10 Causes of Feline Heart Murmur There a number of causes resulting in feline heart murmurs. Some conditions may be resolved with surgery.
  1. Sometimes a cat heart has some abnormality or defect with the heart wall itself or the valves within the heart due to genetics (hereditary). Often a kitten is born with a heart murmur that he will grow out of in several months. This condition is not unusual and does not impair the cat heart. Often surgery can repair deformities in the heart valves.
  2. Severe anemia resulting from flea and/or tick infestations can affect the heart. Nutritional supplements can treat the heart murmur.
  3. The narrowing of the outflow area of the pulmonary artery at the exit from the right ventricle of the heart is called pulmonic stenosis. Here the murmur is the result of the abnormal turbulence of outgoing blood meeting resistance.
  4. The same condition as above except occurring in the aorta outflow area is called aortic stenosis.
  5. Tetralogy of Fallot is a complex defect affecting emerging arteries of the heart and more than one segment of the heart. Pulmonic stenosis causes the heart murmur.
  6. A hole in the interior wall of the pumping chambers is called ventricular septal defect (VSD) and if the hole is very large may not even result in a murmur since little to no turbulence occurs.
  7. One of the more common causes is mitral valve dysplasia, which is a defect resulting in a leaky valve causing the murmur from the turbulence of blood reflux.
  8. Patent ductus arteriosus (PDA) results when the duct in the fetal heart does not close after birth. This produces a shunting of blood, which may result in a heart murmur only if the shunting of the blood occurs from left-to-right side of the heart.
  9. Hyperthyroid disease is the leading cause of heart murmurs in cats. This disease can be treated using a combination of medication therapies and/or surgery.
  10. The cat heart disease feline cardiomyopathy can also contribute to heart murmurs. This disease causes the heart muscles to change shape, stretch or thicken making it difficult for the heart to work properly. Often medications will improve the efficiency of the heart by reducing the workload on the heart and increasing the elasticity of the heart muscles themselves.
For the most part, heart murmurs are not life threatening. Cats can outgrow them or surgery and/or medications can correct them.