Heart Beat Problems (Standstill) in Cats

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Atrial Standstill in Cats

If ECG (electrocardiogram) findings identify missing P-waves in the cat's atria, it is probably suffering from a rare heart rhythm disturbance called atrial standstill. A measure of the electrical activity of the atria (the top two chambers in the cat's heart), P-waves that are absent may be an indicator of a more serious underlying disease.

Atrial standstill can be temporary, persistent, or terminal due to complications such as heart failure. Along with absent P-waves, the ECG of the cat 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)


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


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.


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