What Causes Sudden Death in Cats?

1 Lifespan and Hidden Illness

Life expectancy runs from about 14 to 22 years and varies greatly with lifestyle: strictly indoor cats live longest, then indoor-outdoor cats, and outdoor cats shortest because of toxins, trauma, animal attacks, and infectious disease. While this is the general pattern, an outdoor cat with good genes, nutritious food, and veterinary care can also live very long.

It is important to remember that cats are very good at hiding illness, often being sick for a long time before anyone notices. This is especially true for owners who see a cat every day yet miss subtle changes like weight loss, thinning fur, longer sleep, or a duller coat. As cats age, signs such as weight loss, less activity, and lethargy are easily mistaken for normal aging rather than disease.

2 Trauma and Poisoning

Trauma is more common in outdoor cats but can happen to any animal: being hit by a vehicle, attacked or bitten by a dog or other animal, gunshot, falls, or random crushing injuries such as being sat on in a recliner.

Poisoning from ingesting or contacting toxins and medications is more common in outdoor cats but also occurs indoors. Common toxins include antifreeze, certain flowers, acetaminophen-containing drugs, plant toxins such as Easter lily, and ingested rat poison.

3 Heart and Circulatory Causes

Heart disease often gives little or no warning. Some cats have a history of heart murmur, but others have no prior problem or symptom. A few show subtle signs such as playing less, sleeping more, reduced appetite, weight loss, or increased respiratory rate; many look perfectly fit yet suddenly show severe signs. A cat with heart disease may have trouble breathing or using the hind legs, and may cry out in pain. The most common feline heart disease is hypertrophic cardiomyopathy (HCM), in which the heart muscle thickens abnormally; feline heartworm disease can also cause sudden death.

Heart failure means the heart can no longer meet the body’s needs, usually leading to fluid in the lungs (pulmonary edema). The most common root cause is HCM. Signs include a slight drop in appetite, less normal activity, and faster breathing; some cats breathe rapidly with an open mouth, hiding symptoms until explosive, life-threatening failure appears.

A ‘heart attack’ describes myocardial infarction from coronary artery disease in people: the heart muscle receives nutrients and oxygen from the coronary arteries, and when it loses normal blood supply, a heart attack occurs.

Blood clots, also called thrombi, can arise from many health problems including heart disease. A clot reaching the brain, lungs, or hind-leg vessels can cause sudden death.

4 Organ and Metabolic Diseases

Chronic kidney disease (CRF) is common. When the kidneys fail they no longer clear metabolic wastes, letting toxins build up in the blood and producing signs such as weight loss, reduced appetite, vomiting, and drowsiness as the disease advances; some cats also drink and urinate more. It is most common in older cats but can occur at any age.

Feline urinary obstruction (UO) is an acute blockage of the urinary tract, most common in male cats, also called a ‘blocked cat.’ Typical signs are straining to urinate and crying out. Left untreated, most cats die within 72 hours.

A stroke (CVA) describes a cerebrovascular accident from interrupted brain blood supply, which stops nerve signals from reaching the body. It comes on very rapidly and can cause sudden death. Signs include difficulty walking, weakness, falling to one side, paralysis on one side of the body, and/or seizures.

5 Infection, Shock, and Blood Sugar

Severe infection, usually called sepsis, can cause a progression of signs including lethargy, anorexia, weight loss, dehydration, fever, and sudden death.

Shock is a life-threatening syndrome that causes low blood pressure and death. It can come from allergic reaction, heart injury, severe infection (sepsis), trauma, blood loss, toxins, fluid loss, and spinal-cord injury; a cat in shock can die quickly and look like a sudden death.

High blood sugar from uncontrolled diabetes can cause weakness, lethargy, vomiting, coma, and death.

Low blood sugar can cause lethargy, weakness, seizures, and sudden death, and may be a bad outcome of diabetes, trauma, and/or various infections.