Heart Attack in Dogs

A heart attack, or “myocardial infarction,” happens when blood is blocked from reaching the heart muscle (myocardium). Deprived of oxygen and nutrients, the heart muscle dies and the affected heart chamber can no longer effectively pump blood through the body. Canine heart attacks have been seen in all breeds and are very rare. Increased risk for heart attack can be seen accompanying heart disease, congenital heart abnormalities, and genetic predisposition. Heart attacks require emergency medical attention and can result in sudden death. Canine heart attacks have been seen in all breeds and are very rare. If you notice symptoms of a heart attack in your dog, keep calm and contact a veterinarian immediately.

There is little warning for a heart attack event. Collapse may be the first symptom observed. Symptoms associated with canine heart attack can include:

• Slight fever (over 103° Fahrenheit/39.4° Celsius)
• Vomiting
• Panting/abnormal breathing
• Increased heart rate (over 100 beats per minute for large breeds) (over 140 beats per minute for small breeds)
• Lethargy
• Head tilt
• Confusion/Anxiety
• Immobility
• Rigidity
• Seizure
• Collapse
• Sudden death

Causes of heart attack in dogs include:

• Tumor: Tumor masses growing on or around the heart vasculature can block blood flow to the heart muscle.
• Hypothyroidism: Thyroid gland does not produce thyroxine hormone – responsible for converting food to fuel for the body.
• Nephrotic Syndrome: Kidney damage results in loss of protein involved in preventing blood clot formation. Blood clots are one cause of canine heart attack.
• Bacterial infection: Infection in the body can lead to inflammation and blockage of blood flow to the heart muscle.
• Vasculitis: Blood vessel inflammation as a result of infection, immune-mediated disease, or other injury to endothelial linings. Results in narrowed vasculature.
• Atherosclerosis: Plaque builds up in the arteries, restricting blood flow or rupturing arteries. Rare in dogs but has been reported in some breeds.
• Coronary artery disease: Extremely rare in dogs. Occurs only with severe hypothyroidism and associated high serum cholesterol levels.

If you notice symptoms of a heart attack in your pet, keep calm and carefully wrap the pet in a blanket to calm him. Do not attempt CPR unless you have been professionally trained and know it is necessary. CPR can do more harm than good if it is not needed. Do not attempt to feed or give water in case of vomiting/asphyxiation. Keep young children away from the pet as pain and panic can cause aggressive behavior.

Calmly place your palm on the left side of the chest to feel the heart rate. Count the number of beats in 15 seconds and multiply your answer by 4. This gives you the number of beats per minute. Normal heart rate in dogs will be around 60-140 beats per minute depending on their size. Transport your pet to the veterinarian as soon as you can.

If your pet collapses, keep calm and carefully wrap her in a blanket and transport her to the veterinary clinic. Try to keep the events leading up to the collapse in your mind so you can report them to the veterinarian.

The veterinarian will collect any history as to what led up to the symptoms or collapse event. The vet will listen to the heart for any murmur, irregular pulse, or arrhythmia. Laboratory diagnostics can reveal valuable information as to cardiac function and possible causes of symptoms you are observing.

• Electrocardiography (EKG): Determines cardiac electrical impulses and measures arrhythmias.
• Complete Blood Cell Count (CBC): Determines red and white blood cell count, can detect possible infection.
• Biochemistry: Examines kidney and liver function.
• Urinalysis: Examines kidney and metabolic function.
• Thyroid: Examines thyroid gland function.
• Echocardiography: Detects fluid or masses around the heart, heart valve function, heart muscle and pericardial health.
• Chest X-ray: Determines size of heart, fluid around heart, possible masses.

A Holter monitor or ambulatory EKG is useful to monitor heart health at home. Electrodes are taped onto the chest and the device is strapped on the back for 24 hours. The heart rhythms are recorded and times of rest versus times of exercise or stress are reported by the owner. The recording is analyzed for abnormal heart activity.

Initial treatment may involve resuscitation and supportive care, depending on seriousness of the event. The initial goal is to regain normal heart activity. Medications may be used to thin the blood for ease of circulation. Hospitalization is often necessary to continue heart monitoring until the veterinary staff is certain the pet is stable.

A variety of medications are available for cardiac abnormalities depending on the identified cause. Pacemaker implants are more widely available for canines predisposed to heart problems. Surgery may be required to remove any mass that may be obstructing blood flow to or from the heart. Thyroid hormone replacement medications are common and available. Various diets and medications may provide preventive/supportive care for renal disease if damage is not severe. Antibiotics may prevent further damage to vessels and heart lining resulting from infection or inflammation. Anti-arrhythmic medications can correct arrhythmias.

Once the pet has become stabilized, potential of recurrence is based on cause of the problem and severity of the myocardial infarction. Surgery and medications can extend the life of the pet for many years when the issue is diagnosed early and treated responsibly. Medications may need to be administered over the remaining life of the pet. In the case of collapse, your pet may need to remain in the hospital overnight or longer for monitoring.

The life of your pet after a heart attack will depend on the severity of the attack and its cause. Lifelong treatment may be required in the case of hypothyroidism, renal or heart disease. Regular heart monitoring in the veterinary clinic or with an ambulatory EKG recorder may be necessary to ensure stabilization over the first few weeks or months, possibly a few times per year for younger pets.

Activity restriction may be necessary for the first month while the pet stabilizes. Owners may want to become familiar with normal heart and breathing rate of their pet so rates can be taken after various times of high activity or stress. Change of diet or dietary supplements may be suggested by the veterinarian depending on the cause and severity of the event.