Causes and treatment for fainting in older dogs

Disclaimer: This article, its content, and its related references do not constitute veterinary advice and should not be considered a substitute for veterinary care. If your pet is showing any symptoms that could indicate a medical emergency, please seek immediate emergency care.

Fainting, or syncope, is a symptom that can occur with many age-related health issues in senior dogs. Heart disease, respiratory illnesses, and other health conditions can lead to the brain being temporarily deprived of oxygen or blood, resulting in a temporary loss of consciousness. If you believe your dog has fainted or if your dog has fainted in the past, read on to learn:

• What a syncopal episode looks like
• Possible causes of syncope in senior dogs
• How patients with syncope are diagnosed and treated
• What to do if your dog has fainted

Many age-related diseases can result in reduced cardiac output, low blood sugar, or difficulty breathing. These problems can result in a fainting episode, typically lasting less than a minute before the affected dog spontaneously regains consciousness. Treatment methods vary depending on the underlying cause of the syncopal episode(s).

Syncope, or fainting, is a temporary loss of consciousness that occurs when the brain doesn’t get enough oxygen. After about a minute, episodes of syncope are followed by a quick, spontaneous recovery. During an episode, dogs may or may not lose control of their bladder or bowels.

Fainting in dogs is caused by a lack of oxygen to the brain. This can occur due to heart problems, respiratory issues, or other health conditions that lead to low oxygenation or blood circulation. Syncope is a clinical sign of an underlying health issue rather than a condition itself.

“Fainting may or may not be an emergency,” states Dr. Jo Myers, a veterinarian on the Vetster platform. “Most fainting episodes are not emergencies at that precise time, especially if they are not related to severe cardiovascular disease. It’s more crucial to seek emergency veterinary care when your dog collapses unexpectedly if they don’t return to normal after a minute.” If your dog appears to have fainted and is fine again after a minute, it’s still best to talk to a veterinarian as quickly as possible because it can be a symptom of severe underlying disease.

Syncope vs. seizure

Syncope in dogs can be difficult to distinguish from seizures or other conditions that cause a dog to collapse. The main differences between syncope and seizures are:

• Duration of episode
• Recovery time
• Presence of repetitive, uncontrollable muscle contractions

Dogs who faint usually appear fine one second and then go limp and fall to the ground the next. Typically, a fainting spell lasts for less than a minute. They may vocalize when they first fall down, and sometimes their limbs gradually stiffen. They may or may not lose control of their bladder or bowels, and they remain unresponsive until they start to wake up. Dogs who have fainted usually seem unaware of what has happened and are back to normal quickly.

Seizures also cause a dog to collapse but are usually violent, with spasms of rapid muscle contractions across the body. They typically last for at least two to three minutes and are accompanied by signs such as paddling limbs, drooling, and biting at the air. It usually takes dogs a prolonged period of time to fully recover from a seizure, and their behavior may appear strange for hours after the event.

In both syncopal episodes and seizures, the dog falls suddenly to the floor, goes unconscious, and may lose control of their bowels, vocalize, or stiffen their limbs. However, dogs having a seizure have repeated muscle contractions in their limbs, while a dog who has fainted may just go limp or have only a gradual stiffening in the legs. Syncopal events usually last less than a minute, while seizures may last longer and cause disorientation or altered behavior for several hours.

Since syncope is caused by a lack of oxygen or blood flow to the brain, it’s more likely to occur following exercise. Seizures are caused by abnormal electrical activity in the brain, which can happen at any time, even in the middle of a deep sleep. Noting what your dog was doing when the episode started, the length of the episode, symptoms during the episode, and how your dog behaved after they regained consciousness can be valuable information for your veterinarian.

Syncope can occur in any dog; however, there are many age-related diseases that can lead to fainting, so senior dogs are at an increased risk. Dogs may faint due to cardiac diseases, respiratory conditions, and other health issues that lead to poor blood circulation or low oxygenation.

Heart disease

Cardiac disease is the most common cause of syncope in senior dogs. Cardiac syncope may be due to:

• Abnormal heart rhythm (irregular, fast, or slow heart rate)
• Inadequate cardiac output, meaning the heart isn’t pumping with enough strength or volume
• Obstruction of blood flow

There are many heart conditions that can cause these issues, leading to syncope:

• Dilated cardiomyopathy
• Congestive heart failure
• Hypertrophic cardiomyopathy
• Mitral valve disease
• Congenital heart defects or structural abnormalities
• Heartworm disease
• Cardiac masses or tumors

These conditions can deprive the brain of blood carrying oxygen, glucose, and other nutrients, causing a brief loss of consciousness.

Respiratory issues

The respiratory and circulatory systems work closely together to bring oxygen to the brain and other parts of the body. When respiratory diseases affect a dog’s ability to bring in oxygen, the brain may become starved of it, leading to episodes of syncope. Examples of respiratory conditions that can lead to syncope include:

• Brachycephalic airway syndrome
• Upper respiratory infections
• Tracheal collapse
• Pulmonary hypertension

Respiratory distress can also occur secondarily to congestive heart failure.

