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Topic:Cardiac Arrhythmias
Cardiac arrhythmias in horses refer to irregularities in the heart's rhythm, which can affect the efficiency of blood circulation. These arrhythmias can result from various factors, including electrolyte imbalances, structural heart changes, or systemic diseases. Common types of arrhythmias in horses include atrial fibrillation, ventricular tachycardia, and premature ventricular contractions. The presence and type of arrhythmia can influence a horse's performance and overall health. Diagnostic tools such as electrocardiography (ECG) are used to identify and assess these irregular heart rhythms. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, diagnosis, and management of cardiac arrhythmias in equine medicine.
Myocardial dysfunction associated with low-dose endotoxin administration in adult horses. Horses with endotoxemia have variable myocardial function, but little is known about the severity or persistence of myocardial dysfunction (MD). Objective: Horses with experimentally induced endotoxemia have systolic and diastolic MD. Methods: Twelve systemically healthy horses. Methods: Horses were given Escherichia coli lipopolysaccharide 30 ng/kg over 60 min. Echocardiography and cardiac troponin I (cTnI) measurements were performed at baseline, 1, 3, and 5 h post-endotoxin. Fluid therapy (10 L), polymyxin B (6000 IU/kg), and flunixin meglumine (1.1 mg/kg) were administered intravenou...
Electrocardiographic recording in horses at rest: a concordance analysis of two methods. Cardiac arrhythmias are frequently detected during routine auscultation in athletic horses. Assessment of their clinical significance requires electrocardiography (ECG) to analyze waveforms and intervals. In recent years, portable ECG devices have been introduced to simplify electrocardiographic examination, offering advantages such as ease of use and the ability to review results via a smartphone. This study evaluated the utility and accuracy of a portable ECG device compared with a standard electrocardiograph. Simultaneous ECG recordings were obtained from 28 healthy adult horses at rest usi...
Magnesium Dysregulation. Magnesium (Mg) is a critical intracellular cation involved in energy metabolism, neuromuscular and cardiac stability, and endocrine regulation of calcium and potassium. In horses, Mg dysregulation is common in gastrointestinal disease, systemic inflammation and critical illness, yet often remains underdiagnosed. Hypomagnesemia contributes to ileus, cardiac arrhythmias, and refractory hypocalcemia or hypokalemia, whereas hypermagnesemia is rarely reported and typically iatrogenic. This review summarizes Mg physiology, regulation, clinical manifestations of Mg dysregulation, diagnostic approache...
Ostium-specific equine pulmonary vein myocardial sleeve gross anatomy and structural evidence of interatrial myocardial continuity with potential implications for ablation strategies. Pulmonary vein (PV) myocardial sleeves (MSs) harbour an arrhythmogenic substrate for atrial fibrillation. However, equine-specific data on MS distribution and wall thickness are limited yet essential for developing ablation strategies. In humans, posterior interatrial connections can compromise right-sided PV isolation. Objective: To study equine PV MS distribution, quantify ostial/branch diameters, antral lengths, characterise MS distal edge morphology, measure wall thickness and explore an interatrial myocardial continuity between the MSs of caudal branches draining through ostium III (PV II...
Pharmacokinetic/Pharmacodynamic Analysis of Quinidine-Induced Dominant Frequency Reduction in Thoroughbred Horses With Atrial Fibrillation. Quinidine has long been used for the pharmacological treatment of atrial fibrillation (AF) in horses; however, the plasma concentration required for conversion to sinus rhythm remains unclear. Dominant frequency (DF), derived from surface electrocardiograms, reflects atrial activation rate during AF. This study aimed to quantify the relationship between plasma quinidine concentration and DF using a pharmacokinetic/pharmacodynamic (PK/PD) approach. Ten Thoroughbred horses with naturally occurring AF received quinidine sulfate via a nasogastric tube. Plasma quinidine concentrations and DF values...
