Equine 3D electro-anatomical mapping in sinus rhythm elucidates the electrocardiogram and cardiac electrical activation pattern

Understanding the depolarisation pattern of the equine heart under normal physiological conditions, and its relationship to the surface electrocardiogram (ECG), is of uppermost importance before any further research can be done about the pathophysiology of complex arrhythmias. The purpose was to use a 3D electro-anatomical mapping system under general anaesthesia to evaluate the qualitative and quantitative atrial and ventricular depolarisation patterns and correlation with the surface ECG in 7 healthy horses in sinus rhythm. Bipolar activation maps of the endocardium were analysed. The first atrial activation was located at the height of the crista terminalis. Only one interatrial conduction pathway was recognised. The first and second P wave deflections represented the right and left atrial depolarisation, respectively. His bundle electrograms could be recorded in 5 out of 7 horses. Left ventricular activation (Fig. 1 to 3) started at the mid septum, right ventricular activation apically from the supraventricular crest. This was followed by separate depolarisations at the height of the mid free wall. Further ventricular depolarisation occurred in an explosive pattern. Electrically active tissue could be found in all pulmonary veins. In contrast to findings of previous studies, all parts of the ventricular depolarisation contributed to the surface ECG QRS complex. This study provides a reference for the normal sinus impulse endocardial propagation pattern and for conduction velocities in equine atria and ventricles. This information allows to improve ECG reading and develop better recording techniques, such as new 12-lead ECG configurations, in horses

Isolation of pulmonary veins using a thermoreactive implantable device with external energy transfer : evaluation in a porcine model

Background: Pulmonary vein isolation (PVI) is a well-established method for the treatment of symptomatic paroxysmal atrial fibrillation, but is only partly successful with a high rate of electrical reconnection. We introduce a novel technique in which PVI is accomplished by noninvasive heating of a dedicated thermoresponse implant inserted into the pulmonary veins (PV), demonstrated in a porcine model. Methods: A self-expanding nitinol-based implant was positioned in the common inferior PV of 11 pigs, using a fluoroscopy-guided transatrial appendage approach. Ablation was performed through contactless energy transfer from a primary extracorporal coil to a secondary heat ring (HR) embedded in the proximal part of the implant. Electrophysiological conduction was assessed prior to and postablation, and at 3 months. Histological samples were obtained acutely (n=4) and after 3 months (n=7). Results: In total, 13 PV implants were successfully positioned in the inferior PVs of 11 animals. Ablation was performed without injury of adjacent structures. PVI and bidirectional block was electrophysiologically confirmed in all cases immediately at the time of implantation and 3 months later in seven chronic animals in whom testing was repeated. Marked evidence of ablation around the proximal HR was evident at 3 months postprocedure, with scar tissue formation and only mild neointimal proliferation. Conclusions: Successful PVI can be obtained by external electromagnetic heat transfer to a novel pulmonary vein implant

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

Abstract 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

Cartographie électro-anatomique tridimensionnelle et ablation par radiofréquence comme nouveau traitement d'une arythmie provoquée par une voie accessoire chez un cheval

This case report describes the diagnosis and treatment of an atrioventricular accessory pathway (AP) in a horse by three-dimensional electro-anatomical mapping (3D EAM) and radiofrequency catheter ablation (RFCA). During routine check-up of the horse, intermittent ventricular pre-excitation was noticed on the electrocardiogram (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 was still 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

Detection of the origin of atrial tachycardia by 3D electro‐anatomical mapping and treatment by radiofrequency catheter ablation in horses

Abstract Background Atrial tachycardia (AT) can be treated by medical or electrical cardioversion but the recurrence rate is high. Three‐dimensional electro‐anatomical mapping, recently described in horses, might be used to map AT to identify a focal source or reentry mechanism and to guide treatment by radiofrequency ablation. Objectives To describe the feasibility of 3D electro‐anatomical mapping and radiofrequency catheter ablation to characterize and treat sustained AT in horses. Animals Nine horses with sustained AT. Methods Records from horses with sustained AT referred for radiofrequency ablation at Ghent University were reviewed. Results The AT was drug resistant in 4 out of 9 horses. In 8 out of 9 horses, AT originated from a localized macro‐reentrant circuit (n = 5) or a focal source (n = 3) located at the transition between the right atrium and the caudal vena cava. In these 8 horses, local radiofrequency catheter ablation resulted in the termination of AT. At follow‐up, 6 out of 8 horses remained free of recurrence. Conclusions and Clinical Importance Differentiation between focal and macro‐reentrant AT in horses is possible using 3D electro‐anatomical mapping. In this study, the source of right atrial AT in horses was safely treated by radiofrequency catheter ablation

A preclinical study of an implanted device in the pulmonary veins, intended for the treatment of atrial fibrillation in an ovine model

Background: Atrial fibrillation is the most frequent arrhythmia in adults of which the interventional cure is hampered by high recurrence rates. Recurrence after ablation is due to an incomplete isolation of the pulmonary veins. A new ablation technique was performed, in the antra of ovine pulmonary veins, by device implantation, which was heated through a wireless heat-generating system. Methods and Results: Implants were placed transatrially in the pulmonary veins of sheep. Using a wireless heating system, the energy was afterward transferred through wires to the implanted device according to a defined protocol. The position of the implant and the applied lesions were macroscopically evaluated. Samples of the ablated tissue of the atrio-pulmonary vein junction were histologically and immunohistochemically examined. Conclusions: Six ablation procedures in four sheep were successfully performed without adverse cardiac reactions. Implantation of the device and the wireless heat generation was feasible. Sufficient heat was produced at the level of the antra of the pulmonary veins to create ablation lesions, which were histologically and immunohistochemically confirmed

Three dimensional ultra‐high‐density electro‐anatomical cardiac mapping in horses : methodology

Background: Ultra-high-density cardiac mapping allows very accurate characterisation of atrial and ventricular electrophysiology and activation timing. Objective: To describe the technique and evaluate the feasibility of magnetic electroanatomical mapping of the equine heart. Study design: In vivo experimental method development. Methods: A mapping system using an 8.5F bidirectional deflectable catheter with a deployable mini-basket (3–22 mm) containing 64 electrodes divided over eight splines was evaluated. Based upon predefined beat acceptance criteria, the system automatically acquires endocardial electrograms and catheter location information. Electro-anatomical maps were acquired from four horses in sinus rhythm under general anaesthesia. Results: All endocardial areas within each chamber could be reached. Access to the left atrium required the use of a deflectable sheath. With the exception of the left atrial map of horse 1, all four chambers in all four horses could be mapped. Optimisation of the beat acceptance criteria led to a reduction in manual correction of the automatically accepted beats from 13.1% in the first horse to 0.4% of the beats in the last horse. Main limitations: Only a limited number of horses were included in the study. Conclusion: Ultra-high-density 3D electro-anatomical mapping is feasible in adult horses and is a promising tool for electrophysiological research and characterisation of complex arrhythmias