67-year-old woman with thrombocytopenia (treated with prednisolon and azathiopryn) was admitted because of acute myocardial infarction without ST segment elevation (NSTEMI). From the 2nd day we observed increasing QTc interval from 461 ms with normal potassium level. Suddenly on the 6th day of the so far uncomplicated AMI ventricular fibrillation developed and was successfully treated with DC shock, and amiodarone (150 mg i.v.) was administered because of recurrent NSVT. Potassium level was 2.9 mmol/l. Within the next 2 days in the morning hours we observed episodes of recurrent polymorphic ventricular tachycardia (PMVT), always progressing into ventricular fibrillation (VF). The ECG showed QT interval--520 ms, QTc--602 ms. The patient was given an increasing dose of beta-blocker and lidokaine in i.v. infusion. After this regimen PMVT/VF did not recur and QT was normalized. Additionally successful PCI of LAD with 80% stenosis was performed. The paper discusses the problem of PMVT in the settings of AMI.