia and heart rate variability (HRV) analysis (time and frequency domain analysis) were performed on Holter recordings. Results: Fifteen out of 27 Holter derived variables were significantly associated with breed (P < .03), but not with age (P > .7), sex (P > .2), body weight (P > .7), degree of recording artifact (P > .4), or MVP (P > .6). During Holter recording, minimum (P= .0001) and mean HR (P= .0001) were higher in CKCS compared with wD. CKCS had significantly lower values than wD, CT, or both in 10 out of 13 HRV variables (P < .03). Minimum and mean HR during Holter recording were correlated with HRex (r= 0.55, P= .0003). HR and time domain variables had a coefficient of variation <10%. Conclusions and Clinical Importance: There is an influence of breed on Holter‐derived variables in 3 breeds of small dogs. Arrhythmia and HRV analysis can be performed on 24‐hour ambulatory ECG (Holter) recordings. Arrhythmia analysis includes HR measurements and identification of arrhythmias.     

Evaluation of spontaneous variability in the frequency of ventricular arrhythmias in Boxers with arrhythmogenic right ventricular cardiomyopathy

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). DESIGN: Prospective study. ANIMALS: 10 Boxers with ARVC with prior ambulatory ECG recordings that included > or = 500 ventricular premature complexes/24 h. 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 < or = 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.     

Plication of the free wall of the left ventricle in dogs with doxorubicin-induced cardiomyopathy

OBJECTIVE: To evaluate plication of the free wall of the left ventricle, which reduces the left ventricular area and volume, as a method to improve the left ventricular systolic function without cardiopulmonary bypass. ANIMALS: 8 mixed-breed adult dogs. PROCEDURE: Dilated cardiomyopathy (DCM) was induced in each dog by administration of doxorubicin (30 mg/m2, i.v., q 21 d for 168 days).Two dogs died during induction of cardiomyopathy. Plication surgery was performed in 4 dogs. Two dogs did not ondergo to surgery (control group). Values for cardiac output (CO), 2-dimensional and M-mode echocardiography, arterial blood pressure, electrocardiography, blood cell counts, and serum biochemical analyses were recorded after induction of DCM (baseline) and 1, 2, 7, 15, 21, 30, 60, 90, 120, 150, and 180 days after plication surgery. Ambulatory ECG (Holter) recordings were conducted for 24 hours on the day of surgery. RESULTS: 1 dog died after plication surgery. The remaining dogs undergoing ventricular plication had a significant improvement in CO, ejection fraction, and fractional shortening and reductions of left ventricular area and volume after surgery. Electrocardiographic and Holter recordings revealed premature ventricular complexes, which resolved without treatment during the first week after surgery. Clinical condition of the control dogs declined, and these 2 dogs died approximately 40 days after induction of cardiomyopathy. CONCLUSIONS AND CLINICAL RELEVANCE: Plication of the free wall of the left ventricle improved left ventricular systolic function in dogs with doxorubicin-induced cardiomyopathy. Additional studies are needed to evaluate its application in dogs with naturally developing DCM.     

Holter monitoring in 36 dogs with myxomatous mitral valve disease

Objective Describe the presence of arrhythmias in dogs with myxomatous mitral valve disease (MMVD) and the potential association with class of heart failure and left atrial enlargement. Compare the standard electrocardiogram (ECG) with Holter monitoring for assessing heart rate (HR). Experimental procedure The study group of 36 dogs weighing less than 20 kg was divided into MMVD and no clinical signs (preclinical) or MMVD and clinical signs (clinical). A standard echocardiogram, ECG and 24-h Holter recording were obtained in all dogs. Results Minimum and mean Holter HRs were higher in the clinical group than in the preclinical group. Clinical dogs had more ventricular arrhythmias than preclinical dogs. An enlarged left atrium was associated with the presence of more supraventricular arrhythmias. Conclusions Arrhythmias are a common finding in dogs with MMVD and Holter monitoring is a reliable tool for both HR monitoring and diagnosis.     

