Migraine with Aura

I"ve been getting a visual Aura that starts off as a dot like if you get your picture taken with the flash.... the dot is like a block in my vision.... then if forms a half circle and slowly gets closer and closer till it passes past my vision... the whole process takes about 30 minutes and after the Aura passes I get a headache... During the Aura faze my speech gets affected and I cant think clearly..... the headache will last for hours and usually only goes away after a get some sleep.... sometimes I even feel it the next day and usually I feel strange and off the next day even.... Im currently taking a beta blocker to help prevent these Migraines but I still get them..... I cant take the abortive drugs because I have and arrythmia and most of the abortive drugs are high stimulants.....  i've heard high levels of Magnesium can help or vitamin B2 for preventive measures and im just curious to know if anyone has had success with this combo.... Or if anyone has any good advice to kick these headaches in the BUTT....  Thanks..Stu