THE ECG DIAGNOSIS OF ACUTE MYOCARDIAL-INFARCTION IN THE PRESENCE OF LEFT-BUNDLE-BRANCH BLOCK

The electrocardiographic diagnosis of ischemic heart disease is made m ore difficult in the setting of confounding patterns, including left b undle branch block (LBBB). The electrocardiographic detection of abnor malities arising from acute ischemic cardiac disease in this setting i s possible in certain cases, contrary to popular medical opinion. Seve ral strategies are available to assist in the correct interpretation o f the electrocardiogram (ECG) with LBBB and potential acute ischemia, including: (1) a knowledge of the anticipated ST segment-T wave morpho logies of LBBB and, consequently, the ability to recognize ischemic ch anges; (2) the performance of serial ECGs demonstrating dynamic change ; and (3) a comparison to previous ECGs. The first strategy, an awaren ess of the anticipated ST segment morphologies of LBBB, is the most im portant and not dependent on additional diagnostic testing or past med ical records. Copyright (C) 1998 by W.B. Saunders Company.