The risk factors of acquired long QT syndrome (aLQTS) are sometimes overlooked in clinics. Drugs, hypokalemia, age and female sex are well-known risk factors of QT prolongation-dependent torsade de pointes (TdP), which explains the high incidence of sudden cardiac death in LQT patients. Here, we report a case of an elderly female patient with lung cancer who was in poor condition, for whom amiodarone was mistakenly prescribed to rectify premature ventricular contractions. QT prolongation-dependent TdP immediately followed intravenous injection of amiodarone. Fortunately, the patient survived aborted sudden cardiac arrest after effective cardio-pulmonary resuscitation and electric defibrillation. Upon reviewing the clinical information, several pre-existing risk factors of aLQTS and TdP were identified. The mistaken prescription of amiodarone provoked TdP after these risk factors were overlooked in this case and thus predisposed this patient to a high susceptibility of drug-induced TdP.