Twenty-four hour continuous transvenous temporary right ventricular pacing in healthy horses.

BACKGROUND: The ability to perform transvenous temporary cardiac pacing (TV-TP) is critical to stabilize horses with symptomatic bradyarrhythmias. Reports of successful TV-TP in horses are limited, and only briefly describe short-term pacing. OBJECTIVE: To describe temporary, medium-term (24 h) transvenous right ventricular pacing in awake horses using a bipolar torque-directed pacing catheter. ANIMALS: Six healthy adult institutional teaching horses. METHODS: Prospective experimental study with 2 immediately successive TV-TP lead placements in each horse with a target location of the RV apex. One placement was performed primarily with echocardiographic guidance and 1 primarily with fluoroscopic guidance. In all placements, corresponding images were obtained with both imaging modalities. Horses were then paced for 24 h, unrestricted in a stall with continuous telemetric ECG monitoring. Echocardiographically determined lead position, episodes of pacing failure in the preceding 6 h, and pacing thresholds were recorded every 6 h. Pacing failure was defined as a period of loss of capture longer than 20 s. RESULTS: Pacing leads were placed with both guidance methods and maintained for 24 h with no complications. Two horses with leads angled caudally in the right ventricular apex had no pacing failure, the remaining 4 horses had varying degrees of loss of capture. Leads located in the right ventricular apex had longer time to pacing failure and lower capture thresholds P < 0.05. CONCLUSIONS AND CLINICAL IMPORTANCE: Medium-term TV-TP is feasible and has potential for stabilization of horses with symptomatic bradyarrhythmias. Lead position in the right ventricular apex appears optimal. Continuous ECG monitoring is recommended to detect pacing failure.

Evaluation of a Self-Driven Large Animal Point of Care Ultrasound Learning Program for Veterinary Students.

Point of care ultrasound (POCUS) has the potential to improve healthcare outcomes and is increasingly used in veterinary primary care and specialty practice. The aim of this study was to evaluate a self-driven POCUS learning program during clinical rotations in a large animal teaching hospital. A randomized controlled trial of 94 students evaluated the hypotheses that access to a self-driven POCUS program would improve scores on a written test and the quality of subjective, objective, assessment and plan (SOAP) documents. Use of the POCUS devices and perceptions of veterinary students towards POCUS were analyzed. The self-driven POCUS learning program was feasible, and the perception of most students (94%) was that the program was useful for their education. Access to equipment, ability to scan individually, the hands-on learning aspect, and clinicians' help were the most valued aspects of the program. Earlier access to POCUS in the curriculum, hands-on tutorials/labs, and a more structured learning program were identified by students as aspects to improve. Access to the self-driven POCUS program resulted in significantly higher scores on the written test in a subpopulation of students with lower scores. No significant differences in results on the multiple-choice tests in the subpopulation with higher scores or in SOAP scores of the complete group or subpopulations were found. A self-driven POCUS learning program was perceived as beneficial by students, increased POCUS knowledge in students with lower test scores, and was possible to implement in a busy large animal teaching hospital.

Phlegmonous gastritis in 2 yearling horses.

Phlegmonous gastritis was diagnosed in 2 yearling fillies that were presented with a 1-wk history of fever, lethargy, and hypoproteinemia, associated with a previous diagnosis of equine proliferative enteropathy based on clinical signs and PCR assay detection of Lawsonia intracellularis in fecal samples. Abdominal ultrasound revealed enlargement of the stomach and expansion of its submucosal layer with hypoechoic fluid, as well as thickened hypomotile small intestinal segments. Given the poor prognosis and poor response to treatment, both horses were euthanized, one on the day of presentation and the other after 3 wk of intensive medical management including a combination of antimicrobials, analgesics, and intravenous colloids. At autopsy, acute mural gastritis characterized by severe submucosal edema with suppurative inflammation (i.e., phlegmonous gastritis) and necroulcerative enteritis compatible with the necrotizing form of equine proliferative enteropathy were identified in both horses. The gastric inflammation was associated with thrombosis and mixed bacterial populations, including Clostridium perfringens, that were confined to the submucosa without evidence of mucosal involvement; toxin genes compatible with C. perfringens type C were identified in one case. Human phlegmonous gastritis is an uncommon, often-fatal pyogenic infection that is often associated with mucosal injury, bacteremia, or immunocompromise. Our finding of this unusual gastric lesion in 2 horses with similar signalment, clinical disease, and spectrum of postmortem lesions suggests a similar etiopathogenesis that possibly involves local, regional, or distant hematogenous origin, and should be considered a potential complication of gastrointestinal mucosal compromise in horses.