Brachycephalic dogs—breeds with a flattened snout—and dogs with other types of respiratory issues can develop tussive syncope, or “cough drop,” which is when fainting is caused by coughing. In these cases, syncope is caused by temporarily increased pressure around the heart, changing cardiac output, or decreased pressure around the brain.

Cough-induced syncope is most often diagnosed in brachycephalic breeds. Accidents or injuries that result in a blocked airway or inability to breathe properly can also cause a dog to faint, such as a tight collar, choking, drowning, or an injury to the neck.

Other health conditions

Other abnormalities that can lead to syncope in dogs include:

• Low blood sugar (hypoglycemia)
• Anemia
• Electrolyte imbalances
• Severe vomiting or diarrhea

There are many health conditions that can cause these changes, such as:

• Parvovirus
• Cushing’s disease
• Addison’s disease
• Gastrointestinal diseases
• Various neurologic diseases

Diabetes mellitus may also play a role because dogs being treated for it may experience some degree of hypoglycemia. In addition, injuries to the head, throat, or chest can affect the brain, airway, or heart and cause a dog to faint.

The underlying cause of a syncopal episode can be difficult to determine at first. Dogs are often back to normal by the time they reach a veterinarian. The first step is for a vet to determine if the dog fainted, had a seizure, or collapsed due to something else.

A physical examination and medical history, including what was happening right before the episode, are typical first steps in a diagnostic evaluation. During the physical exam, a vet may identify a heart murmur, abnormal heart rate or rhythm, abnormal breathing sounds, or other respiratory or cardiac abnormalities. Noting behavior or signs prior to the event may aid in diagnosis. These might include:

• Coughing
• Exercise
• Overexcitement
• Unusual behavior

Noting how long the episode lasted and how your dog behaved after they regained consciousness can also help determine whether the episode was syncope, seizure, or something else.

Based on the physical examination and clinical history, diagnostic tests may be recommended, such as:

• Blood tests
• Resting electrocardiogram (ECG)
• Urinalysis
• Imaging, such as X-rays or ultrasound, including an echocardiogram (ultrasound of the heart)
• Neurologic examination

In some cases, monitoring the heart rate and rhythm over time may be recommended. This can be done with one the following:

• Holter monitor: A wearable ECG monitor that continuously monitors the heart
• Event monitor: A monitor worn for one to two weeks that’s manually activated when an event occurs

Treatment of syncope varies depending on the underlying cause. The goal is to treat any underlying health concerns and avoid activities that may result in recurrent syncope. Treatment may involve:

• Heart medication to improve cardiac function
• Treatment of injury or accidents
• Pacemaker implantation
• Antibiotics, antiparasitics, or antifungals for infections
• Management of chronic health issues
• Surgery

It’s important to get an accurate diagnosis in order to receive effective treatment from a veterinarian because there are so many conditions that can lead to syncope.

Knowing what to do when their dog faints can help owners stay calm and help their pets. Dogs who faint usually return to normal before you have a chance to do anything about it. If it’s safe to do so, you may try to elevate the hindquarters and position the head down to improve blood flow to the brain. Do not attempt to give any medications unless instructed to do so by a veterinarian. Dogs who have fainted usually return to normal after less than a minute.

Seek emergency care if your dog does not return to normal after a minute or two or if they’re having difficulty breathing. It’s best to contact a veterinarian if your dog has fainted. Depending on your dog’s background, your vet may or may not want to evaluate them right away.

If you’re unsure if your dog has fainted or lost consciousness for another reason, do not try to reposition them or cover them with a blanket. If they seem normal after they have woken up, a virtual care appointment can be a great way for a vet to evaluate your pet quickly at home and provide timely, expert advice.

What is the most common cause of syncope in older dogs?

Cardiovascular disease (heart/cardiac disease) is the most common cause of syncope in senior dogs. Cardiac disease is common in seniors and can result in irregular heart rhythms, heart rates that are too fast or too slow, or inadequate cardiac output. This can cause a lack of oxygen-carrying blood in the brain, leading to a syncopal episode, or fainting.

How can you tell the difference between syncope and seizures in dogs?

Syncope, or fainting, is a momentary loss of consciousness due to a lack of oxygen or blood in the brain. Episodes of syncope usually last less than a minute, and dogs return to normal when they have regained consciousness. Seizures are caused by abnormal brain activity. Most seizures in dogs last longer than a minute and cause neurologic signs, such as violent muscle spasms, paddling, and biting at the air. Dogs who have regained consciousness from a seizure often behave abnormally for a period of time while they recover.

What should I do if my dog faints?

A dog who has fainted usually returns to normal on their own within about a minute, so you don’t need to do anything. If you’re unsure if your dog has fainted or lost consciousness for another reason, do not move or give them medications without the approval of your vet. If you’re positive your dog has fainted, you might try to position them with their head down and hind end elevated to increase blood flow to the brain. It’s best to connect with a vet promptly, even if your dog has woken and appears normal again.