An Exploratory Study on Vectorcardiographic Identification of the Site of Origin of Focally Induced Premature Depolarizations in Horses, Part I: The Atria

Feasibility of transthoracic echocardiographic guidance for multicatheter electrophysiological mapping studies in horses

BACKGROUND

Improved characterization of arrhythmias is based on minimally invasive catheterizations. However, these catheterizations have been poorly explored in horses because apart from 3-dimensional (3D) mapping systems, continuous guidance of the catheter's position with adequate detail is difficult using current imaging modalities.

HYPOTHESIS

Position multiple electrophysiology catheters simultaneously at predetermined strategical positions in the heart using transthoracic echocardiographic guidance.

ANIMALS

Eight adult healthy horses.

METHODS

Observational study. Two electrophysiological studies were performed: 1 procedure with catheters positioned in the right heart in the standing sedated horse and 1 procedure under general anesthesia with catheters positioned in the left heart. Except for the coronary sinus catheter, each catheter positioning was simultaneously guided by right-parasternal transthoracic echocardiography and 3D electro-anatomical mapping.

RESULTS

For each catheter position, a central imaging plane was taken as the starting point, after which the imaging probe was shifted, rotated, and angulated to visualize the catheter over its entire length, including its distal electrode. Catheter positionings in the right heart and left ventricle were successfully guided in the majority of the horses whereas catheter positionings in the left atrium, and especially the pulmonary veins, were challenging to guide echocardiographically.

CONCLUSIONS AND CLINICAL IMPORTANCE

Ultrasound guidance of catheters to specific positions useful for electrophysiological mapping was feasible in the right heart and left ventricle but challenging for the left atrium. This approach creates a perspective for minimally invasive arrhythmia diagnosis without the need for a 3D mapping system. Left parasternal views and intracardiac echocardiography might provide better guidance for left atrial positions.

Einthoven's triangle adapted for horses: Proposal for the Delta configuration

BACKGROUND

Reliable ECGs are crucial for diagnosing arrhythmias, yet a lack of standardization impedes arrhythmia diagnosis and treatment in horses.

OBJECTIVES

To objectively determine an optimal position of Einthoven's triangle for ECG recordings in horses at rest, which can form the basis for standardized ECG recording and improve diagnosis and treatment of arrhythmias.

ANIMALS

The study involved 72 healthy, warmblood horses aged between 3 and 20 years.

METHODS

In view of future 12-lead studies and vectorcardiography, requiring an orthogonal system, Einthoven's triangle was positioned around the heart, in the transverse plane. Therefore, 11 electrodes were placed encircling the thorax behind the olecranon, to construct triangles with a horizontal base. Electrocardiogram recordings from different triangles were analyzed. Signal processing involved filtering, R peak detection, and median complex generation. Principal component analysis (PCA) and Euclidean distance measures were employed for data analysis.

RESULTS

The left mid-thoracic and ventral regions had high PCA scores, indicating high information content. Base-down triangles exhibited higher summed Euclidean distances, contributing to enhanced diagnostic capabilities. A base-down triangle, called "Delta (Δ) configuration" emerged as most informative, while meeting all criteria.

CONCLUSIONS AND CLINICAL IMPORTANCE

The base-down "Delta configuration" is the optimal Einthoven's triangle adapted for horses, providing large amplitudes and potential to provide basic insights into the mechanisms and origins of cardiac arrhythmias. Because the Delta configuration is positioned in the transverse plane, it forms the ideal basis for 12-lead ECG recordings that provide vectorcardiograms in an orthogonal coordinate system. Standardizing electrode positioning could improve ECG data comparability in equine cardiology.

Three-dimensional electro-anatomical mapping and radiofrequency ablation as a novel treatment for atrioventricular accessory pathway in a horse: A case report

We describe the diagnosis and treatment of an atrioventricular accessory pathway (AP) in a horse using 3-dimensional electro-anatomical mapping (3D EAM) and radiofrequency catheter ablation (RFCA). During routine evaluation of the horse, intermittent ventricular pre-excitation was identified on the ECG, characterized by a short PQ interval and abnormal QRS morphology. A right cranial location of the AP was suspected from the 12-lead ECG and vectorcardiography. After precise localization of the AP using 3D EAM, ablation was performed and AP conduction was eliminated. Immediately after recovery from anesthesia an occasional pre-excited complex still was observed, but a 24-hour ECG and an ECG during exercise 1 and 6 weeks after the procedure showed complete disappearance of pre-excitation. This case shows the feasibility of 3D EAM and RFCA to identify and treat an AP in horses.

Electrocardiographic Changes in a Horse with Induced Myocardial Infarction

Simple Summary

During acute myocardial infarction (AMI), the electrophysiological changes are clearly visible on the 12-lead electrocardiogram (ECG), and are as such, an important diagnostic tool in human cardiology. Similar to humans, changes are seen on the ECG in both pigs and dogs, but so far, this has not been studied in horses, despite equine cardiology being a growing field. This study aimed to investigate the ECG changes seen with a 12-lead ECG in a horse with induced myocardial infarction. The ECG changes observed in this case report were comparable to other species with AMI and showed similar patterns throughout the different phases of occlusion. The results could, therefore, indicate that a 12-lead ECG can be used to detect signs of ischemic heart disease, such as AMI, in horses, while they also potentially elucidate certain translational connections between human and veterinary medicine.

Abstract

During acute myocardial infarction (AMI), the ischemia and necrosis of the infarcted tissue result in local electrophysiological changes, which bring about deviations of the ST segment and T wave. In this case report, the aim was to investigate whether these changes could be detected with a 12-lead electrocardiogram (ECG) during acute occlusion of the coronary artery in a 15-year-old Standardbred mare (scheduled for euthanasia due to non-cardiac health problems). The left anterior descending (LAD) coronary artery was occluded using an angioplasty balloon catheter guided through the carotid artery. Two coronary occlusions of 30 min were induced, separated by a 10-min reperfusion phase. AMI led to ST deviations and T-wave amplitude changes (maximum ST deviation was 1.98 mV; T-wave amplitude increased from 6.58 to 9.25 mV). The ST segment almost returned to the baseline during the reperfusion phase. The ECG changes seen after the infarction were comparable to those reported in other species with AMI, suggesting that the 12-lead-ECG can potentially be used to detect signs of myocardial infarction in horses.