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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.

Treatment

In some dogs, atrial standstill is not a life-threatening condition and no hospitalization is required. However, in others it may be serious enough to require immediate intensive care. Such animals typically have an abnormally high blood potassium level or are suffering from severe dehydration. In these cases, intravenous fluid therapy is used to stabilize the animal. If the dog's heart rhythm cannot be rectified by ordinary means, a pacemaker may be surgically implanted into the chest or abdomen. This small medical device helps control the abnormal heart atria activity.

Living and Management

The prognosis of the dog depends on the underlying disease causing the heart rhythym disturbance. If it is corrected quickly and (when present) hyperkalemia is reversed, the long-term prognosis is excellent.

Your dog will require rest in a stress-free environment, away from other pets and active children, to help control the symptoms of persistent atrial standstill. Even with a pacemaker, however, the symptoms of lethargy and weakness may persist. Dogs with pacemakers also require regular follow-up exams and periodic ECGs to monitor the effectiveness of the device and the heart's rhythm.