Unipolar thoracic electrocardiograms in which P waves of relative uniformity occur in male horses

Bipolar and unipolar limb leads and unipolar thoracic lead ECG were obtained from 100 male crossbred horses. P-wave morphologic features were classified according to positivity negativity and monopolarity dipolarity, and the percentage of horses that had P waves of a given morphologic class in each lead was calculated. P-Wave morphologic features of 4 precordial leads were most uniform, with greater than 80% of the horses having a single configuration.     

Balloon dilation of oesophageal strictures in two horses

Oesophageal strictures in 2 horses with chronic recurrent oesophageal obstruction or choke was diagnosed by endoscopy and contrast radiography. Balloon dilation of the strictures was performed under endoscopic and fluoroscopic guidance. Follow‐up endoscopic and radiological examinations performed 6 weeks after the procedure showed clear dilation of the strictures. Both horses did not have any recurrence during follow‐up periods of 10 and 12 months.     

Treatment of cervical oesophageal rupture in horses

Oesophageal rupture in horses has only been previously described in detail in isolated case reports. The objectives of this study were to describe the clinical findings, specific treatment and outcome of oesophageal rupture in horses. Medical records of horses diagnosed with oesophageal rupture between 1994–2008 were reviewed. Clinical findings, treatment and outcome were recorded. Seven horses with cervical oesophageal perforations were included in the study. Two horses were subjected to euthanasia without treatment and 5 were treated surgically. Treatment involved a fasciotomy of the cervical musculature and oesophageal tube placement. Three of 5 horses survived long‐term (>one year). Our study showed that surgical treatment of cervical oesophageal rupture involving fasciotomy and oesophagostomy tube placement can be successful with 3/5 of treated horses surviving more than one year.     

Relationship of heart rate and electrocardiographic time intervals to body mass in horses and ponies

ObjectivesTo investigate the relationship of heart rate (HR) and ECG time intervals to body weight (BWT) in healthy horses and ponies. We hypothesized that HR and ECG time intervals are related to BWT.Animals250 healthy horses of >30 breeds; 5.5 (1–30) y [median (range)]; 479 (46–1018) kg.MethodsProspective study. Standard base-apex ECGs were recorded while the horses were standing quietly in a box stall. Mean HR over 15 s was calculated and RR interval, PQ interval, QRS duration, and QT interval were measured by a single observer.QT was corrected for differences in heart rate using Fridericia's formula (QT_cf = QT/³√RR). The relationship between ECG variables and BWT, age, sex, and RR interval was assessed using multivariate backward stepwise regression analyses. Goodness of fit of the model was improved when using log(BWT) compared to BWT. Body weight was overall the strongest predictor of HR and ECG time intervals. Therefore, only log(BWT) was included as an independent variable in the final model. The level of significance was p = 0.05.ResultsHR (R² = 0.21) showed a significant negative relationship and PQ (R² = 0.53), QRS (R² = 0.23), QT (R² = 0.14), and QT_cf (R² = 0.02) showed significant positive relationships to log(BWT).ConclusionsSmall equine breeds undergoing routine ECG recordings have slightly faster heart rates and shorter ECG time intervals compared to larger equine breeds. Although the magnitude of absolute differences may be small, body weight needs to be considered among other factors when comparing HR and ECG time intervals to normal ranges in horses.     

Oesophageal disorders in horses: Retrospective study of 39 cases

Oesophageal diseases are less frequently reported in equine veterinary practice in comparison with other alimentary pathologies. This paper describes the prevalence, age, breed and sex distribution, the duration of clinical presentation before admission, the diagnosis, aetiology, treatment course, complications, length of hospitalisation, and the short‐term and long‐term survival of 39 cases with equine oesophageal disorders at a referral clinic. Prevalence of oesophageal disorders was significantly higher in the group of horses up to 4 years of age in comparison with other age groups. The most common oesophageal disorder was simple obstruction represented by 22/39 cases (56.41%). The common complications of the oesophageal disorder were oesophagitis (16/39, 41.02%) and aspiration pneumonia (11/39, 28.20%); 31/39 (79.49%) of all oesophageal cases survived up to clinical discharge. Long‐term survival was 65.78% in this group of cases.     

