Atrial Standstill in Dogs

Atrial standstill is a rare heart rhythm disturbance characterized by abnormal ECG (electrocardiogram) findings. Specifically, the ECG identifies missing P-waves, a measure of the electrical activity in the atria, the top two chambers in the dog's heart.

Atrial standstill can be temporary, persistent, or terminal (due to complications such as heart failure) and is most commonly seen in English springer spaniels. Along with absent P-waves, the ECG of the dog may demonstrate a slow heart rate with regular or irregular rhythm.

Symptoms and Types

• Lethargy
• Muscle wasting
• Slow heart rate (bradycardia)
• A spontaneous loss of consciousness (syncope)

Causes

• Abnormally high concentrations of potassium in the bloodstream (hyperkalemia)
• Heart disease, especially those associated with the atria (e.g., atrial myopathy)

Diagnosis

Although routine laboratory tests, including complete blood count, biochemistry profile, and urinalysis, are conducted on the animal, often atrial standstill is confirmed through ECG (electrocardiogram) findings. Other common findings include abnormally high levels of potassium and sodium in the blood -- both of which are only found with a biochemistry profile. These results may also indicate abnormalities related to other concurrent diseases. Echocardiography, meanwhile, will help your veterinarian diagnose the type of heart disease and the severity of the issue.