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.

Pocket-Sized Ultrasound Versus Traditional Ultrasound Images in Equine Imaging: A Pictorial Essay.

This pictorial essay aims to display the image quality of pocket-sized ultrasound devices and hospital-based equipment to provide clinicians visual information about the potential uses of point-of-care ultrasonography (POCUS) in equine practice. Twenty-two paired images were obtained using traditional ultrasound equipment and pocket-sized ultrasound devices from patients evaluated at veterinary teaching hospitals. Images of many common ultrasound windows and miscellaneous sonographic abnormalities were obtained using pocket-sized ultrasound equipment.

Evaluation of Autologous Protein Solution Injection for Treatment of Superficial Digital Flexor Tendonitis in an Equine Model.

Autologous protein solution (APS) has been used anecdotally for intralesional treatment of tendon and ligament injuries, however, its use in these injuries has never been studied in vivo. Our objective was to evaluate the effect of APS on tendon healing in an equine superficial digital flexor (SDF) tendonitis model. We hypothesized intralesional injection of APS would result in superior structural and biomechanical healing. SDF tendonitis was induced in both forelimbs of eight horses using collagenase injection. One forelimb was randomly assigned to receive an intralesional injection of APS, while the other was injected with saline. Ultrasonographic examinations were performed at weeks -1, 0, 2, 4, 8, and 12 following treatment. At 12 weeks, horses were euthanized and SDF samples harvested. Histologic evaluation, biomechanical testing, gene expression analysis, total glycosaminoglycan (GAG) and total DNA quantification were performed. Collagen type III (COL3A1) expression was significantly higher (p = 0.028) in saline treated tendon than in normal tendon. Otherwise, there were no significant differences in gene expression. There were no significant differences in histologic or ultrasonographic scores between groups. Mean total DNA content was significantly higher (p = 0.024) in saline treated tendons than normal tendons, whereas total DNA content was not significantly different between APS treated tendon and normal tendon. Elastic modulus was higher in APS treated than saline treated tendon, but the difference was not significant. Reduced expression of COL3A1 in APS treated tendon may indicate superior healing. Increased total DNA content in saline treated tendon may indicate ongoing healing processes, vs. APS treated tendons which may be in the later stages of healing. Limitations include a relatively short study period and inconsistency in size and severity of induced lesions. Intralesional injection of APS resulted in some improvements in healing characteristics.

Utility and accuracy of a smartphone-based electrocardiogram device as compared to a standard base-apex electrocardiogram in the horse.

OBJECTIVE: Evaluate accuracy and utility of a smartphone-based ECG device compared to a standard base-apex lead ECG in horses. METHODS: ECGs were acquired prospectively from 28 client-owned horses at 2 equine referral hospitals. Twenty-five pairs of 30-s ECG recordings were acquired simultaneously from 23 horses with a smartphone ECG device (a bi-polar single lead recorder coupled to a smartphone with an ECG application) and with a standard base-apex lead ECG; 2 horses provided two pairs of simultaneously acquired ECGs. In one horse, the ECGs pairs were recorded immediately sequentially. An additional 7 smartphone ECGs were recorded from 5 horses without contemporaneous reference ECGs. Three observers independently evaluated all ECGs without knowledge of ECG pairing. Inter- and intra-observer agreement between the 2 ECG modalities was evaluated for rhythm diagnosis and QRS polarity. Heart rate agreement was also evaluated. RESULTS: Intra-observer agreement for rhythm assessment was very high; one observer diagnosed the same cardiac rhythm on both recordings in 24/26 instances and two observers agreed in 25/26 instances. The polarity of the QRS complex was similar on ECGs acquired simultaneously by both systems. Heart rates calculated from ECG pairs were within 1 beat of each other. CONCLUSIONS: The smartphone-acquired ECG accurately identified cardiac rhythm and heart rate in most horses. In one case, small size of the complexes precluded identification of P waves on smartphone-acquired ECGs, resulting in a misdiagnosis. The smartphone-acquired ECG device might allow veterinarians to evaluate and monitor cardiac arrhythmias relatively inexpensively in field or hospital settings.

Assessment of the Cardiovascular System in Horses During Prepurchase and Insurance Examinations.

Arrhythmias detected on prepurchase examination should be confirmed with an ECG. Exercising ECG determines if the arrhythmia is overdriven during exercise or is a safety concern. An echocardiogram is needed in all horses with a grade 3/6 or louder mid to late systolic, holosystolic, or pansystolic murmur or any holodiastolic decrescendo murmur to identify the cardiac abnormality and its hemodynamic impact. Most horses with arrhythmias and murmurs have a normal performance career and life expectancy and are insurable. Risks for sudden death and congestive heart failure associated with the common murmurs and arrhythmias are identified, because these horses cannot be insured.

