How to Protect Your Pet from Common Causes of Sudden Death

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PetMD Editorial
Published: July 17, 2017

By Dorri Olds

Losing a pet is an extremely painful experience for pet parents, but it can be even more difficult to cope with when the death is unexpected. Fortunately, owners can prevent some of the causes of sudden death in pets.

Your best line of defense is taking your dog or cat for regular check-ups—once a year for young pets and twice a year when they hit middle age (often when they are around 7 years old). “Have a veterinarian listen to your animal’s heart, have them do full bloodwork, the same way we humans get tests done,” advises Dr. David Wohlstadter, senior emergency clinician at BluePearl Hospital in Manhattan. “When you catch problems early, that has the best outcome.”

Here are five common causes of sudden death, and expert advice on how to protect your pet.

Heart Disease

“Heart-related diseases are the most common causes of sudden death in pets,” according to Dr. Catriona Love of the Heart of Chelsea Animal Hospital in New York City. Cardiomyopathy (a disease of the heart muscle), arrhythmias (abnormal heart rhythms), and blood clots top the list, she adds.

In dilated cardiomyopathy (DCM), the heart’s ability to pump blood is compromised, causing poor circulation, irregular heart rate, and heart failure. DCM is the most common form of cardiomyopathy in dogs. DCM has been diagnosed in cats, but they are much more likely to develop hypertrophic cardiomyopathy (HCM), which is rare in dogs. Restrictive cardiomyopathy (RCM) is the least common type.

Pets can also experience a condition called cardiac tamponade without having any previous symptoms, says Dr. Garret E. Pachtinger, a trauma center medical director and emergency clinician at Veterinary Specialty and Emergency Center in Levittown, Pennsylvania. This occurs when fluid (commonly blood) collects in the sac that surrounds the heart, which blocks the heart from normally expanding and contracting, Pachtinger explains. “In the ER, we see dogs that had been happy, playing, chasing a Frisbee and suddenly collapsed.”

Irregular heart rhythms are another relatively common cause of heart-related sudden death in pets. “There are many different types,” says Dr. Jennifer Coates, veterinary advisor with petMD. “Some cause the heart to beat faster than normal, others more slowly than normal or very irregularly, but in all of these cases, the pet’s heart is not performing its job adequately.”

Pets can also die unexpectedly from a heart attack if a blood clot forms in a coronary artery and blocks blood flow to the heart muscle. But heart attacks are much less common in pets in comparison to people.

“Heart disease is not curable, but once it is diagnosed, it’s something we can manage with diet and medication,” Wohlstadter says. “By treating it, we can significantly slow down the progress.”

Ask your vet which tests are recommended for your dog or cat, because many health risks are breed specific. For example, Cavalier King Charles Spaniels are prone to a form of heart failure called mitral valve disease, which is the leading cause of death for that breed. Your vet can diagnose a wide assortment of heart issues during regular office exams and can advise you on blood tests, X-rays, cardiac ultrasounds, and electrocardiograms.

Internal Bleeding

Internal bleeding can cause a pet to die suddenly. Common causes of internal bleeding include traumatic injuries, such as being hit by a car, or poisoning with certain types of rodenticides. “The most common is vehicular trauma,” Pachtinger says. “Falls from height would be next—especially from high-rise buildings.” 

Coates adds, “Many traumatic injuries in pets can be prevented, if pet parents take appropriate precautions. Cats should be kept indoors and dogs walked on a leash or in well-fenced areas like yards or dog parks.” To prevent high-rise falls, pet owners should ensure that all window screens are secure or keep the windows closed, and never leave pets unattended on a balcony.

Ruptured tumors can also cause life-threatening internal bleeding. “Hemangiosarcoma (a type of cancer) can develop in the spleen, liver, and heart, and if the tumor ruptures, a dog or cat can bleed out quickly,” Love says. Hemangiosarcoma is an aggressive, rapidly spreading, and sometimes silent killer. A pet can look and behave normally, then all of a sudden, the tumor bursts and the dog or cat collapses from internal bleeding.


In 2016, the ASPCA Animal Poison Control Center alone dealt with more than 180,000 cases of pet poisoning. The most common culprits are prescription medications, over-the-counter products, veterinary medicines, and certain foods, such as chocolate, grapes, onions, garlic, items that contain xylitol as a sweetener, and alcoholic beverages.

“Usually there are clinical signs before the animal just up and dies, depending on which toxin they ingested,” Wohlstadter says. “If it’s rat poison, you may see central nervous system signs like seizures. Or your pet may become weak, pale, or have trouble breathing.” But Coates adds, “On the other hand, with certain types of poisons, it’s certainly possible for a pet to look relatively normal in the morning when an owner leaves for work and for the pet to pass before the owner returns home in the evening.”

In many rural areas of the country, Love says, “sudden deaths in dogs and cats are caused by snake bites because the venom carries a large range of toxins.” If you suspect your pet has been bitten, it’s vital to get to a veterinary ER immediately. Recovery will depend on how fast a vet can begin treating your pet.

To protect your pet from toxic substances, learn which foods, plants, medications, household products, and wildlife present a potential risk and keep your pet away from them.


Heartworms, which are transmitted by mosquitoes, are extremely dangerous to dogs and cats. Coates says that “most pets will gradually develop symptoms like coughing, difficulty breathing, weight loss, exercise intolerance, and a pot-bellied appearance over time, but some may show few or subtle signs and appear to die suddenly.”

Heartworms can lead to caval syndrome, which is life-threatening, Pachtinger describes. “It can cause heart failure by blocking blood flow, which can lead to respiratory collapse and signs like a change in breathing or pink gums can be insignificant and easy to miss.”

Thankfully, heartworms are easily preventable, Love says. Speak to your vet about what type of heartworm prevention medication is best for your dog or cat.


Dog bloat, or gastric dilation-volvulus (GDV), is a twisting of the stomach that can occur in association with trapped gas. “Bloat, in lay terms, means distended or swollen, with fluid or gas,” Pachtinger explains. “With torsion or GDV, a stomach is twisted at least 180 degrees, but it can go all the way up to 360 degrees.”

While the exact cause of bloat is unknown, contributing factors may include overeating, drinking too much water, strenuous activity after eating and drinking, and anxiety. “There has been a lot of research, but it’s unclear,” Pachtinger says. “Did they eat too much or too rapidly? Did they eat, then run around? Did they drink too much water? There is probably a genetic component, but we just don’t have the answers yet.”

This life-threatening condition is most commonly seen in larger, deep-chested dogs, Pachtinger says, such as Great Danes, Standard Poodles, German Shepherds, Labradors, Golden Retrievers, and Rottweilers.

Symptoms of bloat in dogs may include swollen stomach, excessive drooling, and unproductive dry heaving. These symptoms often come on very quickly and the dog’s condition will rapidly worsen, so if you suspect that your dog has bloat, consult your vet or the nearest veterinary emergency center immediately.