Symptoms of heart failure are most common. Usually, they develop slowly over time. However, sometimes symptoms start very suddenly and are severe. Common symptoms are:

• Shortness of breath with activity or after lying down for a while, or in infants while feeding
• Swelling of feet and ankles (in adults)
• Irregular or rapid pulse
• Fatigue, weakness, faintness
• Swelling of the abdomen (in adults)
• Loss of appetite
• Cough

Other symptoms may include:

• Chest pain
• Decreased alertness or concentration
• Failure to thrive (in children)
• Low urine production
• Need to urinate at night (in adults)
• Shock

Cardiomyopathy is usually discovered when the doctor is examining and testing you for the cause of heart failure.

• Tapping over the heart with the fingers and feeling the area may indicate that the heart is enlarged.
• Listening to the chest with a stethoscope reveals lung crackles, heart murmur, or other abnormal sounds.
• The liver may be enlarged.
• Neck veins may be bulging.

A number of laboratory tests may be done to determine the cause:

• Antinuclear antibody (ANA), erythrocyte sedimentation rate (ESR), and other tests to diagnose autoimmune illnesses
• Antibody test to identify infections such as Lyme disease and HIV
• Serum TSH and T4 test to identify thyroid problems

Children will have:

• Poor growth
• Pale skin
• Difficulty feeding
• Weak pulses in the legs and arms

Heart enlargement, congestion of the lungs, decreased movement/functioning of the heart, or heart failure may show on these tests:

• Echocardiogram
• Cardiac stress tests
• Cardiac catheterization and coronary angiography
• Chest CT scan or MRI of the heart
• Chest x-ray
• Nuclear heart scan (MUGA, RNV)

Other tests may include:

• ECG
• Heart biopsy

Lab tests vary depending on the suspected cause.