Management and complications associated with treatment of cervical oesophageal perforations in horses

Six horses were evaluated for colic and anorexia, choke or suspected oesophageal rupture with and without tracheal laceration. Clinical findings were variable, but a painful ventral neck swelling was noted in all cases. Two of the horses had signs of dehydration and sepsis. Additional findings included evidence of previous trauma over the trachea and oesophagus, ventral neck abscessation, choke and aspiration pneumonia. A diagnosis of oesophageal perforation was made using endoscopy. Two horses were subjected to euthanasia without treatment. All horses where treatment was attempted received debridement of the oesophageal perforation and surrounding tissues with or without surgical closure of the oesophageal defect. Other therapies included broad spectrum antimicrobials, anti‐inflammatory drugs, fluid and nutritional support as well as additional therapeutics for sepsis and individual complications. Complications included diverticulum formation, thrombophlebitis, diarrhoea, laryngeal hemiplegia, azotaemia, aspiration pneumonia, oesophageal obstruction, weight loss and laminitis. All 4 treated horses recovered from the oesophageal perforation and are able to eat a normal diet. Two of the 4 horses have had infrequent episodes of recurrent choke. Oesophageal rupture should be considered as a differential diagnosis for horses with a painful swelling of the ventral neck. With surgical debridement and adequate supportive care, oesophageal perforation cases can have a fair to good long‐term survival, although chronic complications can occur, therapy is prolonged, and a significant economic commitment is required.     

Electrocardiographic Parameters in the Normal Lactating Holstein Cow

Electrocardiographic parameters in the normal lactating Holstein cow have been measured, computed and analyzed. The study was conducted on 32 animals of a mean age of 4.7 years. The recordings of the 12 leads (I, II, III, aVR, aVL, aVF, CV₆LU, CV₆LL, CV₆RL, CV₆RU, V₁₀ and base-apex) were made with a three channel electrocardiograph calibrated at 20 mm/mV and 25 mm/s. Conduction parameters, waves, intervals and segments have been measured. The recordings were analyzed as to shape, polarity and amplitude of the P and T waves and the components of the QRS complex. The results are discussed in respect to the morphophysiological characterestics of the bovine heart.     

Conservative treatment of acquired oesophageal strictures by endoscopic‐guided balloon dilation in two horses

Oesophageal stricture is an uncommon condition in horses that results in an obstructive syndrome with regurgitation of food and possible aspiration pneumonia. Currently, in both human and small animal practice, one of the preferred treatment options for oesophageal strictures consists of pneumatic or hydrostatic balloon dilation. The aim of this article is to report 2 cases of severe oesophageal stricture in the horse, successfully treated with endoscopic‐guided hydrostatic balloon dilation.     

Electrocardiographic parameters of free-ranging roe deer (Capreolus capreolus).

Electrocardiographic parameters were measured in 28 free-ranging roe deer (Capreolus capreolus). The electrocardiograms (ECGs) were recorded in base-apex lead, standard bipolar limb leads (I, II, III), and augmented unipolar limb leads (aVR, aVL, aVF). Morphology and amplitude of P waves, QRS complexes, and T waves were analyzed in all seven leads. Cardiac rhythm, heart rate, and durations of P, QRS, and T waves, PR interval, QTc interval, and ST segment were calculated in the base-apex lead. The mean electrical axis for each individual was determined from the net amplitude of the QRS complex in leads I and II. All of the animals had a sinus rhythm. Heart rates ranged from 60-180 beats per minute, with a mean +/- SD of 104.8 +/- 44.1. The electrical axis was 100 degrees-220 degrees, with a mean +/- SD of 169.5 degrees +/- 40.8 degrees. The base-apex lead provided the most uniform ECG patterns and higher mean amplitudes than did standard leads.     

Influence of 2nd-degree AV blocks,ECG recording length,and recording time on heart rate variability analyses in horses

Objectives

To assess the influence of 2nd-degree AV blocks (AVB) on RR interval-based heart rate variability (HRV) variables; to investigate the effect of using PP interval time series and of artifact filtering on HRV analyses; to investigate the influence of electrocardiogram (ECG) recording length and time of recording; and to calculate day-to-day variability and reference intervals of HRV variables.

Echocardiographic and electrocardiographic examination of clinically healthy, conscious ferrets

Objectives : To assess the feasibility of performing electrocardiography (ECG) and echocardiography on conscious ferrets and to establish reference values for this species under these conditions. Methods : End‐systolic and end‐diastolic left ventricular (LV) diameters, LV and interventricular septal thicknesses were measured by M‐mode echocardiography, while left atrial, aortic and pulmonary trunk diameters were determined by two‐dimensional echocardiography in 46 ferrets. In some animals the maximum velocities of blood flow in the aorta and the pulmonary trunk were also measured by spectral Doppler. ECG examinations were performed by using limb leads both in right lateral recumbency and in the so‐called “hanging” position. In the course of the ECG examinations (n=43), the occurrences, directions, durations and amplitudes of the P, QRS and T waves and the duration of the PR‐ and QT intervals were recorded for all six leads. Results : ECG and echocardiography were successfully performed on non‐sedated ferrets in 90 and 96% of the cases, respectively. Males were significantly heavier and had larger cardiac dimensions compared to females. Clinical Significance : Performance of both echocardiography and ECG are feasible techniques in conscious ferrets, and reference values are now available for future comparisons.     

