Vladimir´s passive in ARAM

So , we all know how Vlad´s passive work as far as what it does. If I buy a health item I am fine, however if I buy a Ap item , while I do gain the bonus health , I gain it as max health , not current health. So many times Vlads don´t start at full health at ARAM. Say I have no bonus health at the start of the game, so I have 543 health. I buy a Hextech Revolver and my max health goes to 599 , but my current health is still 543.