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Which patients benefit most from early thrombolytic therapy with intracoronary streptokinase?
Insights
Early thrombolytic therapy significantly reduces enzymatic infarct size, improves left ventricular function, and lowers mortality in acute myocardial infarction patients. These benefits are most pronounced when treatment is initiated within 2 hours of symptom onset.
Area of Science:
- Cardiology
- Emergency Medicine
- Pharmacology
Background:
- Acute myocardial infarction (AMI) is a leading cause of mortality.
- Early reperfusion therapy is crucial for improving outcomes in AMI.
- The efficacy of thrombolytic therapy in AMI requires further investigation.
Purpose of the Study:
- To evaluate the impact of early thrombolytic therapy on enzymatic infarct size.
- To assess the effect of thrombolysis on left ventricular function post-AMI.
- To determine the influence of thrombolytic therapy on early mortality in patients with AMI.
Main Methods:
- A randomized trial comparing intracoronary streptokinase (alone or preceded by IV streptokinase) with conventional treatment.
- Analysis of 488 patients admitted within 4 hours of AMI symptom onset.
- Assessment of enzymatic infarct size, left ventricular ejection fraction, and 3-month mortality.
Main Results:
- Thrombolytic therapy significantly reduced enzymatic infarct size (p = .0001).
- Left ventricular ejection fraction was significantly higher in the thrombolysis group (p = .0001).
- Three-month mortality was significantly lower with thrombolytic therapy (6% vs. 14%, p = .006).
Conclusions:
- Early thrombolytic therapy is effective in limiting infarct size, preserving left ventricular function, and reducing mortality in AMI.
- Treatment initiated within 2 hours of symptom onset and with ST elevation ≥ 1.2 mV showed the greatest benefit.
- No significant benefits were observed in patients treated between 2-4 hours with ST elevation < 1.2 mV.
Abstract:
The effect of thrombolysis in acute myocardial infarction on enzymatic infarct size, left ventricular function, and early mortality was studied in subsets of patients in a randomized trial. Early thrombolytic therapy with intracoronary streptokinase (152 patients) or with intracoronary streptokinase preceded by intravenous streptokinase (117 patients) was compared with conventional treatment (264 patients). All 533 patients were admitted to the coronary care unit within 4 hr after onset of symptoms indicative of acute myocardial infarction. Four hundred eighty-eight patients were eligible for this detailed analysis, and 245 of these were allocated to thrombolytic therapy and 243 to conventional treatment. Early angiographic examinations were performed in 212 patients allocated to thrombolytic therapy. Patency of the infarct-related artery was achieved in 181 patients (85%). Enzymatic infarct size, as measured from cumulative alpha-hydroxybutyrate dehydrogenase release, was smaller in patients allocated to thrombolytic therapy (median 760 vs 1170 U/liter in control patients, p = .0001). Left ventricular ejection fraction measured by radionuclide angiography before discharge from the hospital was higher after thrombolytic therapy (median 50% vs 43% in control patients, p = .0001). Three month mortality was lower in patients allocated to thrombolytic therapy (6% vs 14% in the control group, p = .006). With the use of multivariate regression analysis, infarct size limitation, improvement in left ventricular ejection fraction, and three month mortality were predicted by sum of the ST segment elevation, time from onset of symptoms to admission, and Killip class at admission. Thrombolysis was most effective in patients admitted within 2 hr after onset of symptoms and in patients with a sum of ST segment elevation of 1.2 mV or more. On the other hand, no beneficial effects of streptokinase on enzymatic infarct size, left ventricular function, or mortality were observed in the subset of patients with a sum of ST segment elevation of less than 1.2 mV who were admitted between 2 and 4 hr after onset of symptoms.