Hi Steve,
I don't have any particular recommendations for cardiac cases.
If animals are in uremic crisis, then low protein is essentially the only way to go, but at that point, I don't see many animals surviving once the patient has progressed to mucosal ulceration and necrosis, so we generally euthanize those patients.
Any patient not in crisis, I choose diet based on the pathological process occuring in the kidneys. If ischemic necrosis, with UPC ratios less than 2, I use the higher protein levels with Rehmannia Eight. This supports maximal filtration, phosphate and creatinine clearance while avoiding renal hypertension.
For GN cases, there is no one macronutrient that is well tolerated, so I go with the animal's whims during this inflammatory stage and use Susan Wynn's low phosphorus renal failure diet (available in the 2008 AHVMA conference proceedings at www.ahvma.org). For herbs, I use XCHT or SRT.
My goal is to shift those cases to a chronic inflammatory state that then responds well to improved perfusion and blood flow using higher protein diets and Rehmannia Eight.
Hope that helps,
Steve