Fixed cat in heat, is that possible?!

Question
I've been reading many posts on cats in heat, but they all say they are about to be fixed. This cat I have is, I was told, about 7 months old and was also told that she was fixed. The man who owned her before said her previous owners fixed her, then my mother who owned her before me, said they took her to a vet and said she was fixed. (Don't know if I can trust any of their answers.. buts lets just assume we can!)
  If my cat is in heat, then why does she act like she is in heat? She cries so much and so loud she sounds like a baby crying. She REALLY wants to go outside. And she keep attacking our new puppy. She has been attacked by cats before, and had a hard life up until now, with owners and other animals. Is she attacking the puppy for no reason because she just scared? Or is it because she is in heat? She's not bleeding. And.. like I've already said.. cried ALL the time!! I think I've had 6 hours of sleep in the past 3 nights! My mom said she did this before too when she first got her, and I just got her myself. What is going on?! Please help! Thank you

Answer
Hi Vanessa,

It is possible for there to be a tiny bit of ovarian tissue left behind during spay surgery, and even a tiny bit can be enough to produce the hormones that make your cat go into heat. So it is possible this is happening even if she is spayed. The only solution if this is the case is a second surgery to find and remove the leftover tissue. You'll have to consult with a vet on how to proceed, and to find out if this could be the problem. They can test her hormone levels.

However I think it's far more likely that your cat is just settling in. Cats are very upset by moving, they are territory-oriented and don't understand being forced to relocate. It takes weeks for them to get used to new surroundings, you didn't say how long you've had her - if only a few days be patient she will settle in. Here are some tips on how to help her feel more comfortable in her new home:

http://catnet.stanford.edu/articles/careguide.html

To get some sleep, first make sure you play with the cats before bed time. Get them tired out by having them chase a laser pointer or a feather on a string toy (always store these somewhere they can't reach when no in use - the string can be a choking danger). Try to establish a very strict routine, with meal times and play times always at the same time of day. This is very reassuring to a cat and will help calm them. Soon they will learn when is play time and when is sleep time! When they make noise during the night do not take any notice - even to tell them to be quiet is giving them attention and may make things worse. Ignore them, use earplugs if you must!

Also you can add some tryptophan (an amino acid found in cooked turkey that makes mammals feel sleepy and calm) to her dinner. Tryptophan can be found at most health food stores and online as capsules, just pull apart one 500mg capsules and put half of it (250mg) in her dinner each night.

More on cat nutrition and behavior:

http://www.catnutrition.org/clienthandout.html

Good luck!