Cardiovascular images: long-term electrocardiogram assessment of ventricular modulated parasystole in a 17-month-old dog

A 17-month-old male Staffordshire bull terrier dog was referred in order to assess an asymptomatic arrhythmia. A 5-min electrocardiogram and 24-h Holter monitor recording revealed the following criteria for ventricular parasystole (VP): mathematically related interectopic intervals, varying coupling intervals of ventricular complexes with sinus complexes, and the presence of fusion complexes. The effect of modulation of the VP cycle length by the sinus rhythm was highlighted on the Holter monitor recording. As the dog did not present with clinical signs and the arrhythmia was judged benign, treatment was not prescribed. The veterinary literature about VP is quite poor. A few case reports exist, all without an association with cardiac disease and any evidence of usefulness of an anti-arrhythmic treatment. A long period (more than a short electrocardiogram) is advised in order to definitively diagnose VP and to rule out malignant arrhythmia.