– occurs with an average increase in QT interval by approximately 200 ms (a normalQ interval is about 300 ms). The development of multiple reentrant circuits within the heart causes ventricular arrhythmia, or TdP, leading to sudden cardiac death. Drugs causing TdP are considered severe cardiac toxic agents. Several drugs that were removed from the market due to their TdP effect include the cyclooxygenase-2 (COX-2) inhibitors rofecoxib (Vioxx) and valdecoxib (Bextra). o Drug-induced QT prolongation o Hypokalemia o Myocardial ischemic injury o Cardiac hypertrophy o Myocardial fibrosis o Heart failure