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Combined reperfusion strategies in ST-segment elevation MI: Rationale and current role

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ABSTRACTPrimary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy for ST-elevation myocardial infarction (MI), but most patients do not arrive at a PCI facility within the recommended 90 minutes of first medical contact. If delay is expected, timely thrombolysis is recommended, followed by early transfer for PCI. The authors review the rationale behind three combined reperfusion strategies—facilitated PCI, pharmacoinvasive therapy, and rescue PCI—and data on their effectiveness.

KEY POINTS

  • When the expected door-to-balloon time is less than 90 minutes and the door-to-balloon time minus the door-to-needle time is less than 60 minutes, the preferred approach is PCI not preceded by thrombolysis.
  • Evidence suggests that routine early (but not immediate) PCI—ie, 2 to 6 hours after thrombolysis—is beneficial, particularly in patients with high-risk ST-elevation MI.
  • Hospitals and emergency services should participate in community-based and regional systems of care, with standardized protocols to ensure expeditious transfer and prompt reperfusion.
  • Prehospital thrombolysis followed by early transfer to a PCI facility as part of a community-based system of care may further improve outcomes of patients with very long transfer times.


 

References

Effective and rapid reperfusion is crucial in patients with acute ST-segment elevation myocardial infarction (MI). The preferred strategy for reperfusion—when it can be performed in a timely fashion at an experienced facility—is primary percutaneous coronary intervention (PCI), which produces outcomes superior to those of pharmacologic thrombolysis. 1

See related editorial

Unfortunately, in the United States about half of patients present to hospitals that do not have PCI capability, 2 and in one analysis, 91% of transferred patients had a door-to-balloon time greater than the recommended 90 minutes, with a mean of 152 minutes. 3 (In this case, the door-to-balloon time was the time that elapsed between entry into the first hospital and inflation of the PCI balloon at the second hospital.)

In situations such as these, a combined approach may be appropriate, with thrombolysis delivered by paramedics or at a local facility, followed by transfer to a PCI facility and performance of PCI within a few hours. However, this is feasible only if standardized community-based or regional protocols for prompt transfer and reperfusion are in place.

In this paper we discuss the rationale and the clinical data behind several approaches to combined reperfusion, as well as experiences with community-based care protocols.

WITHIN 3 HOURS OF SYMPTOM ONSET, THROMBOLYSIS IS AS GOOD AS PCI

The PRAGUE-2 Trial

In the randomized PRAGUE-2 trial, 4 patients with ST-elevation MI who presented to a non-PCI facility had better outcomes if they were transferred promptly for PCI (median door-to-balloon time 97 minutes), as opposed to receiving local therapy with streptokinase. However, for patients presenting within 3 hours of symptom onset, the mortality rates were comparable with either strategy. 4

See the glossary of clinical trial names below

The CAPTIM trial

In the CAPTIM trial, 5 patients who presented within 2 hours of symptom onset and who were randomized to receive prehospital thrombolysis had outcomes similar to those of patients treated with primary PCI, despite a short door-to-balloon time (82 minutes).

The Vienna STEMI Registry

In the Vienna STEMI Registry, 6 the mortality rates with primary PCI and with thrombolysis were similar when patients presented within 2 hours of symptom onset. However, as the time from symptom onset increased, primary PCI appeared to offer an increasing survival benefit compared with thrombolysis.

Comments: Thrombolysis is effective mostly in the first 2 to 3 hours, with some benefit up to 12 hours

Previous studies have shown that the sooner thrombolysis is given after symptom onset, the more effective it is. If it is given within an hour of symptom onset, the relative reduction in the mortality rate is 50% and the absolute reduction is 6.5% compared with no reperfusion therapy. If it is started in the second hour, the absolute reduction in the mortality rate drops to 4%, and a lesser benefit extends to patients presenting up to 12 hours after symptom onset. 7 This time-dependent benefit is due to the fact that very early reperfusion of the occluded coronary artery may lead to full recovery of ischemic tissue and thus prevent necrosis. In addition, thrombolysis in the first 2 hours is highly efficacious in lysing a fresh thrombus.

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