Rapid resolution of ST elevation and prediction of clinical outcome in patients undergoing thrombolysis with alteplase (recombinant tissue-type plasminogen activator): results of the Israeli Study of Early Intervention in Myocardial Infarction

Heart attacks (myocardial infarction) occur when ischemia (decrease in oxygen supply due to reduced or no blood flow) is so severe that a portion of the heart muscle can not function and may die. Heart attacks may be precipitated by the lodging or formation of a clot in a coronary artery. A relatively novel therapeutic approach has been to give thrombolytic (clot-breaking) agents that disrupt the clot and restore blood flow. However, thrombolytic therapy is not successful in a number of heart attack patients, who may need emergency treatment if they are to survive. To improve survival of patients with myocardial infarction, it is important to determine which patients are most likely to be responsive to thrombolytic therapy. Electrocardiogram provides an indication of heart function during each heartbeat, and elevation of the ST segment of the electrocardiogram has generally been regarded as an indicator of heart ischemia. However, some studies have suggested that ST elevation is not sensitive enough to detect restoration of coronary artery flow following a heart attack. The usefulness of ST elevation and other indicators of heart function were evaluated in 286 heart attack patients treated with alteplase, a thrombolytic agent. Alteplase was given within four hours of symptom onset, the period when thrombolytic therapy is most likely to be effective. ST elevation diminished quickly in 189 patients, but persisted in 97 patients. Rapid resolution of ST elevation was significantly associated with a good medical outcome; the group in which this occurred had a better initial medical status. However, early reperfusion was independent of this factor and correlated significantly with better heart function and a lower rate of illness and death. Although angiography was used to determine if reperfusion of coronary arteries occurred, correction of ST segment elevation was a better predictor of medical outcome. Rapid resolution of pain was not associated with persistent elevation or normalization of ST segment. Resolution of ST elevation may also reflect the contribution of other factors important to survival of heart tissue, as well as reperfusion. The results also indicate that high-risk patients, such as those with congestive heart failure, may require additional therapy, in spite of resolution of ST elevation. (Consumer Summary produced by Reliance Medical Information, Inc.)