Cycle length variation assists in differentiation of atrial, ventricular, and sinus arrhythmias in horses at rest. Criteria for arrhythmia classification in horses are insufficient, particularly when differentiating atrial premature complexes (APCs) from sinus arrhythmia (SA). This study investigated RR and PP interval changes between SA, APCs, and ventricular premature complexes (VPCs). Unassigned: 30 resting ECGs were reviewed: 10 each containing SA, APC, and VPC. Sequences of 10 RR and PP intervals were recorded for each arrhythmia (20 events/ECG). Percent RR and PP deviations were calculated (1) between sequential intervals (%ΔSEQPP and %ΔSEQRR, respectively) and (2) compared to averaged baseline int...
Pulsed wave tissue Doppler imaging of the left ventricle in foals: Feasibility, inter- and intra-observer variability and wave pattern over the first days of life. Tissue Doppler imaging (TDI) may improve the assessment of myocardial function in neonatal foals. Objective: To document the feasibility of left ventricular pulsed wave (PW) TDI, inter- and intra-observer variability and wave pattern over the first 5 days of life. Methods: Prospective observational study. Methods: Transthoracic echocardiography was performed in 25 healthy Standardbred foals within the first 24 h after birth (T1), between 60-84 h (T2), and 108-132 h (T3) after birth using right parasternal short-axis (R-LV SAX) and subcostal long-axis views at the mitral annulus, both a...
First experience with radiofrequency catheter ablation in horses with recurrent, persistent naturally occurring atrial fibrillation. Myocardial sleeves in the caudal vena cava and pulmonary veins are a potential trigger for initiation and perpetuation of atrial fibrillation (AF) in horses. Objective: Isolation of myocardial sleeves in the caudal vena cava or pulmonary veins might reduce the risk for AF recurrence. Methods: Case series. Methods: Records from seven horses with persistent, recurrent, naturally-occurring AF that were treated with three-dimensional electro-anatomical mapping and radiofrequency catheter ablation (RFCA) in order to reduce recurrence risk were reviewed. Mapping of the caudal vena cava was performed...
Morphological investigation of myocardial sleeves with potential relevance to atrial fibrillation in Norwegian-Swedish Coldblooded Trotters. Myocardial sleeves (MSs) are thin layers of cardiac muscle that extend from the atria into the caval and pulmonary veins. They are recognised as important structures in both initiating and maintaining atrial tachycardia, and especially atrial fibrillation (AF), which is the most clinically important cardiac arrhythmia in horses with a reported prevalence of 1.3-2% in Standardbred racehorses. In contrast, the Norwegian-Swedish Coldblooded Trotter (NSCT) has a much lower prevalence of AF despite experiencing similar physical demands. The purpose of this study was to describe the macro-, and micr...
Case report: exercise-associated sudden death in a Thoroughbred racehorse with cardiac lesions. Exercise-associated sudden death (EASD), defined as acute collapse and death in an apparently healthy racehorse during or within ~1 h after exercise, is currently among the top concerns in the racing industry. Cases of EASD with no cause of death identified at necropsy are frequently presumed to be of cardiac origin. In such cases, in addition to a regular necropsy, a cardiac examination protocol is performed that includes a detailed gross examination and microscopic evaluation of 11 regions of the heart. Very often this protocol is unrewarding because there are no microscopic lesions to expl...
Using a wearable electrocardiogram (ECG) patch adapted for 7-day monitoring in the horse. Arrhythmias can cause poor performance and sudden death in horses. Long-term (>24 h) electrocardiogram (ECG) monitoring has been used to identify arrhythmias in humans and is superior to short-term monitoring for transient arrhythmia detection. Televet is the current equine gold-standard ECG device. The Cardea SOLO™ (CS) is a single-use monitor with automated ECG analysis software allowing ECG monitoring for 7 days. Objective: Our objective was to validate the performance of the CS compared to the Televet. Methods: Method validation. Methods: ECGs were performed on 12 healthy horses s...
