A thorough examination of your cat will often be enough to tell your vet that your cat has heart disease. When listening with a stethoscope your vet might hear changes in the heart sounds (a 'heart murmur') or an abnormal heart rhythm. Your vet may be able to see other changes in your cat's appearance, which suggests that heart disease is present.

X-rays and ultrasound scans may also be used. X-rays will usually be needed to see if the heart is enlarged or abnormally shaped. Ultrasound scans allow measurements to be made of the heart muscle to see if it is too thick or has become stretched. Ultrasound can also let your vet see if the heart valves are working properly and if there are any holes in the heart. An electrocardiogram (ECG) records the electrical activity when the heart beats, and in cardiomyopathy the heart may have an abnormal or irregular beat which can be seen on the ECG.