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.     

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.     

Comparison of heart rate and heart rate variability obtained by heart rate monitors and simultaneously recorded electrocardiogram signals in nonexercising horses

Heart rate (HR) and heart rate variability (HRV) are often determined with Polar heart rate monitors (HRMs; S810i; Polar, Kempele, Finland). The aims of this study were to compare data from horses obtained by Polar HRMs and a portable Televet electrocardiogram (ECG; 100 version 4.2.3; Kruuse, Marslev, Denmark) device and to determine appropriate recording times in horses (n = 14). Correlations were calculated and a Bland-Altman analysis was carried out to examine agreement between recording systems. For beat-to-beat (RR) interval, uncorrected and corrected data were highly correlated irrespective of the recording system and recording time (r > 0.99, P < 0.001). For HRV variables, standard deviation of RR interval and root mean square of successive RR intervals, correlations higher than 0.9 were obtained between uncorrected and corrected ECG but not Polar data. The RR interval, HR, and HRV from corrected Televet and Polar data at no time differed between the recording systems. However, with the increase in recording time, the RR interval decreased (P < 0.001). Thus, for comparisons, recording intervals of similar length should be chosen. Correlations among RR interval, HR, and HRV variables obtained by ECG and HRMs were highly significant at all recording times (r > 0.9, P < 0.001). Correlations increased with increasing recording time. Bland-Altman graphs showed a strong agreement between HRMs and ECG and mean RR intervals, HR, and HRV variables were close to identical. In conclusion, Polar HRMs are as adequate as ECG recordings in horses. Owing to a low HR in stationary horses, recording times below 2 minutes will underestimate changes in HR and HRV.     

Effect of acute haemorrhage on QRS amplitude of the lead II canine electrocardiogram

OBJECTIVE: To examine the effect of acute haemorrhage on the QRS amplitude of the canine lead II surface electrocardiograph (ECG). DESIGN: Ten adult racing Greyhounds were tranquilised, anaesthetised, positioned in right lateral recumbency and connected to recording electrodes of an ECG unit. Baseline six-lead ECG traces were recorded, and further traces were obtained after one unit (460 mL) of blood, and then a second unit, were collected from the femoral artery. RESULTS: There was a consistent and progressive reduction in amplitude of the QRS complex in all leads during acute haemorrhage. QRS amplitude in lead II after removal of two units of blood averaged 74% of the baseline voltage, with individual values of 61 to 91% (P < 0.0001). There were even greater reductions in QRS amplitudes in lead aVL during haemorrhage. In three additional dogs, reductions in QRS voltages were shown to be accompanied by reductions in end-diastolic left ventricular internal dimensions measured echocardiographically. Furthermore, the effects of haemorrhage on the QRS amplitude and echocardiographic measurements were reversed when circulating blood volume was restored by re-infusion of blood removed previously. CONCLUSION: Acute haemorrhage corresponding to an approximately one-third reduction in blood volume caused a substantial reduction in QRS voltage of the surface ECG. It is postulated that this resulted from diminished ventricular distension as a consequence of reduced venous return. A similar mechanism may account for the small-amplitude ECG complexes associated with pericardial effusion, severe dehydration and hypovolaemia.     

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.     

Validation of a digital audio recording method for the objective assessment of cough in the horse

Aim

To validate the use of digital audio recording and analysis for quantification of coughing in horses.

Materials and methods

Part A: Nine simultaneous digital audio and video recordings were collected individually from seven stabled horses over a 1 h period using a digital audio recorder attached to the halter. Audio files were analysed using audio analysis software. Video and audio recordings were analysed for cough count and timing by two blinded operators on two occasions using a randomised study design for determination of intra-operator and inter-operator agreement. Part B: Seventy-eight hours of audio recordings obtained from nine horses were analysed once by two blinded operators to assess inter-operator repeatability on a larger sample.

Results and conclusions

Part A: There was complete agreement between audio and video analyses and inter- and intra-operator analyses. Part B: There was >97% agreement between operators on number and timing of 727 coughs recorded over 78 h. The results of this study suggest that the cough monitor methodology used has excellent sensitivity and specificity for the objective assessment of cough in horses and intra- and inter-operator variability of recorded coughs is minimal.     

