Results of 24-hour ambulatory electrocardiography in dogs undergoing ovariohysterectomy following premedication with medetomidine or acepromazine

OBJECTIVE: To investigate heart rate characteristics in dogs undergoing ovariohysterectomy following premedication with medetomidine or acepromazine. DESIGN: Clinical trial. ANIMALS: 43 client-owned dogs. PROCEDURE: 24-hour ambulatory electrocardiography was performed beginning approximately 1 hour prior to administration of premedications. Dogs were premedicated with medetomidine and butorphanol (n = 21) or acepromazine and butorphanol (22) and, approximately 85 minutes later, were anesthetized with propofol and isoflurane. Electrocardiographic recordings were examined to determine heart rate, cardiac conduction disturbances (ventricular premature complexes and atrioventricular block), and indices of heart rate variability (HRV). RESULTS: Minimum heart rate during the 24-hour recording period was significantly lower among dogs given medetomidine than among dogs given acepromazine, but during the postoperative period, heart rate increased in all dogs as they became physically active. Intraoperative time domain HRV indices were lower and the low frequency-to-high frequency ratio was higher among dogs given acepromazine than among dogs given medetomidine; however, significant differences between groups were no longer seen by 6 hours after surgery. There was no significant difference between groups with regard to the number of ventricular premature complexes or to values of scaling exponent alpha2 (a nonlinear measure of HRV). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that there are greater enhancements in vagally related heart rate indices in medetomidine-treated dogs that may persist until 6 hours after surgery. Despite the low heart rates, dogs given medetomidine showed expected responses to surgery and positional stimuli, and the 2 preanesthetic protocols may not result in different prevalences of ventricular premature complexes.     

Comparison of in-hospital versus 24-hour ambulatory electrocardiography for detection of ventricular premature complexes in mature Boxers

OBJECTIVE: To evaluate the use of in-hospital electrocardiography (ECG) for detection of ventricular premature complexes (VPC), compared with 24-hour ambulatory ECG. DESIGN: Original study. ANIMALS: 188 Boxers > 9 months old; 31 had a history of syncope, and 157 were healthy (no history of syncope). 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 increased. 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.     

Heart rate variability parameters of myxomatous mitral valve disease in dogs with and without heart failure obtained using 24-hour Holter electrocardiography

Time-domain heart rate variability (HRV) parameters and the correlation between echocardiography and Holter examinations in dogs with myxomatous mitral valve disease (MMVD) were determined. Holter examination was also performed at different time frames: an entire 24-hour period, a four-hour period during sleep, and a four-hour period while awake. Ten healthy (control group) and 28 MMVD dogs, 15 with and 13 without heart failure, were evaluated. The SDANN (sd of the mean normal RR intervals for all five-minute segments during 24-hour Holter) and pNN(50) (percentage of differences between adjacent normal RR intervals that are >50 ms computed over 24-hour Holter) variables were significantly lower in the dogs with MMVD heart failure. The differences in HRV between the groups were only detected during the 24-hour evaluation period (P<0.05). There were high correlations (canonical analysis) between Holter and echocardiography examinations when considering pNN(50), SDANN, and LA/AO (left atrial to aortic root ratio) (r=0.92; P<0.05), indicating that both are important in evaluating MMVD dogs. SDANN and pNN(50) are measures of parasympathetic control of the heart, and thus, it is possible to infer that the MMVD dogs exhibit parasympathetic withdrawal during the development of heart failure.     