Evaluation of coagulation and fibrinolysis in horses with atrial fibrillation.

OBJECTIVE: To evaluate horses with atrial fibrillation for hypercoagulability; plasma D-dimer concentrations, as a marker of a procoagulant state; and a relationship between coagulation profile results and duration of atrial fibrillation or presence of structural heart disease. DESIGN: Case-control study. ANIMALS: Plasma samples from 42 horses (25 with atrial fibrillation and 17 without cardiovascular or systemic disease [control group]). PROCEDURES: Results of hematologic tests (ie, plasma fibrinogen and D-dimer concentrations, prothrombin and activated partial thromboplastin times, and antithrombin activity) in horses were recorded to assess coagulation and fibrinolysis. Historical and clinical variables, as associated with a hypercoagulable state in other species, were also recorded. RESULTS: Horses with atrial fibrillation and control horses lacked clinical signs of hypercoagulation or thromboembolism. Compared with control horses, horses with atrial fibrillation had significantly lower antithrombin activity. No significant differences in plasma fibrinogen and D-dimer concentrations and prothrombin and activated partial thromboplastin times existed between horse groups. In horses with atrial fibrillation versus control horses, a significantly larger proportion had an abnormal plasma D-dimer concentration (10/25 vs 2/17), test results indicative of subclinical activated coagulation (18/25 vs 6/17), or abnormal coagulation test results (25/121 vs 7/85), respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Horses with atrial fibrillation did not have clinical evidence of a hypercoagulable state, but a higher proportion of horses with atrial fibrillation, compared with control horses, did have subclinical activated coagulation on the basis of standard coagulation test results.

Cardiac troponin I concentrations in horses with colic.

OBJECTIVE: To determine prevalence of myocardial injury in horses with colic on the basis of high concentrations of cardiac troponin I (cTnI), frequency of cardiac arrhythmias within the first 24 to 48 hours after hospital admission or surgery because of colic, and associations between high cTnI concentrations and cardiac arrhythmias, clinical course, and outcome (survival to discharge from hospital vs nonsurvival [death or euthanasia]). DESIGN: Prospective observational study. ANIMALS: 111 horses with colic. PROCEDURES: Blood was drawn at admission and 12 and 24 hours after admission if horses were treated medically or 12 and 24 hours after surgery if treated surgically. A 24-hour ambulatory ECG was recorded beginning the morning after admission in medically treated cases or after surgery and evaluated for arrhythmias. Clinical and clinicopathologic data and outcome were obtained. Associations between cTnI concentrations and other variables were determined. RESULTS: An abnormal cTnI concentration (≥ 0.10 ng/mL) at admission was significantly associated with the occurrence of ventricular arrhythmias, outcome, and surgical treatment. CONCLUSIONS AND CLINICAL RELEVANCE: The data suggested that horses with colic and high cTnI concentrations at admission were more likely to have ventricular arrhythmias and have a less favorable prognosis for recovery. High cTnI concentrations in horses with colic were suggestive of myocardial damage.

Hypertensive cardiomyopathy in horses: 5 cases (1995-2011).

OBJECTIVE: To describe the prognosis and clinical, echocardiographic, and pathological features of hypertensive cardiomyopathy in horses. DESIGN: Retrospective case series. ANIMALS: 5 horses with cardiac hypertrophy and systemic hypertension. PROCEDURES: Demographics, history, physical and cardiological examination findings, diagnosis, clinical progression, prognosis, and pathological findings were obtained from medical records. RESULTS: The primary diagnosis was chronic laminitis in 3 horses and chronic renal failure in 2. Persistent tachycardia, hypertension, chronic laminitis, or a combination of these prompted the cardiac evaluations. Blood pressure values (median [range]), measured noninvasively, were determined as 190 mm Hg (183 to 261 mm Hg) for systolic pressure, 126 mm Hg (100 to 190 mm Hg) for diastolic pressure, and 155 mm Hg (126 to 222 mm Hg) for mean pressure. No arrhythmias were reported. For the left ventricle, all horses had increased relative wall thickness, mean wall thickness, and ventricular mass. The interventricular septum was thickened at end diastole (n = 5) and in peak systole (4). The left ventricular internal diameter was small at end diastole (n = 4) and in peak systole (3). The left ventricular free wall was thickened at end diastole (n = 3) and in peak systole (4). No associations between blood pressure and variables consistent with hypertrophy were detected. All horses were euthanized because of the grave prognosis of the primary diseases. All 3 horses that underwent postmortem evaluation had cardiovascular abnormalities. CONCLUSIONS AND CLINICAL RELEVANCE: Hypertensive cardiomyopathy should be considered as a comorbid diagnosis in horses with laminitis or chronic renal failure. Information about the development, progression, reversibility, importance of early detection, and long-term sequelae of this condition is needed.

