Cat has heart murmur
Heart murmurs are actually quite common in older cats - many of them will have an underlying thyroid disease condition which will lead to this problem. To diagnose this problem usually requires a blood test and to evaluate the extent of damage of the heart from this condition would usually require a chest xray and possibly a chest ultrasound. In most cases this condition can be well managed if proper medical protocol is followed and you have a proactive Veterinarian, as well as being self motivated to follow the medical reccomendations. You make no mention of his age so it is hard to for me to guide you more.
If he is a younger cat, then he may have a congenital ( was born with) heart condition and will need a proper cardiac evaluation with xrays, possibly viral blood tests and an ultrasound to determine what the underlying cause may be and how to treat it.
In either case, he should have a good physical examination and appropriate diagnostic tests performed. To me it is not acceptable that you would merely be told that he will be a special needs cat in future without further recommendations. I would be surprised if your Veterinarian did not suggest any further work up. A work up should in my opinion, be recommended on any cat with a grade iii or higher ( goes up to grade iv) murmur even if they are not showing symptoms, and regardless of the grade, if there are any heart related symptoms, a medical work up should be performed or at least recommended. I unfortunately do not know the extent of the examination and what procedures were recommended to indicate whether a 2nd opinion would be warranted.
Good luck. Sounds like an interesting case. Please also be aware that the main risk with diagnostic procedures in a cardiac diseased cat, could be a sudden heart failure/heart attack situation which could result in sudden death, and this has to be factored in when deciding on doing procedures and the order of the procedures( sometimes better to do chest xrays first with little or no restraint) before restraining for blood collection.
Martin Slome DVM
Centre Street Animal Hospital
7700 Bathurst Street
Tel: (905) 771-9855