24-hour Holter-monitoring in the perianaesthetic period in dogs premedicated with dexmedetomidine

Baseline and perianaesthetic 24-hour Holter recordings were carried out in six healthy beagles. After dexmedetomidine premedication anaesthesia was induced with propofol and maintained with propofol infusion or isoflurane for one hour. Dexmedetomidine alone was used as control. The recordings were analysed for ventricular premature complexes (VPC), atrioventricular (AV) blocks and mean heart rate/hour (HR). In most recordings, no ventricular arrhythmias were detected, the maximum frequency being two VPCs/24 h. VPCs were not seen during anaesthesia or during the recovery period. The development of second-degree AV-blocks varied from dog to dog. Most of the heart blocks were seen during the premedication period when bradycardia was most prominent. During the subsequent night, HR was similar between treatments and did not differ from that seen on the baseline recordings. In beagles treated with dexmedetomidine alone or combined with propofol or propofol/isoflurane, ventricular arrhythmias were not detected more frequently than those reported in healthy non-anaesthetised dogs.     

Use of ambulatory electrocardiography for detection of ventricular premature complexes in healthy dogs

OBJECTIVE: To evaluate the use of 24-hour ambulatory electrocardiography (AECG) for the detection of ventricular premature complexes (VPC) in healthy dogs. DESIGN: Case series. 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.     

Effects of clomipramine hydrochloride on heart rate and rhythm in healthy dogs

OBJECTIVE: To determine the effects of clomipramine hydrochloride on heart rate and rhythm in dogs. ANIMALS: 17 healthy Beagles. PROCEDURES: In experiment 1, 8 dogs received placebo or clomipramine (20 mg/kg of body weight, q 24 h, PO) for 7 days in a 2-way crossover design. In experiment 2, 9 dogs were evaluated for 48 hours before and 24 hours after oral administration of clomipramine (4 or 12 mg/kg) in a 2-way crossover design. Electrocardiogram and heart rate were monitored continuously by use of telemetry. RESULTS: A significant diurnal rhythm in heart rate was detected; minimum values were recorded at night. Administration of 20 mg of clomipramine/kg induced a significant reduction in heart rate, with peak effect achieved approximately 12 hours after dosing. Administration of 4 or 12 mg of clomipramine/kg did not result in significant changes in heart rate. Sinoatrial and second-degree atrioventricular block and ventricular escape beats were observed during periods of slow heart rate in more dogs that received clomipramine (3 to 4 of 8 dogs), compared with dogs that received placebo (1 to 2 of 8 dogs), but this difference was not significant. CONCLUSIONS AND CLINICAL RELEVANCE: Short-term administration of clomipramine induced benign cardiovascular effects in dogs rather than the potentially dangerous arrhythmias or tachycardia reported following administration of tricyclic antidepressants to humans. Precautions regarding cardiovascular effects may not be needed for the use of clomipramine in healthy dogs.     

Clinical evaluation of glomerular function: 24-hour creatinine clearance in dogs.

Methods of renal clearance to measure glomerular filtration rate (GFR) were compared with plasma creatinine concentration in clinically normal and partially nephrectomized dogs. Glomerular filtration rate was measured by use of a simple 24-hour creatinine clearance method in 36 normal female Beagles. Mean values were 57.6 +/- 9.3 ml/minute/m2 of body surface or 3.7 +/- 0.77 ml/minute/kg of body weight. Variability of this measurement was considerable, as determined in 4 dogs studied on 4 consecutive days. Glomerular filtration rate was measured in the same 36 dogs while they were under anesthesia, using short clearance periods to compare inulin and endogenous creatinine clearance. Mean values for inulin were 41.8 +/- 13.9 ml/minute/m2 of body surface. A close agreement with creatinine clearance was found (correlation coefficient, 0.998). Mean plasma creatinine concentration was 0.82 (range, 0.5--1.0) mg/100 ml. The value of GFR measurement compared with plasma creatinine concentration was determined in 10 dogs after 75% nephrectomy. Sixty days after partial nephrectomy, GFR was reduced to 61% of normal. Mean plasma creatinine and blood urea nitrogen were 1.2 +/- 0.14 mg/100 ml and 20.4 +/- 7.1 mg/100 ml, respectively. Thus, the detection of reduced renal function may be uncertain when plasma creatinine or blood urea nitrogen are used as a means of evaluating renal function. It was concluded that a simple method of creatinine clearance is a sensitive and useful measurement to detect early or borderline reduction in glomerular function.     