The vasovagal tonus index as a prognostic indicator in dogs with dilated cardiomyopathy

Objectives : To investigate the prognostic and diagnostic value of heart rate variability (HRV) using the vasovagal tonus index (VVTI) in dogs suffering from idiopathic dilated cardiomyopathy (DCM). Methods : Electrocardiographic (ECG) recordings of 369 patients presented to a referral centre between 1993 and 2006 were reviewed. Results : VVTI values were calculated from 132 dogs. Lower VVTI values were found in patients in International Small Animal Cardiac Health Council (ISACHC) heart failure (HF) class 2 and 3 compared with class 1. VVTI was found to be positively correlated with survival time (ST) in class 2 and 3 patients. When a cut‐off value of 7·59 for VVTI was used, the test could differentiate patients in ISACHC HF class 1 versus 2 and 3 with a sensitivity of 89 per cent and a specificity of 62·5 per cent. The ST for patients with VVTI values less than 7·59 was significantly lower. Clinical Significance : The VVTI is a useful index, obtained from a standard ECG recording that estimates HRV in dogs and does not require any specific equipment for its calculation. It can be useful as a diagnostic tool to assess the severity of HF and is a useful prognostic tool in dogs with DCM.     

Spontaneous activities measured continuously by an accelerometer in beagle dogs housed in a cage

Spontaneous activities in 10 beagle dogs housed in an individual cage were recorded continuously for 2 hr by an accelerometer fixed to dogs and by a video camera. The responses of the accelerometer were compared to movements identified from the video tapes. We found that gross differentiation of quantitative spontaneous activities might be possible by using only the accelerometer if the threshold of the accelerometer and the amount of acceleration volume were set adequately: the responses of the accelerometer at the threshold of 0.10 G with the acceleration number of 251 or more revealed only movements of the whole-body, and those at the threshold of 0.02 G all movements including changes of the part(s) of the body.     

Validation of 2 techniques for electrocardiographic recording in dogs and cats

BACKGROUND: Standard electrocardiographic (ECG) recording in the dog and cat is commonly performed in right lateral recumbency, by connecting the ECG leads to the skin of the patient via metallic alligator clips. The jaws of the alligator clips are usually filed or flattened to reduce their uncomfortable pressure on the patient's skin. However, filed and flattened alligator clips can occasionally lose their grip to the skin, causing lead detachment during standard ECG recording. HYPOTHESIS: The aim of the study was to validate two novel ECG recording techniques ("gel" and "pads"). ANIMALS: Six-lead standard ECG recording was obtained from 42 dogs and 40 cats using the standard technique, as well as the two novel methods. METHODS: Measurements were taken of the amplitude and duration of P waves and QRS complexes, duration of PQ and QT intervals, and mean electrical axis (MEA). In each recording, five representative complexes were measured, and the results were averaged for each parameter. RESULTS: A good quality ECG recording was obtained with all the three different techniques, although a degree of wandering trace was observed in one third of cats with the "pads" technique. Bland-Altman analysis showed good agreement between the ECG values recorded with the two novel techniques and those recorded with the standard traditional technique. Furthermore, the observed differences were not clinically relevant, except for the R wave amplitude recorded with the "pads" method in cats (-0.35 to 0.37 mV). CONCLUSIONS AND CLINICAL IMPORTANCE: In conclusion, this study supports the reliability and clinical validity of the "gel" and "pads" techniques for ECG recording both in the dog and the cat, with some limitations for the "pads" technique in cats.     

