Abdominal Ultrasonography in Domestic Species

This study was designed to evaluate the use of abdominal ultrasonography in small animals and horses presented at Glasgow University Veterinary School for investigation of abdominal disease and to assess the application of ultrasonography in ovine, canine and feline pregnancy. Initially, the normal ultrasonographic appearance of the liver and spleen were determined by examination of four dogs, six horses and two cats. The appearance of these organs was found to be consistent within and across the species. The most suitable anatomical sites from which these structures could be imaged in these species and the most appropriate equipment were also determined in this study. Twenty-seven dogs and three cats were selected for hepatic ultrasonography and the clinical, radiographic and laboratory indications for the procedure were considered. In twelve out of the thirteen cases of confirmed hepatic disease ultrasonographic abnormalities were detected and these were subsequently compared with the findings at postmortem examination or exploratory laparotomy in the majority of the cases. Twenty dogs and one horse were selected for splenic ultrasonography and in four of these abnormalities were detected. The indications and final diagnoses were reviewed to evaluate the merits and limitations of this procedure. An experiment was designed to determine the accuracy of ultrasonographic estimation of ovine foetal number and to compare the results of inexperienced and experienced operators at various stages of gestation. The optimum efficiency was obtained by ultrasonographic examination at, or around, day 60 of gestation and considerable improvement was observed during the training period of the inexperienced operator. The efficiency of ultrasonographic determination of pregnancy and estimation of foetal numbers in bitches and queens was evaluated by examination of thirty-six bitches and four cats referred to this hospital. Sensitivity of pregnancy diagnosis was 100% but the sensitivity of estimation of foetal number was found to vary with the stage of gestation and the litter size. The most sensitive estimations were obtained in medium sized litters (four to eight foetuses) at days 37 to 43 of gestation. Two methods of estimation of ovine foetal age were developed which were based on ultrasonographic measurement of biparietal and transthoracic diameters, but the estimated age range obtained with these methods was wide. Nine dogs were selected for prostatic ultrasonography. In all of these cases there were clinical signs referrable to the prostate and prostatic disease was subsequently confirmed. Ultrasonographic abnormalities were detected in all of these cases

Non-Invasive Methods for the Investigation of Soft Tissue Injury in the Equine Limb: Diagnostic Ultrasonography and Microwave Thermography, Volume One

A technique was established for the examination of the soft tissue structures of the palmar aspect of the distal equine limb using an ultrasonographic unit equipped with a 7.5 MHz linear array transducer and a separate echolucent stand-off block by performing examinations in six cadaver limbs and in twenty-five adult Thoroughbred horses. The flexor tendons had shapes on ultrasonograms which corresponded with their expected anatomy and their size varied along their length. The lateral to medial and dorsal to palmar dimensions of the flexor tendon were correlated with each other and with the age, weight and height of the horse, the limb circumference and metacarpal bone diameter but consistent relationships between pairs of variables were not evident although the correlation between a variety of individual pairs was significant (p< 0.05)

Cardiac electrophysiological adaptations in the equine athlete-Restitution analysis of electrocardiographic features.

Exercising horses uniquely accommodate 7-8-fold increases in heart rate (HR). The present experiments for the first time analysed the related adaptations in action potential (AP) restitution properties recorded by in vivo telemetric electrocardiography from Thoroughbred horses. The horses were subjected to a period of acceleration from walk to canter. The QRS durations, and QT and TQ intervals yielded AP conduction velocities, AP durations (APDs) and diastolic intervals respectively. From these, indices of active, λ = QT/(QRS duration), and resting, λ0 = TQ/(QRS duration), AP wavelengths were calculated. Critical values of QT and TQ intervals, and of λ and λ0 at which plots of these respective pairs of functions showed unity slope, were obtained. These were reduced by 38.9±2.7% and 86.2±1.8%, and 34.1±3.3% and 85.9±1.2%, relative to their resting values respectively. The changes in λ were attributable to falls in QT interval rather than QRS duration. These findings both suggested large differences between the corresponding critical (129.1±10.8 or 117.4±5.6 bpm respectively) and baseline HRs (32.9±2.1 (n = 7) bpm). These restitution analyses thus separately identified concordant parameters whose adaptations ensure the wide range of HRs over which electrophysiological activation takes place in an absence of heart block or arrhythmias in equine hearts. Since the horse is amenable to this in vivo electrophysiological analysis and displays a unique wide range of heart rates, it could be a novel cardiac electrophysiology animal model for the study of sudden cardiac death in human athletes

