Immediately after the diagnosis of STEMI, the patients should receive oxygen and adjunct pharmacology based on predetermined, guideline-based, institution-specific protocol, including but not limited to aspirin, clopidogrel/prasugrel, statin, and possibly glycoprotein IIb/IIIa (GP IIb/IIIa) inhibitor. All patients should be placed on a cardiac monitor with a defibrillator on standby.
MODE OF REPERFUSION
The current ACC/AHA guidelines for the treatment of STEMI recommend that a reperfusion strategy, based on either pharmacological management with a fibrinolytic agent or mechanical management with primary PCI, should be implemented as soon as possible after arrival in the ED (class I-A recommendation).7
Factors affecting the choice of reperfusion therapy include time between onset of chest pain and presentation, patient characteristics at presentation (high vs. low risk), and access to a skilled facility capable of primary PCI.
Time from symptom onset.
The most important determining factor is the time from symptom onset, which directly correlates with the clinical outcome in patients with STEMI regardless of the reperfusion method. If the symptom duration is < 3 hours, and the door-to-balloon minus door-to-needle time is < 1 hour, primary PCI is preferred. However, if the estimated time from first medical contact to balloon inflation is > 90 minutes (or door-to-balloon minus door-to-needle time is > 1 hour), fibrinolytic therapy is preferred.7
PCI is the favored strategy when there is a delay between symptom onset and presentation (> 3 hours) and when PCI can be performed in a timely manner with a door-to-balloon time goal of 90 minutes.
High-risk patients. Primary PCI has been shown to have better clinical outcomes in high-risk patients, including those elderly who develop shock within 36 hours of MI, patients with severe heart failure and/or pulmonary edema (Killip class III or IV), and symptom onset within 12 hours. If the clinical scenario describes a STEMI with high-risk features, transfer for primary PCI is favored even if the time from first medical contact to balloon inflation modestly exceeds 90 minutes.
Access to skilled facility capable of primary PCI.
The biggest obstacle to the use of primary PCI for all STEMI patients is the lack of a skilled facility capable of primary PCI. For those patients presenting to facilities without this capability, rapid transfer to a PCI center can produce better outcomes than fibrinolysis, as long as the door-to-balloon time, including inter hospital transport time, is <90 minutes. If, however, rapid transfer is not possible, fibrinolytic therapy should be administered. If patient presents very early after symptom onset (<1 hour), and there are no contraindications to fibrinolytic therapy, the therapy should be administered as it may abort the infarction.13
In patients with high-risk features, rapid transfer to a PCI center is preferred as long as the door-to-balloon time is <90 minutes. Patients who do receive fibrinolytic therapy, especially those with high-risk features (e.g., elderly, anterior MI location), should be electively transferred to a PCI center in the event that rescue PCI is needed.14 Table 2.1
summarizes the criteria for selecting a reperfusion therapy.
The current STEMI guidelines6
indicate that the benefit of PCI over fibrinolytic reperfusion pertains to primary PCI performed in a skilled facility. A skilled facility is defined as a laboratory that performs approximately 400 PCI procedures annually, and at least 36 of them are primary PCI. The PCI should be performed by experienced interventionalists, defined as operators who perform >75 PCI procedures annually, and at least 11 of them are primary PCI.
The suggested relationship between PCI-capable centers and improved outcomes is illustrated by findings from a retrospective analysis of 1997 Medicare claims data demonstrating that the need for coronary artery bypass graft (CABG) surgery after PCI occurred more frequently (2.25% vs. 1.55%; P
< .001) when the procedure was performed by inexperienced staff (> 60 vs. < 30 cases per year) and that the risk of 30-day mortality was higher (4.29% vs. 3.15%; P
< .001) for patients treated at lowvolume PCI centers (< 80 vs. > 160 Medicare cases per year).15