Anterior ST segment depression during acute inferior myocardial infarction: evidence for the reciprocal change theory.

We evaluated the recently proposed concern that ECG anterior ST segment depression in patients with acute inferior wall myocardial infarction represents an additional area of ischemia and therefore implies worsened prognosis. We studied patients enrolled in the Aspirin Myocardial Infarction Study (AMIS), ages 30 to 69 years, who sustained an inferior myocardial infarction within 6 months from the start of the study. Two hundred nineteen patients who met those criteria were followed for an average of 38.2 months. One hundred ten patients had significant anterior lead ST depression (greater than or equal to 0.1 mV) during their acute inferior infarction and their 3-year mortality rate was 9.1%. One hundred nine patients had no anterior ST abnormality and a mortality rate of 10.1% (p = ns). Only one patient with significant depression had a subsequent anterior wall myocardial infarction. Anterior ST depression correlated closely with the magnitude of inferior ST segment elevation. Since ST depression does not alter long-term mortality but relates to magnitude of ST elevation, it probably represents a reciprocal change.