BRIEF REPORTS Polymorphous Ventricular Tachycardia Early After Acute Myocardial Infarction Yochai Birnbaum, MD, Samuel Sclarovsky, MD, Ronen Ben-Ami, MD, Eldad Rechavia, MD, Boris Strasberg, MD, Jairo Kusniec, MD, Aviv Mager, MD, and Jaqueline Sulkes, MSc V entricular tachyarrhythmias are a major cause of car- diac death within the early hours of an evolving acute myocardial infarction. Diverse cytochemical and metabolic alterations develop in the ischemic and peri- ischemic zones after coronary artery occlusion and subsequent reperfusion. 1,2 These alterations change rapidly over time and may cause various morphologi- cally distinct ventricular arrhythmias in the different stages of an acute myocardial infarction.1~3 One type of malignant ventricular tachyarrhythmia that appears dur- ing an acute myocardial infarction is polymorphous ven- tricular tachycardia (VT). 3,4 The electrophysiologic mechanism and the therapy differ from those of other forms of vT.5~~ The occurrence of polymorphous VT in the early stages of an acute myocardial infarction has been infrequently reported,4 although an incidence of 1.2 to 2% during overall hospitalization for acute myocar- dial infarction had been reported.4 This report describes the clinical and electrocardiographic features of patients with polymorphous VT in the early stages of an evolv- ing acute myocardial infarction. Data for this study were collected retrospectively from patients admitted to the coronary care unit from January 1989 to August 1991 with an evolving acute myocardial infarction. The criteria for the diagnosis of an acute myocardial infarction were: severe chest pain of >30 minutes duration, characteristic evolutionary electrocardiographic changes and a typical elevation of serum creatine kinase. All patients had a continuous 3- lead electrocardiographic recording for 2 to 4 hours after admission, using 3 leads simultaneously that demonstrated maximal ST elevations. Of 954 patients, admitted during that period, 7 patients had polymor- phous VT documented within the first 4 hours after ad- mission. Of the 954 patients, 402 received intravenous thrombolytic therapy (42%). The following data were recorded: age, sex, previ- ous history of coronary artery disease, Killip function- al class on admission, and the time that elapsed from the onset of cardiac symptoms and from the initiation of thrombolytic therapy to the onset of ventricular ar- rhythmia. Serum potassium and calcium levels on ad- mission were noted. Normal values for our laboratory are: potassium, 3.5 to 5.0 mmollliter, calcium, 2.12 to 2.62 mmollliter. Medication taken before polymorphous VT and therapy for arrhythmia were recorded. The heart rate, rhythm and the QT interval were determined using the last complexes before the onset of the ar- From the Department of Cardiology, and the Epidemiology Unit, Bei- linson Medical Center, and the Tel Aviv University Sackler School of Medicine, Petah Tikva, Israel 49100. Manuscript received July 20, 1992; revised manuscript received September 11, 1992, and accepted September 13. rhythmia. The corrected QT (QTc) was calculated ac- cording to Bazett’s formula. The QT and QTc intervals were de$ned as prolonged if they exceeded 440 and 460 ms, respectively. The magnitude of ST elevation wa,s measured to the nearest 0.5 mm, 0.06 second after the J point in the lead with the maximal ST elevation. ST elevation was determined 3 minutes and 1 minute be- fore the arrhythmia, in the last complexes before the ar- rhythmia, and 1,2,5 and 10 minutes, respectively, after termination of the ventricular arrhythmia. The electro- cardiographic pattern before the appearance of poly- morphous VT was classified according to the definition mentioned later. To determine the incidence of the dif ferent electrocardiographic patterns of ischemia during acute myocardial infarction, we examined the patterns in a sample of 255 consecutive patients with an evolv- ing acute myocardial infarction, admitted within 6 hours from the onset of cardiac symptoms, before in- version of the T waves or development of new patho- logic Q waves occurred (patients with a cardiomy- RGURE 1. The electrocardiographic p&terns Examples of the different patterns are demonstrated in 3 different patients with anterior acute myocardial infarction. Pattern A q tall peaked positive 1 waves in the involved leads (V:, to V& without ST elevation or major changes in the terminal portion of the QRS complex; Pattern B = positive T waves, ST elevation (so.1 mv) in leads V2 to V6, without mqjor changes in the terminal portion of the QRS; Pattern C q positive 1 waves, ST elevation (SO.1 mv), accompanied by distortion of the terminal portion of the QRS complex (dk4 appearance of the S wave in leads VI to V3, emergence a# the J point at a level above the lower half of the R wave in leads v4 to v4). BRIEF REPORTS 1’45