Cardiomyopathy means damaged heart muscle. In cats this can take two forms, dilated cardiomyopathy(DCM) and hypertrophic cardiomyopathy(HCM).
DCM is very rare now in cats. It is caused by a nutritional deficiency in Taurine. This chemical is now available in all commercial cat foods and I havn't diagnosed this condition for many years now.DCM is when the heart muscle weakens and the heart chamber dilates.
HCM is however this most common form of heart disease we are now seeing in cats. The heart muscle thickens and the heart chamber gets smaller. Thus only a small amount of blood can be pumped out with each contraction of the heart muscle. Also the muscle becomes fibrotic(less elastic) and this further complicates the problem. The blood flow is congested and we see the symptoms of congestive heart failure. The cause of HCM is not completely understood at this stage. It may be associated with early exposure to a viral disease or have a genetic(inherited) cause. Ragdoll and Maincoon breeds are most commonly affected. In humans this disease is genetic and genetic markers can determine if you will get this disease.

Although the damage to the heart may have been there for some time, the symptoms will appear quite quickly. In cats, we do not see coughing like in dogs, but breathlessness, lethargy and poor appetite. The symptoms we see in cats are due to a build up of venous blood pressure causing fluids to leak out into the lungs and surrounding tissues. This condition may also cause a clot to form in the heart resulting in sudden painful paralysis in the hindquarters or even sudden death.

To confirm our diagnosis, we will do an ultrasound scan, to measure the size of the heart chambers and the thickness of the heart muscle. We may also do chest X-rays and an electrocardiogram( ECG). This disease is also associated with an increase in blood pressure and we will measure this.
A complete blood test is also important. The poor circulation of blood will also cause other organs, especially the kidney to fail.

there is no cure for this disease. The treatment will help the stress on the heart and alleviate the symptoms. We will use drugs to dilate the blood vessels that leave the heart, also drugs that drop the blood pressure. Remember blood clots can easily form in the heart chambers with this condition and drugs preventing blood clots will also be used.
If we see on the X-ray a build up of fluids in the lungs, then we will use drugs to remove these fluids.
If the heart rate is excessively high, I will use a drug to slow the rate down.
Remember, your cat can suddenly die at any time from cardiomyopathy.