A Labrador retriever with a history of tricuspid dysplasia presented for evaluation of progressive episodic tachycardia. Electrocardiography revealed ventricular pre-excitation during sinus rhythm, which confirmed the presence of an abnormal accessory pathway capable of propagating a global reentrant supraventricular tachycardia (SVT). An Electrophysiological (EP) study defined the SVT mechanism as Orthodromic Atrioventricular Reciprocating Tachycardia (OAVRT) and located the pathway to the right posterior region. Using radiofrequency energy, successful ablation of the accessory pathway was achieved. Six-week follow-up continuous ECG (Holter) monitoring confirmed permanent sinus rhythm with no evidence of tachyarrhythmia or ventricular pre-excitation.