Importance of posterior chest leads in patients with suspected myocardial infarction, but nondiagnostic, routine 12-lead electrocardiogram

Criteria for reperfusion therapy in acute myocardial infarction require the presence of ST elevation in 2 contiguous leads. However, many patients wit h myocardial infarction do not show these changes on a routine 12-lead elec trocardiogram and hence are denied reperfusion therapy. Posterior chest lea ds (V-7 to V-9) were recorded in 58 patients with clinically suspected myoc ardial infarction, but nondiagnostic routine electrocardiogram. ST elevatio n >0.1 mV or Q waves in greater than or equal to 2 posterior chest leads we re considered to be diagnostic of posterior myocardial infarction. Eighteen patients had these changes of posterior myocardial infarction, All 18 pati ents were confirmed to have myocardial infarction by creatine phosphokinase criteria or cardiac catheterization. Of the 17 patients who had cardiac ca theterization, 16 had left circumflex as the culprit vessel. We conclude th at posterior chest leads should be routinely recorded in patients with susp ected myocardial infarction and nondiagnostic, routine electrocardiogram. T his simple bedside technique may help proper treatment of some of these pat ients now classified as having unstable angina or non-Q-wave myocardial inf arction, (C)1999 by Excerpta Medica, Inc.