The safety and efficacy of systemic salvage thrombolysis in acute myocardial infarct

BACKGROUND: Thrombolysis reduces mortality in patients with acute myocardial infarction hospitalized within 6 hours of the symptom onset. Infarctions involving a small area of the myocardium show a lower mortality in comparison to those involving a large area. The aim of this study was to evaluate the safety and efficacy of rescue thrombolysis in patients with large acute myocardial infarction who had failed standard thrombolysis. METHODS: From January 1995 to December 1997, ninety patients (69 males, 21 females, mean age 56.7 +/- 9 years), hospitalized for suspected acute myocardial infarction within 4 hours of the symptom onset, suitable for thrombolysis (first episode), and who experienced pain and showed persistent ST segment elevation 120 min after starting thrombolysis, were randomized (single blind) into two groups: Group A (n = 45) received an additional thrombolytic treatment (rt-PA 50 mg), 10 mg as a bolus plus 40 mg in 60 min; Group B (n = 45) received conventional therapy. Positive non-invasive markers were defined as follows: resolution of chest pain; > 50% reduction in ST segment elevation; double marker of creatine phosphokinase (CPK) and CK-MB activity 2 hours after the start of thrombolysis; occurrence of reperfusion arrhythmias within the first 120 min of thrombolytic therapy. Blood pressure, heart rate and ECG were continuously monitored. Echocardiogram was carried out at entry and before discharge to control ejection fraction and segmental wall motion. Adverse events such as death, reinfarction, recurrent angina, incidence of major and minor bleeding, and emergency bypass surgery or coronary angioplasty were checked. RESULTS: Thirty-five patients (77.7%) showed reperfusion (10-50 min) after the start of additional rt-PA. In patients who did not receive additional thrombolysis, only 12 (26.6%) showed reperfusion 65-115 min after the end of rt-PA infusion. Group A showed an earlier and lower CK and CK-MB peak than Group B (p = 0.0001, p = 0.009, and p = 0.002, respectively). Mortality (n = 16, 17.7%) was higher in Group B (n = 13) than in Group A (n = 3) (28.8 vs 6.6%, p = 0.041). Seven patients from Group A showed non-fatal reinfarction. Angina was observed in 18 (40%) patients from Group A and 3 (6.6%) from Group B (p = 0.006). Ten of these patients underwent urgent coronary angioplasty (9 from Group A and 1 from Group B) and 3 from Group A urgent bypass surgery. Minor bleeding was higher in Group A than in Group B (44.4 vs 15.5%, p = 0.047). A major bleeding was observed in Group A (non-fatal stroke). At predischarge echocardiogram ejection fraction was higher in Group A than in Group B (46 +/- 8 vs 38 +/- 7%, p = 0.0001). CONCLUSIONS: Our data suggest that an additional dose of a thrombolytic drug in patients with unsuccessful thrombolysis is feasible, and the bleeding increase is an acceptable risk in comparison with the advantages obtained from a reduced infarct extension. Rescue thrombolysis could save time and allow mechanical revascularization to be carried out in patients admitted to a hospital without interventional cardiology laboratory or in those who have to be refereed to other hospitals for urgent bypass surgery.