Stijn Schauvliege

Background Recently, treatment of equine atrial tachycardia by three‐dimensional electro‐anatomical mapping (3D EAM) and radiofrequency catheter ablation (RFCA) has been described. Myocardial sleeves in the caudal vena cava and pulmonary veins are a potential trigger for initiation and perpetuation of atrial tachycardia and atrial fibrillation in the horse. Isolation of these myocardial sleeves by RFCA may be an effective treatment for these arrhythmias. Objectives To describe the feasibility of 3D EAM and RFCA to isolate caudal vena cava and pulmonary veins in adult horses using 3D mapping and a contact force (CF)‐guided ablation system. Study design In vivo experiments. Methods 3D EAM and RFCA was performed in five horses without cardiovascular disease under general anaesthesia, using the CF‐guided system CARTO®3. Point‐by‐point RFCA aimed for isolation of caudal vena cava and pulmonary veins. Radiofrequency energy was delivered in power‐controlled mode with a target power of 45 W, CF between 10 and 15 g and 30 mL/min irrigation rate, until an ablation‐index of 450–500 was reached. Results In the right atrium, myocardial sleeves of the caudal vena cava were isolated ( n = 5). In the left atrium, isolation of ostium II ( n = 3), ostium III ( n = 1) and ostium I, II and III en bloc ( n = 1) was performed. Successful isolation was confirmed by entrance and exit block. Main limitations Horses were euthanised at the end of the procedure, so long term effects such as potential reconnection of isolated veins could not be studied. Conclusions This is the first description of 3D EAM and RFCA with CARTO®3 in horses, thereby showing the technical feasibility and successful caudal vena cava and pulmonary vein isolation. CF measurement allowed monitoring of catheter‐tissue contact, resulting in efficient acute lesion creation as confirmed by entrance and exit block. This is a promising treatment for cardiac arrhythmias in horses.

Sedative as well as protective effects during hypoxia have been described for gamma‐hydroxybutyric acid (GHB). Six swine ( Sus scrofa domesticus ) of 6 weeks old were administered NaGHB at a dose of 500 mg/kg intravenously (IV) and 500 and 750 mg/kg orally (PO) in a triple cross‐over design. Repeated blood sampling was performed to allow pharmacokinetic analysis of GHB. Whole blood concentration at time point 0 after IV administration was 1727.21 ± 280.73 μg/mL, with a volume of distribution of 339.45 ± 51.41 mL/kg and clearance of 164.94 ± 47.05 mL/(kg h). The mean peak plasma concentrations after PO administration were 326.57 ± 36.70 and 488.01 ± 154.62 μg/mL for 500 mg/kg and 750 mg/kg, respectively. These were recorded at 1.42 ± 0.72 and 1.58 ± 0.58 h after PO dose for GHB 500 mg/kg and 750 mg/kg, respectively. The elimination half‐life for IV and PO 500 mg/kg and PO 750 mg/kg dose was respectively 1.33 ± 0.30, 1.16 ± 0.31 and 1.11 ± 0.33 h. The bioavailability ( F ) for PO administration was 45%. No clinical adverse effects were observed after PO administration. Deep sleep was seen in one animal after IV administration, other animals showed head pressing and ataxia.