Nervous disorders in dogs associated with levamisole therapy

The onset of nervous disorders associated with levamisole hydrochloride therapy is described in five dogs. Distemper and granulomatous encephalomyelitis were diagnosed in four cases. Possible stimulation of the cellular immune response by levamisole, with resultant secondary tissue damage, was believed to be associated with the time of onset and the severity of these disorders. The neuronal degeneration in the fifth case was not consistent with an inflammatory disorder. The possible role of levamisole in this case is unknown.     

Evaluation of dietary patterns in dogs with cardiac disease

OBJECTIVE: To determine the dietary patterns and intake of nutrients of concern in dogs with cardiac disease. DESIGN: Prospective study. ANIMALS: 82 dogs with dilated cardiomyopathy (DCM) or chronic valvular disease. PROCEDURE: Owners of dogs were contacted and given a standardized telephone questionnaire regarding diet and a 24-hour food recall to determine daily intake of calories, protein, fat, sodium, potassium, and magnesium. RESULTS: Among the 82 dogs, 71% had no congestive heart failure (CHF), and 29% had CHF or a history of CHF. Sixty-one percent of dogs had concurrent diseases. Anorexia was or had been evident in 34% of dogs and was significantly more common in the CHF group and in dogs with DCM. Most dogs (92%) received some treats and table food, with a median percentage of daily calories from treats of 19% (range, 0% to 100%). Most owners (57%) that administered pills used human or pet foods for pill administration. Most dogs ate more than the Association of American Feed Control Officials (AAFCO) minimum values for fat and protein. Daily sodium intake varied from 14 to 384 mg/100 kcal, compared with the AAFCO minimum of 17 mg/100 kcal. A median of 25% of total daily sodium came from treats and table food (range, 0% to 100%). Dogs with CHF ate significantly more sodium, compared with dogs with no CHF. CONCLUSIONS AND CLINICAL RELEVANCE: Dietary intake for dogs with cardiac disease is highly variable and often not optimal.     

Circadian variations in salivary chromogranin a concentrations during a 24-hour period in dogs

The purpose of this study was to determine if salivary chromogranin a secretion in dogs exhibits a circadian rhythm. Saliva sampling was performed during three different sessions occurring in three nonconsecutive 24-h periods. Sixteen healthy adult beagle dogs (8 males and 8 females) were moved to a sampling room and housed individually in cages. Saliva samples were obtained every 4 h from 12:00 p.m. to 12:00 p.m. the following day. In the interest of habituation, saliva was obtained hourly from each dog 3 h before the experiment was started. Salivary chromogranin A concentrations were measured using an enzyme-linked immunosorbent assay. No circadian rhythm was detected for salivary chromogranin A secretion, and no differences in salivary chromogranin A concentrations measured every 4 h were demonstrated during the 24-h cycle in dogs.     

Results of ambulatory electrocardiography in overtly healthy Doberman Pinschers with echocardiographic abnormalities

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. Twenty-eight 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.     

Evaluation of platelet function in dogs with cardiac disease using the PFA‐100 platelet function analyzer

