In dogs, the heart’s rhythm is typically initiated by electrical signals originating from the sinoatrial node, a specialized cluster of cells located in the right atrium, which serves as the heart’s natural pacemaker. These signals travel to the ventricles, the lower chambers of the heart, via the atrioventricular (AV) node and the AV bundle. However, in cases of Wolff-Parkinson-White Syndrome (WPW), a condition in which ventricular pre-excitation occurs, impulses from the sinoatrial node or atrium activate a portion of the ventricles prematurely through an additional pathway, bypassing the AV node. This can lead to various symptoms, including an abnormally rapid heart rate known as supraventricular tachycardia. Despite this irregular activation, the remaining ventricular tissue is still activated through the heart’s normal conduction system.
Symptoms and Types
Symptoms of Wolff-Parkinson-White Syndrome in dogs may include fainting (syncope) and an extremely rapid heart rate exceeding 300 beats per minute.
Causes
The causes of Wolff-Parkinson-White Syndrome in dogs can be attributed to congenital or acquired heart defects. Congenital heart disease may involve abnormalities in the heart’s conduction system, such as a hole between the two atria (atrial septal defect) or an improperly developed valve separating the right atrial chamber from the left ventricular chamber (tricuspid valvular dysplasia in dogs). Acquired heart disease, such as hypertrophic cardiomyopathy, though more commonly observed in cats, can also be associated with WPW syndrome.
Diagnosis
To diagnose Wolff-Parkinson-White Syndrome in your dog, you should provide your veterinarian with a detailed history of your dog’s health, including the symptoms’ onset and characteristics. Your veterinarian will conduct a comprehensive physical examination and may also order a complete blood count, biochemistry profile, urinalysis, and electrolyte panel, with results typically appearing normal. Additionally, echocardiography may reveal structural heart abnormalities often linked to WPW syndrome.
Treatment
If your dog exhibits ventricular pre-excitation without tachycardia, no treatment is necessary. However, for those diagnosed with Wolff-Parkinson-White Syndrome, treatment options include direct shock conversion (the most effective method), ocular or carotid sinus pressure, or medications. A relatively recent technique called catheter ablation, utilizing radiofrequency current, offers the opportunity to destroy or ablate accessory pathways through a transvenous catheter placed at the site of the pathway within the heart. This approach may be recommended to avoid the necessity of lifelong drug therapy.
Living and Management
The prognosis is contingent upon the severity of the underlying cause. However, most pets diagnosed with Wolff-Parkinson-White syndrome respond favorably to treatment for supraventricular tachycardia.