About a month leading up to the first heat you will notice a change in the V of the Vizsla (ha, no pun intended).. more swelling and looseness.. totally normal. You might notice other dogs are beginning to notice her more too. This can last quite a while as girls can go slowly into their first heat. You will find she might get more moody, restless, whiny, needy, mopy, and just unsettled. When she goes into heat you will understand why she was like that the month before lol. Just how it goes.
During heat I find my girl has less energy and sleeps quite a bit... and still shows signs of all of the above. This is the big thing to remember, when you first notice that bleeding/dripping mark it on calendar
. Count 21 days out from that and you have an estimate on her cycle. Some can be slightly longer or shorter but most follow that routine. These 21 days your safest bet is to have her ON LEASH. She will not be her normal minding self, and you can't blame her for that. So don't take chances. Watch her when she is outside, even in a "secure" fence. She not only will be hormonal but neighbor dogs pick up on it too and might come knocking. It's amazing how males will travel for girls... and I have known many girls to get lost when they are in heat because their ears just magically turn off.
So play it safe please and keep her heavily monitored for those 21 days... Especially after the first week around day 11.. when they typically are most fertile.
As far as care while in heat.. We bought several pairs of the cotton fancy pants... we put liners in and keep things clean. In the house she wears them.. not in the yard or her crate. You may want to give her more crate time than usual so she can have a break from the pants and take care of business.
Hope that helps, I never found Luna being in heat to be that big of a deal lifestyle wise. Kinda enjoyed the lower exercise requirements. She is happy to wear her fancy pants and otherwise is pretty normal.