Electrocardiographic assessment of antianxiety medication in dogs and correlation with serum drug concentration

OBJECTIVES: To determine effects of tricyclic antidepressants (TCA) on the ECG of dogs treated for behavioral conditions and to examine correlations between ECG findings and serum concentrations of these medications. DESIGN: Repeated-measures study. ANIMALS: 39 client-owned dogs with behavioral problems. PROCEDURE: Two groups of dogs with behavioral problems were evaluated. In group 1 (n = 20), ECG tracings were recorded before starting treatment with TCA and again after treatment for > or = 1 month. Dogs in group 2 were already on long-term maintenance amounts of antianxiety medication when ECG tracings were recorded and serum concentrations of medications were obtained. RESULTS: Significant differences were not detected for dogs in group 1 between ECG values measured before and after TCA administration. The ECG values for dogs in group 2 did not differ significantly from the mean of group-1 dogs before receiving medication or from the reference range used at our facility. Duration of the P wave had a significant positive correlation with serum concentrations of clomipramine but significant negative correlation with serum concentrations of amitriptyline. The QT interval corrected for heart rate had a significant negative correlation with serum concentrations of amitriptyline. CONCLUSIONS AND CLINICAL RELEVANCE: Amitriptyline and clomipramine administered at standard dosages apparently do not cause ECG abnormalities in healthy dogs with behavioral problems. These medications should be used cautiously in dogs with conduction abnormalities, and clinicians should periodically monitor ECG and use good clinical judgment to weigh risks and benefits of medications for the safety of each dog.     

Change of diurnal heart rate patterns during pregnancy and lactation in dogs (Canis familiaris)

Pregnancy and lactation involve great demands on the cardiovascular system. The purpose of this study was to investigate how the heart rate and diurnal heart rate pattern change when dogs become pregnant or lactate. Five clinically healthy female beagle dogs were mated, and delivered three to seven healthy puppies. The heart rate was investigated with 24-h ECG (Holter) once during anoestrus, at 3, 5, 7 and 9 weeks of pregnancy, and at week 4 postpartum (lactation). However, at 9 weeks, the ECG could not be recorded for the fully 24 h in 4 of 5 dogs, because labour started and the dogs then appeared disturbed by the recordings. The results at this date are not included in the statistical comparison. The heart rate increased progressively during pregnancy and was still elevated at 4 weeks of lactation. During late pregnancy the difference in heart rates between daytime and nighttime became smaller, but the heart rate was significantly higher in daytime in all periods. In conclusion, the increased heart rates during pregnancy and lactation reflect increased demands on the cardiovascular system and may be important to consider in clinical practice.     

Combination Therapy with Digoxin and Diltiazem Controls Ventricular Rate in Chronic Atrial Fibrillation in Dogs Better than Digoxin or Diltiazem Monotherapy: A Randomized Crossover Study in 18 Dogs

Background: Atrial fibrillation (AF) with excessively high ventricular rates (VR) occurs in dogs with advanced heart disease. Rate control improves clinical signs in these patients. Optimal drug therapy and target VR remain poorly defined.
Hypothesis: Digoxin-diltiazem combination therapy reduces VR more than either drug alone in dogs with high VR AF.
Animals: Eighteen client-owned dogs (>15 kg) with advanced heart disease, AF, and average VR on 24-hour Holter > 140 beats per minute (bpm).
Methods: After baseline Holter recording, dogs were randomized to digoxin or diltiazem monotherapy, or combination therapy. Repeat Holter evaluation was obtained after 2 weeks; dogs were then crossed over to the other arm (monotherapy or combination therapy) for 2 weeks and a third Holter was acquired. Twenty-four hour average VR, absolute and relative VR changes from baseline, and percent time spent within prespecified VR ranges (>140, 100–140, and <100 bpm) were compared. Correlations between serum drug concentrations and VR were examined.
Results: Digoxin (median, 164 bpm) and diltiazem (median, 158 bpm) decreased VR from baseline (median, 194 bpm) less than the digoxin-diltiazem combination (median, 126 bpm) ( P < .008 for each comparison). With digoxin-diltiazem, VR remained <140 bpm for 85% of the recording period, but remained >140 bpm for 88% of the recording period with either monotherapy. Serum drug concentrations did not correlate with VR.
Conclusions and Clinical Importance: At the dosages used in this study, digoxin-diltiazem combination therapy provided a greater rate control than either drug alone in dogs with AF.     

