Cat with enlarged heart and heart murmur

. I have a male cat Oreo that’s about 5, I took Oreo to the vet clinic last week for his yearly shots, the vet was listening to his heart and then told me to listen, he said Oreo has an enlarged heart and a heart murmur, they done x-rays to verify. The vet gave me a script for dogs and had to be ordered, I am waiting on it to come in, the Vet ordered a medication called Pimobendon, my question is, is this also used for cats with heart murmurs and how effective is this medication

Hello.  Bear in mind that a heart murmur is only a symptom, not a disease in itself.  Several different diseases can cause heart murmurs in cats and it is important to have an idea which disease the cat has, because different ones are treated differently.  My understading is that Pimobendan does not have a license in cats in the UK at this time but has been demomstrated to help / increase lifespan in cats with certain diseases eg hypertrophic cardiomyopathy, if started before a certain stage of heart failure.  However, this really is a question for the vet doing the prescribing who will know what is going on in your cats' case and will usually be able to advise appropriately for the patient in front of them. They can obtain further information about the stats supporting a claim, from the drugs company or from an expert in the field, such as Luca Ferasin, a cardiac specialist widely known for educating vets about heart disease in cats and dogs.