Cardiotoxicity is a major adverse effect of drugs and has led to a number of withdrawals, for example terfenadine (withdrawn due to arrhythmia) and cisapride (sudden cardiac death and arrhythmia), and more recently for sibutramine (myocardial infarction).  It also caused restrictions to be placed on some drugs (such as thioridazine), delays in regulatory approval, and late-stage compound failures.  According to Drug Discovery World¹, drugs causing cardiotoxicity (such as heart damage and arrhythmia) have caused 28% of drug withdrawals in the United States over the past 30 years.