Is there any good substitute for low dose aspirin therapy(can cause buildup of uric acid) for heart disease?

No problem.: Salicylates in low dose will increase uric acid levels. However 81mg of asa would have a neglible effect. Large doses of salicylate lower uric acid. Plavix (clopidogrel) would be an expensive alternative.

Higher dose aspirin: Higher doses do not elevate uric acid the way the low dose does. Ask your doctor if this is appropriate for you.