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Myocardial Infarction in Dogs

Much like in humans, a heart attack (or myocardial infarction) in dogs occurs when blood flow to a portion of the myocardium (the heart's muscular wall) is blocked, causing the premature death of a portion of the myocardium. Generally, this is due to the formation of a blood clot (or thrombus) within the blood vessels or heart.

Heart attacks are rare in both dogs and cats.

Symptoms and Types

• Weakness
• Lethargy
• Vomiting
• Difficult breathing
• Obesity
• Low-grade fever
• Lameness
• Increased heart rate
• Collapse
• Sudden death

Causes

• Atherosclerosis and coronary artery disease
• Nephrotic syndrome
• Vasculitis (inflammation of blood vessels)
• Hypothyroidism
• Bacterial infection
• Tumor(s)

Diagnosis

You will need to give a thorough history of your dog’s health, including the onset and nature of the symptoms. The veterinarian will then conduct a complete physical examination, paying close attention to the dog's cardiovascular system. Various laboratory tests -- such as complete blood count (CBC), blood culture biochemistry profile, and urinalysis -- will be used to help identify the underlying cause of the heart attack.

Blood testing may reveal an increased number of white blood cells (leukocytes), often seen during infections. The biochemistry profile, meanwhile, may show abnormally high levels of liver enzymes or abnormally low levels of T3 and T4 hormones (especially seen in dogs with hypothyroidism). Echocardiography is another excellent tool used to evaluate of cardiac abnormalities.

Treatment

The course of treatment will depend on the underlying cause of the heart attack and the complications associated with the myocardial infarction. Initial treatment also involves using medication(s) to dissolve the thrombus and restore blood flow to the heart muscles.

In severe cases, especially those with irregular heart rhythms, dogs will hospitalized until they are stabilized.

Living and Management

The prognosis largely depends on extent and duration of problem. In addition to regular monitoring of heart and laboratory testing during treatment, your veterinarian will recommend restricting the dog's activity during and after treatment.