Application of STREAM trial in management of acute myocardial infarction in real world practice

Abstract

Primary PCI has been consistently superior to thrombolytic therapy within 3 h of onset of ST-segment elevation myocardial infarction (STEMI). However, primary PCI is beset with several problems. There is issue of lack of availability of cath lab enabled centers with huge delays in transfers of these patients to such centers. This issue is especially relevant in developing countries with limited accessibility to cath labs. Further, there is an issue of off-hours emergency PCI which seems to have a worse outcome than daytime procedures. Last but not the least, many physicians feel rushed with need to do primary PCI and would love to get some breathing space to consider other options, such as CABG and medical therapy. Facilitated PCI (PCI after thrombolysis) was supposed to address several of these issues particularly time delays with PCI but the results from several trials were rather disappointing (particularly related to high bleeding risks with this approach).1 On the other hand, pharmacoinvasive PCI is a strategy wherein patients are transferred to the major PCI center without the decision being made for automatic immediate PCI on arrival. TRANSFER AMI trial showed that this kind of therapy (dual thrombolytic and PVI strategy) could be effective and bleeding risks significantly reduced if PCI was performed at least 3 h after administration of thrombolysis.2 In the current article on the Strategic Reperfusion Early after Myocardial Infarction (STREAM) study, Armstrong et al describe a strategy of pre-hospital thrombolysis coupled with coronary angiography and primary PCI in patients with STEMI who presented within 3 h after symptom onset and who could not undergo PCI within 1 h after the first medical contact.3 They demonstrate that this strategy is at least as effective as that undertaking primary PCI on arrival to a cath lab enabled center (without thrombolysis). When patients on tenecteplase reached a major medical center, 36% needed urgent PCI (decided by lack of ST resolution on ECG) and received it just over 2 h after randomization. The other 64% of patients did not need urgent PCI and received an angiogram in an average of 17 h after arrival and, based on the results, received PCI or CABG under elective circumstances. This gave more time to plan an elective procedure and also consider other options. PCI at some point was performed in 90% of the PCI group vs. 80% of the thrombolysis group. CABG was performed in more patients in the thrombolysis group (4.7% vs. 2.1%). The primary endpoint (a composite of all-cause mortality, shock, congestive heart failure, and subsequent heart attack at 30 days) occurred in 12.4% in the thrombolysis group vs. 14.3% in the primary PCI group (relative risk in the thrombolysis group, 0.86; 95% confidence interval, 0.68–1.09; p = 0.21). The end-point reduction in the pharmacoinvasive group was driven largely by heart failure and shock, and it also enabled more patients to get bypass surgery, which might impact long-term mortality. Another interesting finding was that patients with inferior MIs seemed to do better in the pharmacoinvasive arm, which perhaps is reflective of the fact that lytic therapy is more efficacious in recanalizing the right than the left coronary artery. The only downside of pharmacoinvasive arm was rate of intracranial bleeding in the thrombolysis group was five times that in the primary PCI group (1.0% vs. 0.2%, p = 0.04). This fact was apparent early on the trial and led to a reduction in the dose of tenecteplase in elderly. After that amendment, which was made after 20% of planned recruitment, these rates declined to (0.5% vs. 0.3%), respectively, after the protocol amendment, with no difference in stroke rates. The conclusion of Armstrong and colleagues is controversial, since there was a similar risk of the primary end point in the two study groups and a significantly higher risk of intracranial bleeding with early thrombolysis. Thus primary PCI remains the treatment of choice in such patients who have close access to cath lab centers. However, there may be a cost advantage with the avoidance of an urgent invasive procedure in about two-thirds of these patients which may offset the extra cost of the thrombolytic agent. Less shock and heart failure in the thrombolysis group, coupled with the promising long-term outcomes reported in studies of pharmaco-invasive therapy reported previously certainly indicates that pharmacoinvasive therapy may provide a useful and reasonable option for many patients who cannot undergo timely PCI. It is especially useful in situations where PCI related delays such as occur in real-world situations, a greater clinical benefit would be anticipated for early pharmacoinvasive therapy. Major delays are prevalent in remote and urban regions. Further, although primary PCI in patients with STEMI is preferred, it is often unachievable.