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. 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 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.

Veterinary Care

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

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.

Prevention

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.