Background: Cardiac disease has the potential to alter platelet function in dogs. Evaluation of platelet function using the PFA‐100 analyzer in dogs of multiple breeds and with a broad range of cardiac conditions would help clarify the effect of cardiac disease on platelets. Objectives: The objective of this study was to assess differences in closure time (CT) in dogs with cardiac disease associated with murmurs, when compared with that of healthy dogs. Methods: Thirty‐nine dogs with cardiac murmurs and turbulent blood flow as determined echocardiographically were included in the study. The dogs represented 23 different breeds. Dogs with murmurs were further divided into those with atrioventricular valvular insufficiency (n=23) and subaortic stenosis (n=9). Fifty‐eight clinically healthy dogs were used as controls. CTs were determined in duplicate on a PFA‐100 analyzer using collagen/ADP cartridges. Results: Compared with CTs in the control group (mean±SD, 57.6±5.9 seconds; median, 56.5 seconds; reference interval, 48.0–77.0 seconds), dogs with valvular insufficiency (mean±SD, 81.9±26.3 seconds; median, 78.0 seconds; range, 52.5–187 seconds), subaortic stenosis (71.4±16.5 seconds; median, 66.0 seconds; range, 51.5–95.0 seconds), and all dogs with murmurs combined (79.6±24.1 seconds; median, 74.0 seconds; range, 48.0–187 seconds) had significantly prolonged CTs (P<.01). Conclusions: The PFA‐100 analyzer is useful in detecting platelet function defects in dogs with cardiac murmurs, most notably those caused by mitral and/or tricuspid valvular insufficiency or subaortic stenosis. The form of turbulent blood flow does not appear to be an important factor in platelet hypofunction in these forms of cardiac disease.     

Toxicity and tissue residue depletion of levamisole hydrochloride in young goats

Toxicity and tissue residue depletion studies were conducted in young goats, using an oral drench formulation of levamisole hydrochloride. In the target animal toxicity study, 3 groups of 5 goats each were given levamisole orally to provide approximately 11.88, 23.76, or 35.64 mg of levamisole HCl/kg/d for 3 consecutive days; a fourth group of 5 goats served as untreated controls. Blood samples were taken for analysis of levamisole 1 day prior to dosing and 1, 2, 3, 4, and 7 days following the third dose. At the 35.64-mg/kg dose, 2 of 5 goats responded with typical cholinergic signs of toxicosis on each of the 3 days of dosing. The times for the onset of clinical signs of toxicosis ranged from 18 to 63 minutes, with an average duration of 32 minutes. Administration of 23.76 mg of levamisole HCl/kg resulted in hyperactive behavior in 1 of 5 goats only on the first day of dosing; no abnormal behavior was observed in any of the 5 goats following the second or third dose of levamisole HCl at 23.76 mg/kg. Untoward effects were not seen in the 5 goats dosed at 11.88 mg of levamisole HCl/kg or in the controls during the 3-day dosing period or in the following 7-day observation period. Overall, the observed signs of toxicosis did not become more severe, affect more goats, or persist for a longer period on subsequent dosing days.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacokinetics of procainamide hydrochloride in dogs

Pharmacokinetics of procainamide hydrochloride were studied in 2 groups of dogs. In a group of 6 dogs, procainamide was administered IV at a small dose of 8 mg/kg (group 1), and blood samples were obtained for 3.5 hours. In another group of 6 dogs, procainamide was administered IV and orally at an average dose of 25.5 mg/kg (group 2) in a crossover manner. Blood samples were obtained for 48 hours. In 2 dogs (previously used in part II), N-acetylprocainamide (NAPA) was administered IV at a dose of 10 mg/kg. Plasma samples were assayed for procainamide by fluorescence polarization immunoassay, and NAPA samples were assayed by high-performance liquid chromatography. In group 1, the elimination of procainamide was described by a 1-compartment, open pharmacokinetic model. The elimination half-life was 2.43 hours, the apparent volume of distribution was 1.44 L/kg, and the systemic clearance was 0.412 L/kg/hr. In group 2, 2 of the 6 dogs were described by a 1-compartment model, and 4 of the 6 dogs were described with a 2-compartment pharmacokinetic model. The elimination half-life for the IV dosage was 2.85 hours, the apparent volume of distribution was 2.13 L/kg, and the systemic clearance was 0.519 L/kg/hr. For the orally administered dose, the bioavailability was 85%, and the absorption half-life was 0.5 hours. There was no evidence of acetylation of procainamide to NAPA or deacetylation of NAPA to procainamide. The estimated elimination half-life of NAPA was 4.7 hours.