Core decompression of the equine navicular bone: an in vivo study in healthy horses

Objective: To determine the physiologic response of the equine navicular bone to core decompression surgery in healthy horses. Study Design: Experimental in vivo study. Materials: Healthy adult horses (n=6). Methods: Core decompression was completed by creating three 2.5‐mm‐diameter drill channels into the navicular bone under arthroscopic control. The venous (P_V), arterial (P_A), articular (P_DIPJ), and intraosseous pressures (IOP) were recorded before and after decompression drilling. Each IOP measurement consisted of a baseline (IOP_B) and a stress test (intramedullary injection of saline solution, IOP_S) recording. Lameness was assessed subjectively and using force plate gait analysis. Fluorochrome bone labeling was performed. Horses were euthanatized at 12 weeks. Navicular bone mineral density (BMD) was measured, and bone histology evaluated. Results: Peak IOP (IOP_max) after stress testing was significantly (P<.05) reduced immediately after core decompression; however, the magnitude of these effects was decreased at 3 and 6 weeks after decompression. A significant (P<.05) correlation existed between IOP_max and BMD. No lameness was observed beyond the first week after surgery. Substantial remodeling and neovascularization was evident adjacent the surgery sites. Conclusion: Navicular bone core decompression surgery reduced IOP_max, and, with the exception of a mild short‐lived lameness, caused no other adverse effects in healthy horses during the 12‐week study period.     

Determination of oral dosage and pharmacokinetic analysis of flecainide in horses.

To determine oral dosage and to evaluate the pharmacokinetics in horses of orally administered flecainide, an antiarrhythmic drug, the correlations between its plasma concentration and PR, QRS and QT intervals in equine electrocardiograms (ECG) were investigated. Six healthy horses were administered a randomly ordered dose of 4 or 6 mg/kg of flecainide acetate. The ECG was monitored (heart rate (HR), PR, QRS, and QT intervals) and blood was taken at timed intervals to measure the plasma flecainide concentrations pre- and post-administration. The maximum plasma concentration reached 1014+/-285 (SD) ng/m/ in 45+/-13 min and 1301+/-400 ng/ m/l in 60+/-37 min for doses of 4 and 6 mg/kg flecainide, respectively. From the pharmacokinetic analysis, clearance rates were 14.6+/-6.4 and 11.7+/-5.2 ml/kg/min and terminal elimination half-lives were 228+/-53 and 304+/-87 min. The QRS and QT intervals increased significantly for both doses following administration, though HR and PR intervals did not change. Plasma flecainide concentrations were significantly correlated with QRS (r=0.935, P<0.001) and QT intervals (r=0.753, P<0.001). In conclusion, plasma concentrations of flecainide for treating equine atrial fibrillation were obtained by oral administration of 4 and 6 mg/kg, and the drug was rapidly eliminated from plasma in horses.     

Putative intestinal hyperammonaemia in horses: 36 cases

Reasons for performing the study: Intestinal hyperammonaemia (HA) has been infrequently reported in individual horses; however, there have been no studies describing clinical and laboratory data as well as short‐ and long‐term outcome in a larger number of cases. Objectives: To describe clinical and laboratory data and short‐ and long‐term outcome in a large group of horses with intestinal HA. Methods: Multi‐centred, retrospective study; case records of horses with HA were reviewed and any horse with a clinical or post mortem diagnosis of intestinal HA was included. Hyperammonaemia was defined as a blood ammonium (NH₄⁺) concentration ≥60 µmol/l and horses with a diagnosis of primary hepatic disease were excluded. Relevant data were recorded and, if appropriate, data from survivors were compared to nonsurvivors to identify potential prognostic indicators. Results: Thirty‐six cases, 26 mature horses and 10 foals with intestinal HA were identified. Case histories included diarrhoea, colic and neurological signs and the most common clinical diagnosis was colitis and/or enteritis. The most common clinical and laboratory abnormalities included tachycardia, increased packed cell volume, hyperlactataemia and hyperglycaemia. Fourteen horses (39%) survived to discharge; NH₄⁺ concentration on admission was the only parameter significantly associated with survival. All surviving horses and foals for which follow‐up information was available recovered completely and returned to their intended use without further complications. Conclusions and potential relevance: Intestinal HA occurs in mature horses and foals and can be associated with severe clinical and laboratory abnormalities; further studies are required to investigate predisposing factors and delineate possible differences in aetiologies.