Symptoms of heart disease in cats can vary depending on the severity and specific type of condition. The following are some common symptoms of heart disease in cats:

1. Difficulty breathing: Cats may have symptoms of difficulty breathing, which may be manifested as mouth breathing or increased respiratory rate.

2. Cough: Cats with heart disease may develop coughing symptoms in the later stages.

3. Decreased activity ability: Cats may become unwilling to move or play, and may feel tired easily.

4. Lethargy: Cats may be more lethargic than usual or sleep for longer periods of time.

5. Appetite change: The cat's appetite may decrease, leading to weight loss.

6. Heart murmur: Through auscultation, your veterinarian may hear a heart murmur.

7. Other systemic symptoms: Cats may also have systemic symptoms such as arrhythmia, mucosal cyanosis, decreased urine, and abnormal body temperature.

Please note that not all cats will show these symptoms, and some symptoms may also be caused by other diseases.