Usefulness of three additional electrocardiographic chest leads (V7, V8, and V9) in the diagnosis of acute myocardial infarction.

Additional electrocardiocardiographic chest leads (V7, V8, and V9) were used in 117 persons consecutively admitted to a coronary care unit. Among the 46 (39%) with a proven acute myocardial infarction the electrocardiograms (ECGs) of 9 (20%) showed ST-segment elevation or abnormal Q-waves, or both, in the three additional leads. In six of the nine, such changes were associated with signs of anterolateral or inferior wall infarction (in three each) on the standard 12-lead ECG, but in the other three (7% of the 46) electrocardiographic changes diagnostic of acute myocardial infarction were found only on the additional chest leads; the last three had characteristic changes in serum enzyme concentrations. This study showed that additional chest leads are helpful in detecting myocardial injury of necrosis in areas of the heart not properly reflected on the standard 12-lead ECG.