• Arrhythmias;
  • Atrial tachycardia;
  • Cardiology;
  • Dog

Background: Focal atrial tachycardia (FAT) is a common supraventricular tachycardia in dogs.

Objective: To evaluate electrophysiologic characteristics and topographic distribution of FAT.

Animals: Sixteen dogs with symptomatic FAT.

Methods: Retrospective case series. Electrophysiological studies were performed to test the inducibility of documented and no documented arrhythmias. Once induced for each dog, FAT was analyzed for electrogenic mechanism, endocardial electrogram, and location.

Results: Nineteen FATs could be studied in 16 dogs, 12 were automatic, 4 nonautomatic, and 3 incessant. Two dogs had >1 focus. Mean atrial cycle length (CL) was 238.2 ± 69.2 (SD) milliseconds, mean ventricular CL of 292.7 ± 72.5 (SD) milliseconds, with atrioventricular block in 6 cases. Mean presystolic atrial activity recorded at the ectopic focus was –39.9 ± 17.7 (SD) milliseconds. Atrial potentials were fragmented in 11 dogs and were low amplitude in 6 dogs. Sixty-three percent of ectopic foci were distributed within the right atrium (5 crista terminalis, 3 triangle of Koch, 2 tricuspid valve annulus, 1 interatrial septum, and 1 right auricle) and 37% in the pulmonary veins (PVs) (4 right superior PV, 2 left superior PV, and 1 right inferior PV). Persistent atrial fibrillation (AF) and paroxysmal AF were triggered by FATs in 7 dogs (2 with multiple ectopic foci and 4 with at least one PV focus).

Conclusion and Clinical Relevance: According to our findings, dogs have a predominance of right-sided FAT. The majority of FATs are automatic and can trigger AF, particularly in the case of PV location.