The heart has four chambers: two chambers at the top, the right and left atria; and two chambers on the bottom, the right and left ventricles. The right side of the heart collects blood from the body and pumps it into the lungs, where the blood is oxygenated. The oxygen rich blood is then collected by the left side of the heart, and from there it is pumped out into the body's various organs.
Congestive left-sided heart failure refers to a condition in which the left side of the heart is not able to push blood through the body efficiently enough to meet the metabolic needs of the body, and frequently results in blood pooling in the lungs. Low blood output from the heart causes tiredness, exercise intolerance and fainting.
Your veterinarian will perform a thorough physical exam on your cat, taking into account the background history, onset of symptoms and possible incidents that might have led to this condition. A blood chemical profile, complete blood count, urinalysis and an electrolyte panel will be ordered to check the underlying cause of the heart disease and its severity. Your veterinarian will also draw blood from your cat to check thyroid function.
Imaging studies can be used to gain a further understanding of your cat's heart condition. X-ray and ultrasound imaging may be used, as well as electrocardiogram (ECG, or EKG) recordings for examining the electrical currents in the heart muscles. These recordings may reveal any abnormalities in cardiac electrical conduction (which underlies the heart’s ability to contract/beat).