• Arrhythmias;
  • Atrial tachycardia;
  • Atrioventricular tachycardia;
  • ECG;
  • SVT

Background: The 12-lead surface ECG is validated for differentiating supraventricular tachycardias (SVT) in humans. Despite the description of SVT in veterinary medicine, no studies have analyzed the electrocardiographic features of this type of arrhythmias in dogs.

Objective: To describe the specific electrocardiographic criteria used to differentiate the most common SVT in dogs.

Animals: Twenty-three dogs examined at Clinica Veterinaria Malpensa for SVT with the mechanism documented by electrophysiologic studies (EPS).

Methods: Twelve-lead electrocardiographic variables obtained from 14 dogs with orthodromic atrioventricular reciprocating tachycardia (OAVRT) and 9 dogs with focal atrial tachycardia (FAT) were compared.

Results: Dogs with FAT had faster heart rates (278 ± 62 versus 229 ± 42 bpm; P= .049) and less QRS alternans (33 versus 86%; P= .022). P waves appeared during tachycardia in 22 dogs, with a superior axis in 100% of OAVRT and 22% of FAT (P < .001). OAVRT was characterized by a shorter RP interval (85.0 ± 16.8 versus 157.1 ± 37.3 ms; P < .001) and smaller RP/PR ratio (0.60 ± 0.18 versus 1.45 ± 0.52; P < .001). Repolarization anomalies were present in 64% of OAVRT and no FAT (P < .001). Multivariate analysis identified QRS alternans and a positive P wave in aVR during tachycardia as independent predictors of arrhythmia type.

Conclusion and Clinical Importance: Electrocardiographic criteria used in people for differentiating SVT can also be applied in dogs.