My heart doctor had put me on toprol xl for my heart arrhythmia b...

My heart doctor had put me on toprol xl for my heart arrhythmia but I was also having really bad dizzy spells and feeling like I want to pass out before the toprol.I did pretty good on it for a good while.then out of no where the dizzy speels started back up and feeling like I want to pass out.Had all the other tests and nothing abnormal was found.But I'm still having the same problems.I had done an oxymeter test and found that I was only getting 79% oxygen to my brain.Then was put on an oxygen concentrator.It worked for a short time but the symptoms came back.So I called the doctor Friday to see if I could quit taking the toprol.They you can't quit cold turkey cause you could have a heart attack.That's scary..And I'm a 44 year old female.I'm not quite ready to go just yet.Especially from quitting a medicine.