[Correlations between the efficacy of thrombolytic therapy and appearance of abnormal Q waves in the early stages of acute myocardial infarction].

BACKGROUND

The purpose of this study was to determine the time course of the appearance of abnormal Q waves on the electrocardiogram (ECG) over the first 6 hrs of the symptoms of acute myocardial infarction (AMI) and to determine what implications, if any, such Q waves have for the efficacy of thrombolytic therapy. Severe myocardial ischemia can produce early QRS changes in the absence of infarction. Abnormal Q waves on the baseline ECG may not be an accurate marker or irreversibly injured myocardium.

METHODS

A study of 232 patients with AMI consecutively admitted to our coronary care units was carried out. Patients with previous AMI were not included. The presence and number of abnormal Q waves, as defined by Selvester, on the initial ECG was determined for each patient. The presence or absence and magnitude of ST segment elevation and depression were recorded and these data were used to estimate the left ventricular infarct size should thrombolytic therapy not be given (Aldrich score). Quantitative thallium-201 tomographic imaging was performed after a mean of 42 +/- 40 days from hospital discharge in 145 patients.

RESULTS

In patients admitted within 1 hr of symptoms, 53% had abnormal Q waves on the initial ECG independent of the duration of symptoms before therapy (p < 0.001). Despite this finding, the presence of abnormal Q waves on the admission ECG did not eliminate the effect of thrombolytic therapy on reducing final infarct size (p < 0.001).

CONCLUSIONS

Abnormal Q waves are a common finding early in the course of AMI. However, there is no evidence that abnormal Q waves are associated with less benefit in terms of reduction of infarct size after thrombolytic therapy.