That's a tough one! I agree, you don't want to sentence this cat to a lifetime of immunosuppressive drugs!
ECG is actually an allergic response in a great many of these cats. Strict flea control and minimizing exposure to allergens (both airborne and in food) are fundamentals of treatment.
I have had some success with:
- hypoallergenic diets (canned, raw, or homemade, not dry)
- oral Vitamin E (puncture a gelcap with a needle and squeeze a drop or two on your finger--most cats love it and will lick it off voluntarily, but if not, mix with food)
- classical homeopathy
Other holistic vets find that herbs (western or Chinese) or acupuncture will do the job. I think homotoxicology (a form of homeopathy) would work very well. NAET is also a good candidate (www.vetNAET.com
Omega-3 fatty acids have been reported to eliminate eosinophilic granulomas. That's certainly worth a try! I recommend Nordic Naturals brand. Their cod liver oil does not contain added vitamins D and A, so is much safer than others on the market. They have several fish body oil products also.
Of course, because this condition is due to an overactive immune system, you definitely don't want any more vaccinations for this cat, ever!