Validation of a smart textile electrocardiographic monitoring device in racehorses during high-speed exercise. Exercise-associated cardiac arrhythmias may contribute to poor performance and sudden cardiac death in horses. Widespread monitoring is limited by device availability and suitability for field use. Objective: To (1) compare electrocardiographic (ECG) quality from a smart textile system (Myant Skiin Equine) with a reference device (Televet II) during exercise, and (2) evaluate whether arrhythmia detection with Myant Skiin Equine is comparable to the Televet II. Methods: Prospective blinded clinical study. Methods: Fifty racehorses (25 Thoroughbreds, 25 Standardbreds) underwent up to three high-...
Signal-averaged electrocardiography in horses: characteristics of ventricular late potentials in healthy Thoroughbreds and horses with cardiac abnormalities. Sudden death in horses, often attributed to lethal arrhythmias, poses significant welfare and economic risks, yet its prediction remains challenging. This study aimed to characterize ventricular micro-potentials using signal-averaged electrocardiography (SAECG) and evaluate their potential for assessing sudden death risk. High-resolution orthogonal X-, Y-, and Z-lead ECGs were recorded in 24 healthy Thoroughbreds (aged 2-31 years), one horse with bupivacaine-induced myocardial injury, and three horses with persistent pathological murmurs. SAECG parameters, including filtered QRS duration (fQRS...
Comparative cardiac histopathology and toxicology screens in horses succumbing to exercise-associated sudden cardiac death and control horses. Horse racing has faced increased scrutiny because of concerns about equine welfare and the safety of both equine and human participants. Sudden death (SD) in racehorses is relatively uncommon, and its causes are still unclear. Little information and considerable confusion exist regarding the clinical significance of microscopic lesions in the hearts of horses with SD. We examined the hearts of 29 horses that suffered exercise-associated sudden cardiac death (EASCD) and 29 clinically healthy control horses that were euthanized because of catastrophic musculoskeletal injuries. Acute cardiomyocyt...
Prevalence of cardiac arrhythmias in poorly performing horses. Electrocardiogram abnormalities are common in racehorses and can affect performance. Unassigned: This study aimed to analyze the results of electrocardiographic problems and measure the frequencies of various cardiac arrhythmias. Unassigned: This cross-sectional study was conducted between September 2023 and August 2024. Standard electrocardiographic recordings were obtained from all horses, and cardiac troponin levels were measured. Out of the 114 poorly performing adult horses, 10 cases without arrhythmia were considered the control group. Seventy-four horses (64.9%) had at least one type of...
Pathology of sudden death in racehorses: a review. Sudden death (SD) is the second most important syndrome associated with death in racehorses. The cause of SD in a large number of horses remains undetermined, and, in many of these cases, causes are not found by gross or microscopic postmortem examinations. Among the known causes of SD are traumatic injuries, including fractures of skull, neck, and pelvis; intoxications (e.g., anticoagulant rodenticides); and others. For many cases of SD in which no significant lesions are found, heart failure, probably associated with arrhythmias, is suspected. Precise phenotypic characterization of SD in hor...
Paroxysmal atrial fibrillation-like bursts in racehorses: do they affect speed and performance? A case control study. Paroxysmal atrial fibrillation (pAF) occurs sporadically in horses and has been implicated in poor performance. Diagnosis in large numbers of horses has previously relied on post-exercise ECGs. Objective: Describe pAF-like bursts detected during exercise and determine their effect on speed, stride, and racing performance. Methods: Retrospective case control study, evaluating records of exercising ECG consultations referred to a specialist practice to identify horses with pAF-like bursts. Controls were selected from the same population as racehorses with normal exercising ECGs. Results: Eleven ...
Delta (Δ) 12-lead electrocardiography and vectorcardiography to identify the origin of focally induced atrial and ventricular premature depolarizations in horses. Cardiac arrhythmias are common in horses, but their clinical and prognostic relevance remains poorly defined. Despite the importance of localization for diagnosis and treatment, noninvasive methods to identify arrhythmogenic foci are limited. Objective: Evaluate the ability of delta (Δ) 3- and 12-lead ECGs and 2-dimensional (2D) and 3-dimensional (3D) vectorcardiography (VCG) to identify the site of origin of focally induced atrial and ventricular premature depolarizations in horses. Methods: Eight healthy horses underwent 2 electrophysiological studies, 1 standing, and 1 under general anesth...