Clinical and diagnostic features of inflammatory airway disease subtypes in horses examined because of poor performance: 98 cases (2004-2010).

OBJECTIVE: To determine whether there are important differences relating to seasonality of signs or clinical features between subtypes of inflammatory airway disease (IAD) in horses caused by neutrophilic and eosinophilic-mastocytic inflammation having dissimilar etiopathologic pathways. DESIGN: Retrospective case series. ANIMALS: 98 horses. PROCEDURES: Data were compiled from medical records of horses examined because of poor performance from 2004 through 2010. Horses underwent a standardized high-speed treadmill test, lameness evaluation, cardiac evaluation, and postexercise bronchoalveolar lavage (BAL). By means of standard BAL cytologic criteria, horses were divided into 4 groups: eosinophilic-mastocytic inflammation, neutrophilia only, mixed inflammation, or no inflammation (control). Associations between IAD subtype and clinical parameters were investigated. RESULTS: Data for 98 horses were obtained, including age, career, season of admission, and results of hematologic evaluation, high-speed treadmill arterial blood gas analysis, upper airway endoscopy, cardiologic evaluation, and BAL. Cytologic evidence of IAD was found in 81% (79/98) of the horses, and 30% (30/98) had erythrocytes present in the BAL fluid after exercise. Horses in the eosinophilic-mastocytic inflammation and mixed-inflammation groups were significantly more likely to be Thoroughbred than Standardbred and have larger amounts of mucus in their BAL fluid. No significant differences were found in season of evaluation, results of exercising blood gas analyses, or comorbidities. CONCLUSIONS AND CLINICAL RELEVANCE: No association between season and cytologic profile of BAL fluid and no major effects of IAD subtype on pulmonary gas exchange during exercise were seen in this population of horses.

Chronic oral therapy with enalapril in normal ponies.

Enalapril is an angiotensin converting enzyme (ACE) inhibitor that is frequently used in human, feline and canine patients with cardiac disease. Its use has been associated with impotence in human patients. The purpose of this study was to evaluate if enalapril (0.5mg/kg PO, q24h) is likely to alter behavior in stallions and to assess its effect on ACE activity at the standard dose used in dogs and cats. Twelve pony stallions were evaluated by physical examination and echocardiography followed by treatment with enalapril (n=6) or placebo (n=6) for 2 months. After one month, blood was drawn and stored to evaluate ACE activity in the 2 groups. At the end of the study, repeat physical examination and echocardiography were performed. Physical examination, echocardiographic indices, and reproductive performance were unchanged and there was no suppression of ACE activity. Results of this study suggest that enalapril (0.5mg/kg PO, q24h) is either poorly absorbed in the horse or is inadequately converted to the active form of the drug, enalaprilat.

Ultrasonographic appearance of the lower urinary tract in fifteen normal horses.

The purpose of this study was to describe the normal ultrasonographic appearance of the caudal portion of the equine ureters, pelvic urethra, and urinary bladder and to assess ureteral contractility. Fifteen horses with no evidence of urinary tract disease (five females, five intact males and five geldings) were studied. The lower urinary tract was evaluated ultrasonographically using a transrectal approach. The normal ultrasonographic appearance and anatomic location of structures of the lower urinary tract were evaluated and anatomic relationships described. Both ureters were identified dorsal to the bladder and at their openings into the bladder. Their relationship and different appearance from the male deferent ducts/ampullae and vesicular glands was noted. Ultrasonographic measurements of the diameter of the ureters and urethra were obtained and the ureteral, urethral, and urinary bladder wall thickness recorded. The normal parameters established in this study will be useful during sonographic examination of horses with suspected urinary tract disease. Transrectal ultrasonographic examination is valuable in assessing the presence and frequency of ureteral contractions as well as in detecting structural abnormalities of the lower urinary tract. The use of high-frequency transrectal ultrasound transducers allows for excellent visualization of the structures of the equine lower urinary tract.

Septicemia and cardiovascular infections in horses.

This article first reviews cardiovascular infections, including endocarditis, myocarditis, vasculitis, and pericarditis. It then addresses what is known at this stage about the effects of sepsis on the cardiovascular system. Some information is provided from current human literature to familiarize the reader with the diagnostics and therapeutics that may eventually be used in equine practice as well.