Primary angioplasty or thrombolysis for acute myocardial infarction?

Results from clinical trials on ST‐elevation myocardial infarction in a historic perspective with some pathophysiological aspects

OBJECTIVE

Since the publication of the large trials on streptokinase and aspirin improving mortality related to an acute ST-elevation myocardial infarction (STEMI) there has been numerous studies on improving treatment results with new fibrinolytics, adjuvant heparin therapy and primary percutaneous intervention (PCI). The aim of the present overview is, in a historic perspective, to link some of the pathophysiology of mechanisms related to plaque rupture and following thrombosis to the effects of drug combinations and PCI observed in major clinical trials conducted in patients with STEMI.

DESIGN

The overview comprises short analyses of the initial streptokinase trials (GISSI-1 and ISIS-2), the comparisons between streptokinase and tissue plasminogen activator (rt-PA) and the role of adjuvant heparin treatment (GISSI-2, ISIS-3, GUSTO I). Also included is the comparison between the new bolus-teplases and traditional, accelerated infusion of rt-PA (GUSTO III and ASSENT-2) and between unfractionated heparin (UFH) and low molecular weight heparin (LWMH) given in addition to tenecteplase (ASSENT-3). The pathophysiology of the antiplatelet and antithrombin effects is described, in order to elucidate the treatment differences observed in the trials. In addition, the role of primary PCI is discussed in view of the results in a recent meta-analysis of controlled comparisons with fibrinolytic therapy.

RESULTS

Based upon these trials it seems that the optimal thrombolytic treatment is a combination of a bolus-teplase (tenecteplae) and LMWH given on top of aspirin. Primary PCI may be the most optimal treatment, provided given early following STEMI (<1 h), but whether PCI is the best alternative for all patients with STEMI is still a matter of debate.

CONCLUSION

During the last 15 years the optimal antithrombotic treatment of STEMI has developed from a combination of streptokinase and aspirin to the new bolus-teplases combined with LMWH and aspirin. The use of primary PCI may be a better alternative than fibrinolytic therapy, but such a statement needs confirmation in a large comparison between PCI and a quick infusion of modern fibrinolytic agents.

Review of tenecteplase (TNKase) in the treatment of acute myocardial infarction

TNKase is a genetically engineered variant of the alteplase molecule. Three different mutations result in an increase of the plasma half-life, of the resistance to plasminogen-activator inhibitor 1 and of the thrombolytic potency against platelet-rich thrombi. Among available agents in clinical practice, TNKase is the most fibrin-specific molecule and can be delivered as a single bolus intravenous injection. Several large-scale clinical trials have enrolled more than 27,000 patients with acute myocardial infarction, making the use of this drug truly evidence-based. TNKase is equivalent to front-loaded alteplase in terms of mortality and is the only bolus thrombolytic drug for which this equivalence has been formally demonstrated. TNKase appears more potent than alteplase when symptoms duration lasts more than 4 hours. Also, TNKase significantly reduces the rate of major bleeds and the need for blood transfusions. The efficacy of TNKase may be further improved by enoxaparin substitution for unfractionated heparin, provided that enoxaparin dose adjustment is made for patients more than 75 years old. Hitherto, the small available randomized studies and international clinical registries suggest that pre-hospital TNKase is as effective as primary angioplasty, thus laying the foundations for a new fibrinolytic, TNKase-based strategy as the backbone of reperfusion in acute myocardial infarction.

Percutaneous coronary intervention and 1 year survival in patients treated with fibrinolytic therapy for acute ST-elevation myocardial infarction

AIMS

To assess the predictors of 1 year mortality in patients treated with fibrinolytic therapy for ST-segment elevation myocardial infarction (STEMI) and to determine whether a strategy of early percutaneous coronary intervention (PCI) improves outcome.

METHODS AND RESULTS

Consecutive patients (n = 474) admitted to our unit (1998-2001) with STEMI were treated with fibrinolytic therapy. For each patient, age, gender, admission via mobile coronary care unit (MCCU), infarct location, initial systolic blood pressure and Killip class, prior history of ischaemic heart disease, hypertension, diabetes mellitus, smoking status, family history, hyperlipidaemia, and in-hospital PCI (n = 154) were recorded. Mortality at 1 year was obtained from medical records (n = 473). Binary logistic regression analysis was performed to determine independent predictors of 1 year mortality. Mortality in the non-PCI group was 21 vs. 7% in the PCI group. Independent predictors of 1 year mortality were age (risk ratio 1.12, 95% CI 1.08-1.15, P < 0.0001), initial SBP < or = 80 mmHg (risk ratio 4.34, 95% CI 1.68-11.2, P = 0.002), initial Killip class > or = 3 (risk ratio 2.97, 95% CI 1.42-6.2, P = 0.004), and lack of in-hospital PCI (risk ratio 0.39, 95% CI 0.19-0.81, P = 0.012). Although the PCI group were younger (P = 0.007), more likely to be admitted via the MCCU (P = 0.008), with a shorter pain to needle time (P = 0.04), multivariable analysis adjusted for these differences.

CONCLUSION

In-hospital PCI in patients treated with fibrinolytic therapy for STEMI is associated with a substantial reduction in 1 year mortality.