Treatment of ventricular arrhythmias with oral sotalol in four horses. Sustained ventricular arrhythmias (VAs) in horses can require medical intervention. Prompt pharmacological treatment is indicated when the arrhythmia leads to hemodynamic or electrical instability. Established antiarrhythmic treatment of VA in horses includes lidocaine and magnesium, administered parenterally. Other antiarrhythmic agents are used; however, concerns regarding adverse effects, financial restrictions, logistics of administration, and lack of access often limit their use. While anecdotal reports of oral administration of sotalol for treatment of VA in horses exist, sotalol has pri...
Exercising electrocardiograms from Thoroughbred racehorses with exercise associated sudden death. Exercise associated sudden death (EASD), defined as a fatal collapse in a closely monitored and previously presumed clinically healthy horse that occurs during exercise or within approximately 1 h after exercise, is disproportionately more common in equine than in human athletes. Objective: To describe ECGs from EASD cases in Thoroughbred racehorses. Methods: Retrospective case series. Methods: An international call for potential cases was made through direct contact with relevant racing authorities requesting that trainers of horses which had experienced EASD consent to researchers gaining ac...
Behavioral and cardiorespiratory effects of a medetomidine and tramadol combination in horses. The use of combinations of sedative and analgesic drugs during standing procedures in horses is necessary to provide reliable sedation with minimal ataxia and reduced responses to surgical or other stimuli in horses. Objective: This study assessed the behavioral and cardiorespiratory effects of medetomidine (M) administered with and without tramadol (T) in horses. Methods: Eight horses were sedated intravenously with M (5 µg/kg) alone or with T (2 mg/kg) in a arandomized, blind, two-way crossover trial. Behavioral responses, including head height above the ground (HHAG), postural instability ...
Cardiac arrhythmias during intense exercise in Thoroughbred racehorses: frequency and association with subsequent race performance. The frequency, characteristics, and relationship with performance of arrhythmias occurring during high-intensity exercise in Thoroughbred racehorses remain poorly understood. Objective: Describe the frequency, characteristics, and association with subsequent race performance of arrhythmias occurring during intense exercise. Methods: Seventy-one racehorses competing in races sanctioned by the Hong Kong Jockey Club. Methods: Risk-based case-control study. Single-lead ECGs were recorded during high-intensity trials using wearable devices. Ectopic depolarizations identified during warm-up, maximal...
Multicentric Malignant Melanoma in a Grey Mare: A Case Report. Grey coat color in horses, resulting from a 4.6 kb copy number variation (CNV) within the syntaxin 17 (STX17) gene (Grey locus), is linked to progressive hair depigmentation and a markedly increased risk of melanoma, likely to its function as a melanocyte-specific enhancer. Objective: This report details the clinical, pathological, and genomic findings of a 26-year-old flea-bitten grey mare with multiple melanocytic tumors, progressive dyspnea, and congestive heart failure. Due to the poor prognosis the horse was euthanized and submitted for necropsy to the Long Island University - Lewyt Colle...
Detection of exercising ectopic atrial and ventricular beats using non-linear analysis of clinically normal racehorse electrocardiograms at rest or low-intensity exercise. Cardiac arrhythmias are common in healthy athletic horses and may lead to poor athletic performance or exercise-associated sudden death. Early detection of high-risk horses is an important goal of cardiovascular diagnostics. We hypothesised that non-linear analysis of electrocardiogram disorderliness can be used to identify horses exhibiting intermittent ectopic atrial and ventricular heart rhythm abnormalities at exercise using brief, artifact-free recordings of normal sinus rhythm electrocardiograms collected at submaximal heart rates. In a convenience prospective cross-sectional study, ambu...
