Posted: 20/04/2013 at 20:37
If you are going to dig it into the soil, then I wouldn't be too concerned, particularly if you are growing ornamentals. I would be less inclined to use it as a mulch with the mess in it, generally due to the smell and unpleasantness of it all. ( you could clear the mess out)
I would not want to use it around edibles unless it had been rotted for at least a year without any more additions from the cat.
You say that the compost heap is large and has accumulated over time. I suspect that it hasn't rotted down too well and so I think that I would pull the whole lot out, and then rebuild the heap in as compact a shape as possible, if the matter is dry it can be watered as you rebuild. This would aerate the heap and should encourage a good compost. You could cover the heap to keep the cats out while it was composting (old carpet, polythene, cardboard etc).