Syncope (Fainting) in Cats


Overview of Fainting in Cats

The term syncope (or fainting) refers to a brief period of unconsciousness due a lack of blood flow or oxygen to the brain. Syncope causes collapse, which may last from seconds to minutes in cats. Most fainting “spells” are due to low blood pressure or lack of oxygen delivery to the brain (cerebral hypoxia). Syncope is a clinical sign, not a diagnosis or primary form of heart disease.

Blood pressure depends mostly on heart and blood vessel function. Accordingly, disorders of the heart or vessels (cardiovascular system) are the most common causes of syncope. Often, the cause is an electrical disturbance of the heart (slow or irregular heart activity). At other times, there is a structural problem of the heart (such as an abnormality of the heart muscle or a valve) or pericardial disease (the sac around the heart). Recurrent syncopal attacks may cause brain injury.

Other conditions that can lead to syncope in cats include: severe respiratory disease or severe coughing; metabolic (body chemistry) disease; endocrine (hormonal) disorders; dysautonomia (abnormal function of the involuntary nervous system); anemia and drug therapy. The brief event ends with rapid and complete recovery, in most cases.

What To Watch For

  • Sudden weakness – Syncope often begins with sudden weakness that quickly progresses to ataxia (incoordination); ending with a transient loss of consciousness. Often fainting is precipitated by sudden activity or exercise.
  • Crying out – Some pets vocalize (cry out) immediately prior to losing consciousness and there may be a “distant” or “glassy-eyed” appearance to the face.
  • Leg rigidity – The forelimbs may briefly become rigid and the head may be pulled back, causing confusion with a seizure disorder (such as epilepsy).
  • Incontinence – which is loss of urinary or bowel control.
  • Diagnosis of Syncope (Fainting) in Cats

    Diagnostic studies should include:

  • A history (including medication review) and physical examination with an emphasis on stethoscope examination (auscultation) of the heart and lungs.
  • Exercise test – pre- and post-exercise heart examination
  • Measurement of blood pressure
  • Blood tests, including a blood glucose, blood biochemical tests, and complete blood count
  • Electrocardiogram (EKG) – this can include a routine EKG, an ambulatory (tape-recorded) EKG, or an “event monitor” (an EKG activated by the pet’s owner). The latter two EKG examinations often require referral to a specialist.
  • A chest X-ray (thoracic radiograph) – especially when indicated from history and physical examination
  • Pulse oximetry, if there is evidence of lung disease
  • Heartworm test in appropriate areas
  • Ultrasound examination of the heart (echocardiogram)
  • Additional laboratory (blood) tests, such as those evaluating endocrine (hormone) function
  • Treatment of Syncope (Fainting) in Cats

    The treatment of syncope must be tailored to the underlying cause. In most cases, syncope is an historical complaint, but the cause of the problem must be sought and managed to prevent further occurrences.

    Home Care

    Optimal treatment for a pet with syncope requires a combination of home and professional veterinary care. Follow-up can be critical. Administer prescribed medication(s) as directed, and be certain to alert your veterinarian if you are experiencing problems treating your pet. Exact follow-up depends upon the cause.


  • In general, syncope cannot be prevented unless the precipitating event can be avoided. Try to avoid possible precipitating events, such as excitement or vigorous exercise.
  • Avoid collars which pull around the neck.
  • Your veterinarian may also recommend stool softeners or cough suppressants, if needed.
  •  In-depth Information on Syncope in Cats

    Syncope (fainting) must be distinguished from brain dysfunction or weakness related to neurologic disease (such as epilepsy), stroke, neuromuscular disease, orthopedic (bone and joint) diseases and metabolic disorders, such as hepatic (liver) failure. Syncope can occur in any breed and in cats of any age.

    As there are dozens of reasons for syncope, your veterinarian must formulate an often-detailed evaluation to make a correct diagnosis. The conditions most often confused with syncope are seizure disorders (epileptic fits), metabolic (body chemistry and hormone) diseases, and disorders of muscle, bone and joints (musculoskeletal diseases).

  • Epilepsy and other true seizure disorders are electrical disturbances of the brain
  • Narcolepsy/cataplexy – rare sleep disorders (inappropriate sleep)
  • Hepatic encephalopathy – a type of abnormal brain function caused by liver disease or blood vessel malformations involving the liver
  • Hypocalcemia – low blood calcium causing muscle tremors (shaking), weakness, collapse or seizures
  • Hypoglycemia – low blood sugar from metabolic disease, cancer, infection, insulin overdose in a diabetic cat or the malicious injection of human insulin.
  • Adverse drug reaction – low blood pressure associated with a medication prescribed for a cat (such as a diuretic drug or vasodilator drug prescribed for heart failure)
  • Illicit drug intoxication – malicious administration (or exposure to) a drug designed for human use in a cat
  • Neuromuscular diseases leading to profound weakness or collapse (examples include myotonia congenita, and myasthenia gravis)
  • Severe hypokalemia – low blood potassium leading to extreme muscular weakness

    You can assist in the diagnosis by observing and writing down answers to the following questions:

  • Can you describe the fainting (syncopal) event from beginning to end?
  • What situation(s) precipitate the fainting?
  • Is there any relationship to rising, exercise or excitement?
  • What is the total number of events that have been observed?
  • Does the event occur immediately after a bout of coughing?
  • What color is the tongue and mucous membranes – pink (normal), white or blue?
  • Is there any “paddling” of the legs, facial contractions or excessive salivation?
  • How does your cat behave after the “spell” – is behavior relatively normal or does your cat seem confused or have other abnormal behavior?
  • Has the problem been diagnosed or treated before? If so, what was the response to treatment? (take any medication bottles to the veterinarian with you)
  • If possible, feel for your cat’s heart rate during the syncopal event and try to count the number of beats in 15 seconds.
  • Be aware of your cat’s general activity, exercise capacity and interest in the family activities.
  • Keep a record of your cat’s appetite, ability or inability to breathe comfortably and note the presence of any symptoms such as coughing or severe tiring.
  • If fainting occurs with difficult breathing or persistent blueness (cyanosis) of the gums and tongue, it is probably an emergency. See your veterinarian promptly!
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