Spayed??

I had my cat spayed about a year ago. She was about two years old at the time. Here is the strange part, sometimes she still seems to go into heat. Every now and then, she starts the loud howling and rolling around. Is this normal? Help, please!!

If she seems to go into heat still, it's possible that the veterinarian didn't get everything. If this is the case, you can have a vet do an exploratory surgery, or just keep a close eye on her and make sure she doesn't come into contact with any whole males.