I am a 63 year old female about 20 lbs overweight but in good health. I had an a-fib attack in 1996 and had to be hospitalized but was converted through medication. I had a 2nd attack in 2000 and again was converted in the ER with medication and sent home. I recently has my 3rd a-fib attack while on vacation and spent 2 days in the hospital. I am on Toprol XL 100 mg. and a blood thinner. I exercise regularly. I recently started taking Magnesium supplements (oral) - 400 mg. a day and started having skipped heartbeats. I also have Mitral Valve Prolapse. I am also under a tremendous amount of stress with family and work responsibilities. Can Magnesium cause PVC s?