The complexity of clinically-normal sinus-rhythm ECGs is decreased in equine athletes with a diagnosis of paroxysmal atrial fibrillation

Abstract: Equine athletes have a pattern of exercise which is analogous to human athletes and the cardiovascular risks in both species are similar. Both species have a propensity for atrial fibrillation (AF), which is challenging to detect by ECG analysis when in paroxysmal form. We hypothesised that the proarrhythmic background present between fibrillation episodes in paroxysmal AF (PAF) might be detectable by complexity analysis of apparently normal sinus-rhythm ECGs. In this retrospective study ECG recordings were obtained during routine clinical work from 82 healthy horses and from 10 horses with a diagnosis of PAF. Artefact-free 60-second strips of normal sinus-rhythm ECGs were converted to binary strings using threshold crossing, beat detection and a novel feature detection parsing algorithm. Complexity of the resulting binary strings was calculated using Lempel-Ziv (‘76 & ‘78) and Titchener complexity estimators. Dependence of Lempel-Ziv ‘76 and Titchener T-complexity on the heart rate in ECG strips obtained at low heart rates (25–60 bpm) and processed by the feature detection method was found to be significantly different in control animals and those diagnosed with PAF. This allows identification of horses with PAF from sinus-rhythm ECGs with high accuracy

The application of Lempel-Ziv and Titchener complexity analysis for equine telemetric electrocardiographic recordings.

The analysis of equine electrocardiographic (ECG) recordings is complicated by the absence of agreed abnormality classification criteria. We explore the applicability of several complexity analysis methods for characterization of non-linear aspects of electrocardiographic recordings. We here show that complexity estimates provided by Lempel-Ziv '76, Titchener's T-complexity and Lempel-Ziv '78 analysis of ECG recordings of healthy Thoroughbred horses are highly dependent on the duration of analysed ECG fragments and the heart rate. The results provide a methodological basis and a feasible reference point for the complexity analysis of equine telemetric ECG recordings that might be applied to automate detection of equine arrhythmias in equine clinical practice.Funded by PetPlan Charitable Trust, grant S17-447-48

Atrial fibrillatory rate as predictor of recurrence of atrial fibrillation in horses treated medically or with electrical cardioversion

Background The recurrence rate of atrial fibrillation (AF) in horses after cardioversion to sinus rhythm (SR) is relatively high. Atrial fibrillatory rate (AFR) derived from surface ECG is considered a biomarker for electrical remodelling and could potentially be used for the prediction of successful AF cardioversion and AF recurrence. Objectives Evaluate if AFR was associated with successful treatment and could predict AF recurrence in horses. Study design Retrospective multicentre study. Methods Electrocardiograms (ECG) from horses with persistent AF admitted for cardioversion with either medical treatment (quinidine) or transvenous electrical cardioversion (TVEC) were included. Bipolar surface ECG recordings were analysed by spatiotemporal cancellation of QRST complexes and calculation of AFR from the remaining atrial signal. Kaplan-Meier survival curve and Cox regression analyses were performed to assess the relationship between AFR and the risk of AF recurrence. Results Of the 195 horses included, 74 received quinidine treatment and 121 were treated with TVEC. Ten horses did not cardiovert to SR after quinidine treatment and AFR was higher in these, compared with the horses that successfully cardioverted to SR (median [interquartile range]), (383 [367-422] vs 351 [332-389] fibrillations per minute (fpm), P < .01). Within the first 180 days following AF cardioversion, 12% of the quinidine and 34% of TVEC horses had AF recurrence. For the horses successfully cardioverted with TVEC, AFR above 380 fpm was significantly associated with AF recurrence (hazard ratio = 2.4, 95% confidence interval 1.2-4.8, P = .01). Main limitations The treatment groups were different and not randomly allocated, therefore the two treatments cannot be compared. Medical records and the follow-up strategy varied between the centres. Conclusions High AFR is associated with failure of quinidine cardioversion and AF recurrence after successful TVEC. As a noninvasive marker that can be retrieved from surface ECG, AFR can be clinically useful in predicting the probability of responding to quinidine treatment as well as maintaining SR after electrical cardioversion