Overview of Revascularization for Acute Coronary Syndromes

Immediate reperfusion is not as urgent in patients with uncomplicated non–ST-segment elevation myocardial infarction (NSTEMI) and unstable angina (non-ST elevation acute coronary syndromes [NSTE-ACS]), in whom a completely occluded infarct-related artery at presentation is uncommon, or in patients with unstable angina who respond to medical therapy. Such patients typically undergo angiography within the first 24 to 72 hours of hospitalization for intermediate- to high-risk NSTE-ACS, or prior to discharge if angiography is pursued for low-risk NSTE-ACS patients, to identify coronary lesions requiring PCI or CABG. (See Risk stratification and management strategy for NSTE-ACS.)

A noninterventional approach and a trial of medical management are used for patients in whom angiography demonstrates:

• Only a small area of myocardium at risk

• Lesion morphology not amenable to PCI

• Anatomically insignificant disease (< 50% coronary stenosis)

• Significant left main disease in patients who are not candidates for CABG

Further, angiography or PCI should be deferred in favor of medical management for patients with a high risk of procedure-related morbidity or mortality.

By contrast, patients with persistent chest pain despite maximal medical therapy or complications (eg, markedly elevated cardiac troponin, presence of cardiogenic shock, acute mitral regurgitation, ventricular septal defect, unstable arrhythmias) should proceed directly to the cardiac catheterization laboratory to identify coronary lesions requiring PCI or CABG.

CABG may be preferred to PCI in the following situations:

• Patients with high complexity coronary disease that involves the left main coronary artery

• Patients with diabetes and multivessel disease involving the left anterior descending artery

• Patients with complex multivessel or diffuse disease

• Patients with severe left ventricular dysfunction with multivessel or complex left main disease who are operative candidates

• Following unsuccessful PCI

• Following PCI that causes coronary artery dissection

• When PCI is technically unfeasible (eg, with lesions that are long or near bifurcation points)

Fibrinolytics are not indicated for unstable angina or NSTEMI (2). Risk outweighs potential benefit.

Emergency PCI is the preferred treatment of ST-segment elevation myocardial infarction (STEMI) when patients present < 12 to 24 hours from symptom onset and PCI is available in a timely fashion (door to first medical contact to balloon-inflation time < 90 minutes, or < 120 minutes if hospital-to-hospital transfer is involved) by an experienced operator (1, 2). Indications for urgent PCI later in the course of STEMI (> 24 hours from symptom onset) include hemodynamic instability and malignant arrhythmias requiring transvenous pacing or repeated cardioversion. If the lesions necessitate emergent CABG (eg, high complexity coronary disease that involves the left main coronary artery, diabetes and multivessel disease involving the left anterior descending artery), there is significant mortality and a higher morbidity rate (3, 4).

If there is likely to be a significant delay in availability of PCI and symptom onset was < 12 hours prior to presentation, thrombolysis should be performed for STEMI patients without contraindications (see table Contraindications to Fibrinolytic Therapy for STEMI) (2). Reperfusion using fibrinolytics is most effective if medications are given in the first few minutes to hours after onset of myocardial infarction. The earlier a fibrinolytic is begun, the better. The goal is a door-to-needle time of 30 to 60 minutes. Greatest benefit occurs within 3 hours, but the medications may be effective up to 12 hours. Used with aspirin, fibrinolytics reduce hospital mortality rate by 40% over aspirin alone (5). Prehospital use of fibrinolytics by trained paramedics can significantly reduce time to treatment and should be considered in situations in which PCI within 90 minutes is not possible, particularly in patients presenting within 3 hours of symptom onset (6).

Regardless, patients who undergo thrombolysis should undergo transfer to a PCI-capable facility for elective angiography and possible PCI between 2 and 24 hours after fibrinolytic administration (2). If chest pain or ST-segment elevation persists ≥ 60 minutes after initiation of fibrinolytics or if pain and ST-segment elevation recur, rescue PCI should be performed immediately.

Characteristics and selection of fibrinolytic medications are discussed elsewhere.