[Are ECG criteria for indications for thrombolysis in acute myocardial infarct defined too narrowly?].

BACKGROUND

Despite the advantages of fibrinolytic therapy in acute myocardial infarction only about 20% of these patients receive this therapy. We studied patients excluded from fibrinolysis to identify subgroups with high mortality, which could derive benefit from more liberal interpretation of the indications for fibrinolytic therapy.

METHODS

Retrospective chart review to identify patients with acute myocardial infarction in our coronary care unit 7/88-7/89. All patients received a questionnaire one year after this myocardial infarction. Patients not answering the questionnaire were contacted by phone or the information was sought from their physician. Indications for thrombolysis (with streptokinase or rTPA) were ST elevations of greater than or equal to 2 mm in greater than 2 adjacent leads and the absence of contraindications.

RESULTS

In 231/242 (95%) of the identified patients a complete follow-up was obtained, 32% were age greater than 70 years, 30% were admitted greater than 6 h after the beginning of the symptoms, 64% did not fulfil the ECG criteria for thrombolysis, 21% (49/231) received thrombolytic therapy. The mortality after one year was 20.3% in patients not treated with thrombolysis and 8.2% in patients with thrombolysis (difference 12.1%, 95% confidence interval 2.9-21.3%, p = 0.048). Patients with preceding old infarctions (n = 58) fulfilled the ECG criteria for thrombolysis in a significantly smaller proportion (21% vs 41%, p = 0.004). Of all patients 12% were excluded from thrombolytic therapy due to a negative initial ECG and yet developed a Q ware infarction. The one year mortality of patients not given thrombolysis and with a Q wave infarction was 24% (22/93, p = 0.02 as compared to patients with thrombolysis), in patients with non Q wave infarction it was 13% (11/82, p = 0.41) and in patients with ambiguous ECG it was 57% (4/7, p = 0.006). The mortality in patients with a preceding infarction was 31% and significantly higher than in patients with a first infarction (16%, p = 0.049) and in patients receiving thrombolysis (8.2%, p = 0.005).

CONCLUSIONS

By excluding patients with acute myocardial infarction from thrombolytic therapy a group with high first year mortality is selected. Most patients are excluded because of an initial ECG not showing enough ischemia to fulfil the criteria for thrombolytic therapy. A prospective study of thrombolytic therapy using less rigid ECG criteria in the subgroups with the highest mortality (patients with preceding myocardial infarction or ambiguous ECG) seems necessary.