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

Figures

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  FIGURE 1. Comparison of a normal (A) and pre‐excitation (B) complex from a modified base‐apex electrocardiogram taken 5 s apart at a constant heart rate of 40 bpm. The black vertical line indicates the start of the P wave in both complexes. The red area indicates the PQ segment of the normal complex and how it relates to the pre‐excited QRS. (A) For the sinus beat, the PQ segment is 124 ms and QRS duration is 129 ms. (B) During pre‐excitation, the PQ segment is very short and immediately followed by the pre‐excited QRS complex, which is widened (201 ms) and shows a different morphology. A delta wave can be identified as a reduced dV/dt in the initial portion of the widened QRS complex. Comparison of both traces shows that during pre‐excitation, the entire pre‐excited ventricular depolarization is completed before the normal AV conduction reaches the ventricle.

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  FIGURE 2. Modified base‐apex electrocardiogram (ECG) at rest (A), exercise (B), and after pharmacologic testing (C–E). 1 (A) An ECG at a resting heart rate of 44 bpm shows sinus rhythm (first and last complexes) and intermittent pre‐excitation (2rd‐4th complex). The normal complexes have a PQ interval and PQ segment of 230 and 124 ms, respectively, and a normal QRS morphology with a duration of 129 ms. The pre‐excitation complexes show a short PQ interval and PQ segment of 137 and 57 ms, respectively, and an abnormal QRS morphology with a prolonged QRS duration of 201 ms. (B) ECG during recovery after exercise at a heart rate of 88 bpm: there is a gradual transition from normal conduction to conduction along the accessory pathway. This can be observed by the progressive increase of the R wave amplitude and a shortening of the PQ intervals and segments. The pre‐excitation complexes have a PQ interval and PQ segment of 151 and 67 ms, respectively, and a QRS duration of 172 ms. (C) ECG during isoprenaline infusion (0.02 μg/kg/min) at a heart rate of 103 bpm. Isoprenaline induced sinus tachycardia with normal conduction via the AV node. These complexes have a PQ interval and PQ segment of 170…

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  FIGURE 3. (A) Activation map of the right atrium (RA) and right ventricle (RV). Only a small part of the 3D anatomy (gray) has been created and only a few activation points (color) have been registered because the accessory pathway was quickly found. The color varies following the rainbow spectrum from red (earliest activation) to purple (latest activation) in relation to the electrograms from the coronary sinus, which served as a timing reference. The map demonstrates the earliest ventricular activation in continuation with atrial activation, which defines the ventricular insertion of the accessory pathway, located at the right cranial free wall between the right atrium and right ventricle. The dotted line indicates the demarcation between RA and RV. (B) Surface electrocardiogram (yellow traces), electrogram from the coronary sinus (CS) catheter (pink traces), recording from the ablation catheter at the accessory pathway (light blue trace) and unipolar recording from the ablation catheter (white trace), recorded at the same timing and catheter position as Figure 3A. The accessory pathway potential can be recognized as the sharp spike (green arrow) between the atrial (first red arrow) and…