Are your magnesium and potassium levels normalized? Check the insert for the current BP medication as it may be potassium sparing. As you go off of it, your potassium blood levels may plummet, giving rise the to the irregularity.
Otherwise, boosting your magnesium and potassium levels may support regular heart rate during withdrawal. I often have my patients taper very slowly.
Discuss this situation with a local physician to avoid complications.