Electrocardiographic findings in dogs with motor vehicle-related trauma

Motor vehicle-related injury is the most common form of trauma incurred by dogs, and cardiac arrhythmias are a well-recognized complication. Although posttraumatic arrhythmias are often observed, little is known regarding their frequency. This study utilized continuous ambulatory electrocardiography (i.e., Holter monitoring) to describe the cardiac rhythm disturbances in 30 dogs sustaining trauma in motor vehicle accidents. Ventricular ectopy was identified by Holter monitoring in 29 of 30 dogs, although the initial electrocardiogram (EKG) only documented ventricular ectopic complexes (VECs) in four dogs. Ventricular ectopy was infrequent in most dogs (i.e., 62% of the dogs had less than 100 VECs per day for the entire study), but 16% developed frequent arrhythmias (greater than 4,000 VECs per day). In all cases, the VECs were observed within 24 hours of injury. Forty-three percent of dogs had at least one episode of ventricular tachycardia, including several dogs that had an overall infrequent rate of VECs (i.e., less than 100 or 100 to 1,000 VECs per day). Although baseline EKGs are useful in identifying arrhythmias in most dogs, the length of the recording should be increased to improve the likelihood of observing an abnormal EKG event. Most importantly, additional EKGs should be obtained or continuous EKG monitoring should be performed in dogs that display clinical signs that could be attributed to ventricular arrhythmias.     

Evaluation of an accelerometer for at-home monitoring of spontaneous activity in dogs

OBJECTIVE:To determine the correlation between activity as measured by an accelerometer and videographic measurements of movement and mobility in healthy dogs. ANIMALS: 4 healthy dogs. PROCEDURES: After determination that accelerometers had good agreement, 5 identical accelerometers were used simultaneously to test their output at 8 locations (rotated among collar, vest, and forelimb stocking locations) on each dog. Movement and mobility for each dog were recorded continuously with a computerized videography system for 7-hour sessions on 4 consecutive days. Accelerometer values were combined into 439 fifteen-minute intervals and compared with 3 videographic measurements of movement and mobility (distance traveled, time spent walking > 20 cm/s, and time spent changing position by > 12% of 2-dimensional surface area during 1.5 seconds). RESULTS: 96% of values compared between the most discordant pair of accelerometers were within 2 SDs of the mean value from all 5 accelerometers. All mounting locations provided acceptable correlation with videographic measurements of movement and mobility, and the ventral portion of the collar was determined to be the most convenient location. CONCLUSIONS AND CLINICAL RELEVANCE: Use of an accelerometer was adequate for at-home activity monitoring, an important end point in clinical trials of treatment for chronic disease, and provided information about daily activity that is unattainable by other methods.     

Effect of body position on the 6-lead ECG of dogs

ECGs recorded from dogs show characteristic morphology and changes in morphology with various disease states. These changes are determined by comparing individual recordings to reference ranges established from recordings obtained from normal dogs in right lateral (RL) recumbency. Using these reference ranges for ECGs recorded from dogs in other positions may not be valid. We compared ECG complexes from 39 normal dogs obtained in RL, left lateral (LL), and standing (ST) body positions. ECGs from dogs in ST position showed increased Q-wave and R-wave amplitudes in leads I and II, increased R-wave and S-wave amplitudes in leads aVR and aVL, and decreased R-wave and S-wave amplitudes in lead III when compared with recordings obtained in RL position. ECGs from dogs in LL position showed increased R-wave amplitude in leads II, III, and aVF and S-wave amplitude in lead aVL but decreased R-wave amplitude in lead aVR when compared with recordings obtained in RL position. The mean electrical axis (MEA) shifted to the left in ST position but remained within the normal range in LL position. We determined that both a change in the relative position of the recording electrodes with respect to the heart as well as a change in intrathoracic cardiac position contributed to these changes. P-wave amplitude, P-R and S-T intervals, and QRS complex durations remained unaltered by changes in body position. Our findings indicate that ECGs of dogs recorded in RL, LL, and ST positions yield dramatically different results, and investigators should use position-specific reference ranges to minimize potential misinterpretation of ECG results.     

