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Acute coronary artery obstruction in myocardial infarction: overview of thrombolytic therapy
Insights
Early thrombolytic therapy using streptokinase significantly reduces infarct size, improves heart function, and lowers mortality in acute myocardial infarction patients. This treatment is most effective when administered within 2 hours of symptom onset.
Area of Science:
- Cardiology
- Cardiovascular Medicine
- Interventional Cardiology
Background:
- Pump failure is the leading cause of cardiac death.
- Current temporary mechanical or pharmacologic support for the heart has limited success.
- Focus is shifting towards preventing ventricular failure and limiting myocardial infarct size, including early reperfusion strategies.
Purpose of the Study:
- To evaluate the effects of early thrombolytic therapy in acute myocardial infarction.
- To assess the impact on enzymatic infarct size, left ventricular function, and early mortality.
- To compare intracoronary streptokinase with conventional treatment.
Main Methods:
- A randomized trial involving 533 patients admitted within 4 hours of acute myocardial infarction symptom onset.
- Comparison of early thrombolytic therapy (intracoronary streptokinase or intravenous followed by intracoronary streptokinase) with conventional treatment.
- Assessment of infarct size (cumulative alpha-hydroxybutyrate dehydrogenase release), left ventricular ejection fraction (radionuclide angiography), and 12-month mortality.
Main Results:
- Thrombolytic therapy significantly reduced enzymatic infarct size (median 760 vs. 1,179 U/liter, p=0.0001).
- Left ventricular ejection fraction was higher in the thrombolytic group (median 50% vs. 43%, p=0.0001).
- Twelve-month mortality was lower with thrombolytic therapy (8% vs. 16%, p<0.01).
- Benefits were most pronounced in patients treated within 2 hours or with ST-segment elevation ≥1.2 mV.
Conclusions:
- Early thrombolytic therapy with streptokinase is effective in reducing infarct size, improving left ventricular function, and decreasing mortality in acute myocardial infarction.
- Treatment timing and electrocardiographic findings (ST-segment elevation) are critical predictors of thrombolysis benefit.
- Further research may focus on optimizing patient selection and treatment protocols for thrombolytic therapy.
Abstract:
Pump failure, ranging from ventricular dysfunction to acute cardiogenic shock, is now the leading cause of cardiac death. Efforts at temporary mechanical or pharmacologic support of the heart have been largely unsuccessful so that attention is now directed toward prevention of ventricular failure and limitation of myocardial infarct size or even outright prevention of infarction itself. In particular, attention has been refocused on earlier reperfusion efforts with streptokinase. 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 (Netherlands Interuniversity Cardiology Institute). 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 hours after onset of symptoms indicative of acute myocardial infarction. Of the patients eligible for this detailed analysis, 245 were allocated to thrombolytic therapy and 243 to conventional treatment. Early angiography was preformed in 212 of the 245 patients allocated to thrombolytic therapy. Patency of the infarct-related artery was achieved in 181 patients (85%). Enzymatic infarct size, measured from cumulative alpha-hydroxybutyrate dehydrogenase release, was smaller in patients allocated to thrombolytic therapy (median 760 versus 1,179 U/liter in control subjects, p = 0.0001). Left ventricular ejection fraction measured by radionuclide angiography before discharge was higher after thrombolytic therapy (median 50% versus 43% in control subjects, p = 0.0001). Twelve month mortality was lower in patients allocated to thrombolytic therapy (8% versus 16% in the control group, p less than 0.01). In multivariate regression analysis infarct size limitation, improvement of left ventricular ejection fraction and 3 month mortality were predicted by sigma ST, time from onset of symptoms to admission and Killip class at admission. Thrombolysis was most useful in patients admitted within 2 hours after onset of symptoms and in patients with a sigma ST segment 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 sigma ST less than 1.2 mV, admitted 2 to 4 hours after onset of symptoms.