I am sorry to hear about Cindy's heart. I am a veterinarian, and will do my best to help.
What tests have been done to diagnose her heart and kidney disease? Do you have the results of blood tests and urinalysis?
Was an echocardiogram done to see if she just has a murmur or actually has heart disease? Cats can have an "innocent" heart murmur, or a heart murmur can be sign of a heart condition, such as cardiomyopathy.
I also would test her thyroid levels. Many older cats with heart murmurs have hyperthyroidism.
I do like benazapril, or Benefortin, for both heart disease and kidney disease. If she has protein in her urine, I would especially recommend it.
There is a supplement called Azodyl that helps some cats with chronic kidney disease. Fish oil is another good supplement.
It would help to see her test results, to see if her phosphorus is elevated, if her potassium is normal, if her calcium is normal, as well as her kidney numbers (BUN and Creatinine) and if there is protein in her urine.
I hope you can see what I am writing in this live chat. I am not seeing responses from you. I will try another way to connect with you if I don't hear from you soon.