Effects of the application of neck pressure by a collar or harness on intraocular pressure in dogs

The effect on intraocular pressure (IOP) from dogs pulling against a collar or a harness was evaluated in 51 eyes of 26 dogs. The force each dog generated while pulling against a collar or a harness was measured. Intraocular pressure measurements were obtained during application of corresponding pressures via collars or harnesses. Intraocular pressure increased significantly from baseline when pressure was applied via a collar but not via a harness. Based on the results of the study, dogs with weak or thin corneas, glaucoma, or conditions for which an increase in IOP could be harmful should wear a harness instead of a collar, especially during exercise or activity.     

Correlations among time and frequency measures of heart rate variability recorded by use of a Holter monitor in overtly healthy Doberman pinschers with and without echocardiographic evidence of dilated cardiomyopathy.

OBJECTIVE: To determine correlations between time-domain 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 very-low-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.     

Polymorphism,coupling interval and prematurity index in dogs with degenerative mitral valve disease and ventricular arrhythmias

Ventricular arrhythmias (VA) are a recognized concern in dogs with degenerative mitral valve disease (DMVD). The coupling interval (CI) and the prematurity index (PI) have been shown to accurately differentiate between benign and malignant VA in people, where ventricular arrhythmias are known to be associated with an increased risk of development of signs of heart failure or sudden death. In this study, we characterized ventricular arrhythmias in dogs with symptomatic and asymptomatic DMVD. Seventy dogs with naturally-occurring DMVD and ventricular arrhythmias were retrospectively studied. A cross-sectional investigation including dogs with either symptomatic (stages C/D; n?=?41) or asymptomatic (stages B1/B2; n?=?29) DMVD was performed. Electrocardiographic tracings were reviewed to calculate both the CI and PI. In eight dogs these indices were compared with those obtained from both a Holter recording and a standard ECG tracing and no statistical differences were found (CI, p?=?0.97; PI, p?=?0.17). Even though CI and PI were determined in all animals enrolled in the study, VPC characteristics were only compared between symptomatic and asymptomatic dogs when a 24-h Holter recording was available (n?=?49). The PI was different (p?=?0.01) between symptomatic (0.65?±?0.17) and asymptomatic (0.56?±?0.18) dogs, but CI was considered similar (p?=?0.91). Also, the symptomatic dogs had more polymorphic VPC (p?=?0.002) and supraventricular arrhythmias (p?=?0.0002) than the asymptomatic animals. Polymorphism, and repeating patterns of ventricular premature complexes, were characteristics frequently present in overtly symptomatic animals affected by mitral endocardiosis.     

Toxicity in Doberman Pinchers with Ventricular Arrhythmias Treated with Amiodarone (1996–2005)

Background: Asymptomatic Doberman Pinschers with dilated cardiomyopathy (DCM) often die suddenly owing to ventricular tachycardia that degenerates into ventricular fibrillation. A safe and effective antiarrhythmic drug treatment is needed. This will require a large, well-controlled, prospective study.
Hypothesis: Amiodarone toxicity is common in Dobermans with occult DCM and ventricular tachyarrhythmias refractory to antiarrhythmia therapy. Infrequent monitoring of hepatic function is inadequate. Frequent monitoring may be useful to determine dogs in which the dosage should be decreased or the drug withdrawn.
Methods: Medical records from the University of Georgia and Cornell University were searched for Doberman Pinschers diagnosed with preclinical DCM that received amiodarone for severe ventricular arrhythmias refractory to other antiarrhythmic agents. Echocardiographic data, Holter recording data, hepatic enzyme serum activity, and serum amiodarone concentrations were recorded. The presence of clinical signs of toxicity was recorded. Serum amiodarone concentrations were obtained in some dogs.
Results: Reversible toxicity was identified in 10 of 22 (45%) dogs.
Conclusion and Clinical Importance: Adverse effects from amiodarone were common and were, in part, dosage related. Patients should be monitored for signs of toxicity and liver enzyme activity should be measured at least monthly.