Q-wave evolution of a first acute myocardial infarction without significant ST segment elevation

Background: Some patients with acute myocardial infarction presenting witho ut significant ST segment elevation develop a Q-wave infarction. It is uncl ear whether these patients can be identified from the admission electrocard iogram (ECG) and whether they differ in their in-hospital prognosis from th ose who retain a non-Q-wave myocardial infarction. Methods: In 432 consecut ive patients admitted to our centre with a first acute myocardial infarctio n without Q waves and with ST segment amplitudes less than or equal to0.1 m V on admission, we assessed the frequency, the electrocardiographic predict ors and the short-term implications of a Q-wave evolution. Results: In 94 p atients (22%), a Q-wave myocardial infarction evolved before hospital disch arge (14 anterior, 26 inferior, six lateral, and 48 posterior). Minor anter ior ST segment elevation was 36% sensitive and 95% specific in predicting a nterior Q waves; minor inferior ST segment elevation; 42% and 89%, respecti vely, for inferior Q waves; and a maximal ST segment depression greater tha n or equal to0.2 mV in leads V-2-V-3 with upright T waves and without remot e ST segment depression, 38% and 97%, respectively, for posterior R waves. Although patients with a Q-wave evolution had a greater creatinkinase MB pe ak than those retaining a non-Q-wave pattern (191+/-113 vs. 105+/-77 IU/1, respectively, P<0.001), they experienced a benign in-hospital course, with similar risk of severe complications after adjustment for the baseline clin ical predictors than non-Q-wave patients. Conclusions: About one fifth of p atients with a first acute myocardial infarction without a significant ST s egment elevation develop a Q-wave infarction and the admission ECG can help identify them. This evolution, however, is not associated with a worse in- hospital outcome. (C) 2001 Elsevier Science ireland Ltd. All rights reserve d.