Patients with acute ST-elevation myocardial infarction require reperfusion therapy as early after symptom onset as possible, using either primary PCI or fibrinolytic therapy. Outcomes for both treatment options are closely related to achievement of early, complete, and sustained reperfusion.

The advantages of PCI include higher vessel patency rates, lower reinfarction and stroke rates, and immediate risk stratification. PCI should be performed in patients presenting within the first 12 hours after myocardial infarction if a skilled PCI laboratory is available (operator experience >75 PCI procedures/year in a laboratory with >200 PCI procedures/year, at least 36 of which are for acute myocardial infarction) and the procedure can be performed within 90 minutes (38). If expert, prompt PCI is not available, fibrinolytic therapy should be administered.

There are four subgroups in which PCI is especially preferred because of concerns about the safety or efficacy of fibrinolytic therapy:

1. Patients in whom fibrinolytic therapy is contraindicated
2. Late-arriving ST-elevation myocardial infarction patients presenting more than 12 hours after the onset of chest pain with continued chest pain or ST-elevation
3. Patients with a history of CABG surgery
4. Patients with cardiogenic shock (pulmonary edema and systolic blood pressure <100 mm Hg), especially if younger than 75 years

When primary PCI is performed, therapy with unfractionated heparin also should be initiated, with the dose adjusted depending on the concurrent use of a glycoprotein IIb/IIIa inhibitor. Clopidogrel should be started early and continued for at least 1 month after the insertion of a bare-metal stent. With drug-eluting stents, treatment with clopidogrel for 12 months is often utilized if bleeding risk is low, with a minimal duration of therapy of 3 months (sirolimus-eluting stent) or 6 months (paclitaxel-eluting stent). It is reasonable to start a GP IIb/IIIa inhibitor as early as possible before primary PCI and continue for 12 to 18 hours.

The advantages of fibrinolytic therapy include its availability and ease of use. In the absence of contraindications or when PCI is not available, fibrinolytic therapy should be administered in ST-elevation myocardial infarction patients with symptom onset within the previous 12 hours and ST-segment elevation greater than 0.1 mV in at least 2 contiguous precordial leads or at least 2 adjacent limb leads, or with new or presumed new left bundle branch block (LBBB) or true posterior myocardial infarction. Fibrinolytic therapy should not be administered to asymptomatic patients whose initial symptoms of ST-elevation myocardial infarction began more than 24 hours earlier or whose 12-lead electrocardiogram shows only ST-segment depression, unless a true posterior myocardial infarction is suspected.

Administration of the fibrinolytic agent should be started within 30 minutes of entry to the emergency department. The preferred agent for fibrinolytic therapy in acute ST-elevation myocardial infarction is tenecteplase because of its ease of single bolus administration. Contraindications are listed in Table 9. The most important risk of fibrinolytic therapy is bleeding, particularly intracranial hemorrhage; this is more common in patients with a history of chronic severe hypertension, those who present with severe hypertension, and elderly persons.

There are no data on combining fibrinolytic agents, but the combined use of low-molecular-weight heparin instead of unfractionated heparin with fibrinolytic strategies not only improves ease of administration but also is associated with lower rates of recurrent ischemic complications (39).

Evidence of successful thrombolysis involves resolution of both chest pain and ST elevation. The rapidity with which these resolve is directly related to early patency of the infarct-related artery. Reperfusion arrhythmias, typically manifested as a transient accelerated idioventricular arrhythmia, usually do not require additional antiarrhythmic therapy.

In addition to prompt reperfusion, anticoagulation, and administration of antiplatelet therapy, patients with ST-elevation myocardial infarction should receive nitroglycerin, aspirin, a β-blocker, and narcotic analgesics if needed for pain (Table 10). Aspirin should be administered in the emergency department. Patients with ongoing ischemic discomfort should receive sublingual nitroglycerin (0.4 mg every 5 minutes for a total of 3 doses), after which an assessment should be made regarding the need for intravenous nitroglycerin, which should be used for relief of ongoing ischemic discomfort, control of hypertension, or management of pulmonary congestion. Nitrates should not be administered to patients with systolic blood pressure that is below 90 mm Hg or a systolic blood pressure that is 30 mm Hg or more below baseline, severe bradycardia (<50/min), tachycardia (>100/min), or suspected right ventricular infarction. Morphine sulfate or fentanyl are analgesics of choice for pain associated with ST-elevation myocardial infarction.

Oral β-blocker therapy should be administered promptly to those patients without a contraindication, irrespective of concomitant fibrinolytic therapy or performance of primary PCI, especially if a tachyarrhythmia or hypertension is present. A daily dose should be continued and optimized based on heart rate and blood pressure. An ACE inhibitor should be started in patients with anterior infarction, pulmonary congestion, or an ejection fraction less than 40%. Contraindications to ACE inhibitor therapy are hypotension (systolic blood pressure <100 mm Hg or <30 mm Hg below baseline) or known contraindications to this class of medications. Angiotensin receptor blockers are only used in patients who cannot take an ACE inhibitor.

All patients with uncomplicated ST-elevation myocardial infarction should receive supplemental oxygen during the first 6 hours, especially patients with arterial oxygen desaturation (oxygen saturation less than 90% by pulse oximetry).

38. Antman EM, Anbe DT, Armstrong PW, et al. American College of Cardiology; American Heart Association; Canadian Cardiovascular Society. ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction–executive summary. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to revise the 1999 guidelines for the management of patients with acute myocardial infarction). J Am Coll Cardiol. 2004;44:671-719. PMID: 15358045
39. Antman EM, Louwerenburg HW, Baars HF, Wesdorp JC, Hamer B, Bassand JP, et al. Enoxaparin as adjunctive antithrombin therapy for ST-elevation myocardial infarction: results of the ENTIRE-Thrombolysis in Myocardial Infarction (TIMI) 23 Trial. Circulation. 2002;105:1642-9. [PMID: 11940541]

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