Wolff-Parkinson-White-Syndrome in Dogs

Wolff-Parkinson-White Syndrome is an affliction that interferes with the electrical impulses of the heart. In this specific disorder, the arrhythmia is caused by an abnormal piece of muscle in the heart called an accessory pathway, and it can cause severely a rapid heart rate, known as tachycardia. It is most often caused by a congenital defect of the heart, but can also result as a secondary complication to acquired heart disease.

Wolff-Parkinson-White Syndrome is a rare disorder in the electrical system of the heart. An abnormal piece of muscle in the heart called an accessory pathway causes disruption to the system, often resulting in arrhythmias. Wolff-Parkinson-White Syndrome will cause an abnormally rapid heart rate (tachycardia). 

Wolff-Parkinson-White Syndrome may go undetected for many years in your canine and symptoms may come and go, depending on the overall health of your pet and current exertion and anxiety levels. Symptoms that may indicate your dog is experiencing an arrhythmia could include:

• Exercise intolerance 
• Fainting or loss of consciousness
• Lethargy
• Tachycardia (rapid heart rate)  
• Weakness

The normal heart rate for most canines is between 60 to 140 beats per minute. In a dog that is experiencing tachycardia, this can jump to double or even triple the normal rate. 

In many cases, Wolff-Parkinson-White Syndrome is caused by a congenital defect of the heart. The following defects can cause Wolff-Parkinson-White Syndrome to develop:

• Atrial septal defect - a hole between the atrial chambers of the heart
• Conduction defect - a defect in the conduction system of the heart 
• Tricuspid valve dysplasia - the valve between atrial chambers is improperly developed

This syndrome can also be caused by hypertrophic cardiomyopathy, a condition which causes abnormal thickening of the heart walls. 

Lethargy, tachycardia, and weakness can be indicative of a number of disorders including cardiac disorders (such as Wolff-Parkinson-White Syndrome), reactions to certain toxins, and even electrolyte imbalances. 

You will want to give your veterinarian a full history, including when the symptoms began and under what circumstances. Your dog will undergo a thorough physical exam, and your veterinarian will most likely run tests to analyze blood chemistry, check for possible toxins, and determine electrolyte balances. 

An electrocardiogram (ECG) may reveal the abnormal rhythm in the electrical impulses that are indicative of Wolff-Parkinson-White Syndrome, and radigraphs of the chest area could also uncover any underlying physical defects of the heart. 

Treatment for Wolff-Parkinson-White Syndrome can vary somewhat, depending on the underlying cause of the disorder. Intravenous lidocaine, defibrillation, and pressure to the ocular or carotid sinus are often required, either separately or in combination, to normalize ventricular activity. 

Once ventricular activity is normalized, a catheter ablation of the accessory pathway may be recommended. With this  disorder, the arrhythmia is caused by an abnormal piece of muscle in the heart called an accessory pathway. The accessory path is located using an algorithm and radio waves are used to destroy it, thereby stopping the source of the arrhythmia. 

Catheter ablation has a high success rate with few complications. Some bleeding and pain may occur at the catheter insertion site, and in very rare cases blood clots, fluid build-up around the heart, or inflammation may occur. 

The arrhythmia may also be treated using class 2 or class 4 antiarrhythmic medications to manage the symptoms. This treatment option is a management option and your pet will be prescribed the medication on a daily basis, most likely for the rest of their lives. 

If your pet is prescribed antiarrhythmic medications, these will need to be given as instructed by your veterinarian. 

If your pet had a catheter ablation to correct the abnormality, it is important to ensure that the catheter insertion site remains clean and uninfected. There may be discomfort for a few days after the procedure and your pet should be kept calm and comfortable. Short episodes of irregular heartbeat may occur as the tissue heals. This is a normal reaction and should abate over time. 

Physical activity and medication requirements will vary depending on the situation, as will the recovery time. Periodic electrocardiograms throughout the life of your pet will usually be recommended to monitor the heart rhythm.