Cardiac morphologic changes induced by a 10-week water treadmill training for show jumping horses: A preliminary evaluation. This study aimed to investigate cardiac adaptations and energy expenditure of jumping horses after water treadmill (WT) training. Six trained horses were evaluated before (PRETR) and after (TR) a WT training (20 min, twice/week, water at carpus height) for 10 weeks. Transthoracic echocardiography was performed at PRETR and TR with phased array transducer (1.9-4 MHz) to obtain interventricular septal thickness (IVS), LV internal diameter (LVID), and posterior wall thickness (LVPW) at end-diastole (d) and systole (s) and heart rate (HR). Left ventricule end diastolic volume (Vd) and end syst...
QT interval and cardiac restitution dynamics in racehorses: Observations during maximal effort. Sudden cardiac death is a leading cause of athletic death in both humans and horses, making racehorses a potentially valuable model for investigating sudden cardiac death. Cardiac restitution ratio (QT/TQ interval) is used to assess arrhythmia risk in humans, but investigations in athletes are scarce. The objective was to characterize QT interval and cardiac restitution ratio in Thoroughbred racehorses during maximal effort. Automated restitution analysis was performed using 2709 pairs of cardiac cycles from 30 Thoroughbred horses during races. Cardiac cycles were obtained during: pre-race; ac...
Vectorcardiography at rest and during exercise in horses using the Delta (Δ) 12-lead configuration. Twelve-lead electrocardiography (ECG) is essential in human cardiology but remains poorly investigated in equine medicine due to a lack of standardization and inconsistent findings. Objective: Describe the normal vectorcardiogram (VCG) variation in horses at rest and during exercise using Delta 12-lead ECG, including repeatability and intra- and interobserver variations. Methods: One hundred two healthy Warmblood horses, aged 3-20 years, were examined at rest, of which 30 also during exercise. Methods: Prospective, observational study. Electrocardiograms were recorded using a Δ 12-lead confi...
Utility of dynamic preload indices of hypovolemia in isoflurane-anesthetized horses. To evaluate the utility of the dynamic indices, systolic pressure variation (SPV%), pulse pressure variation (PPV%) and plethysmographic variability index (PVI%) during induced hypovolemia, and to determine their correlation with cardiac output (CO) in anesthetized horses. Methods: Prospective experimental study. Methods: A group of eight healthy adult research horses. Methods: After sedation with intravenous (IV) xylazine, anesthesia was induced with IV ketamine and diazepam and maintained with constant-dose isoflurane delivered in 100% oxygen. Horses were positioned in dorsal recumbency, par...
Evaluation of Pulse Pressure as a Hemodynamic Marker of Cardiac Disease in Dogs and Horses Undergoing Pre-Anesthetic Assessment. Pulse pressure (PP) reflects ventricular stroke volume and arterial compliance, but its utility as a marker of cardiac disease in animals is not well established. This study evaluated the association between PP and echocardiographically confirmed cardiac abnormalities in dogs and horses and assessed its potential in pre-anesthetic evaluation. Clinical and echocardiography examination of 20 dogs and 20 horses was sufficient for inter-group comparisons and assignments to a Cardiac group (echocardiographically confirmed cardiac disease) or a Control group (healthy animals). Non-invasive oscillome...
Case Report: Inhaled salbutamol in the successful treatment of life-threatening acute hyperkalaemia in an anaesthetised horse. Hyperkalaemia is an uncommon complication of general anaesthesia in healthy horses. This case report describes the occurrence of life-threatening acute hyperkalaemia in a 13-year-old, female French Trotter anaesthetised for experimental right and left atrial 3D electro-anatomical mapping. Intra-operative development of hyperkalaemia (7.55 mmol/L) (Ref. 3.00-4.00 mmol/L) with atrial standstill on ECG necessitated transvenous ventricular pacing while initial treatment with insulin and glucose was initiated. Plasma potassium levels continued to increase (8.00 mmol/L) prompting adjunctive tr...
