Q. What symptoms would a dog present when having a heart attack? Can the cardiopulmonary resuscitation methods used on humans be used on dogs?

A. Dogs with heart disease can show a variety of signs, depending on the specific type of disease, the dog's overall condition, the rapidity of onset of disease and other underlying or contributing conditions. Acute heart attacks such as those suffered by people are not commonly seen in dogs.

Dogs develop two major types of degenerative heart disease. Genetics play a significant role. Small- and medium-size breeds tend to develop chronic disease of the heart valves. This valve degeneration leads to abnormal backward flow of blood in the heart, which, over time, causes the heart muscle to stretch. Muscle stretching and thinning result in chamber enlargement, which contributes to further valve incompetence and failure.

Large and giant breeds are more susceptible to primary diseases of the heart muscle. These conditions cause thinning or thickening of the heart's muscular walls, causing the chambers to become either enlarged or too small. Disease also causes abnormal electrical activity, or

arrhythmia, which can result in inefficient and uncoordinated pumping of the heart chambers.

In both major types of degenerative heart disease, the heart usually enlarges and attempts to beat harder and/or faster to compensate, causing it to become further exhausted and diseased. In left-sided CHF, the blood backs into the lungs; in right-sided CHF, it backs into the liver and abdomen. Both types of failure can occur simultaneously.

External signs depend on the type and stage of disease and usually worsen as heart disease progresses. Primary cardiomyopathies tend to progress more rapidly than chronic valve disease.

Early signs usually include weakness, reduced activity, decreased exercise tolerance, abnormal breathing patterns and coughing. Coughing may be the first. The cough is usually low and nonproductive initially and tends to be worse at night and with exercise. Some dogs faint or collapse. Loss of appetite and weight can occur in later stages.

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