Revascularization for Acute Coronary Syndromes
Revascularization is the restoration of blood supply to ischemic myocardium in an effort to limit ongoing damage, reduce ventricular irritability, and improve short-term and long-term outcomes. Modes of revascularization include
The use, timing, and modality of revascularization depend on which acute coronary syndrome (ACS) is present, timing of presentation, extent and location of anatomic lesions, and availability of personnel and facilities (see Figure: Approach to acute coronary syndromes.).
Immediate reperfusion is not as urgent in patients with uncomplicated non–ST-segment elevation myocardial infarction (NSTEMI), 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 48 h of hospitalization to identify coronary lesions requiring PCI or CABG.
A noninterventional approach and a trial of medical management are used for patients in whom angiography demonstrates
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 markers, 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.
As in patients with stable angina, CABG is generally preferred over PCI for patients with left main or left main equivalent disease and for those with left ventricular dysfunction or diabetes. CABG must also be considered when PCI is unsuccessful, cannot be used (eg, in lesions that are long or near bifurcation points), or causes acute coronary artery dissection.
Fibrinolytics are not indicated for unstable angina or NSTEMI. Risk outweighs potential benefit.
Emergency PCI is the preferred treatment of ST-segment elevation myocardial infarction (STEMI) when available in a timely fashion (door to balloon-inflation time < 90 min) by an experienced operator. Indications for urgent PCI later in the course of STEMI include hemodynamic instability, malignant arrhythmias requiring transvenous pacing or repeated cardioversion, and age > 75. If the lesions necessitate CABG, there is about 4 to 12% mortality and a 20 to 43% morbidity rate.
If there is likely to be a significant delay in availability of PCI, thrombolysis should be done for STEMI patients meeting criteria (see Table: Fibrinolytic Therapy for STEMI). Reperfusion using fibrinolytics is most effective if 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 min. Greatest benefit occurs within 3 h, but the drugs may be effective up to 12 h. Used with aspirin, fibrinolytics reduce hospital mortality rate by 30 to 50% and improve ventricular function. Prehospital use of fibrinolytics by trained paramedics can significantly reduce time to treatment and should be considered in situations in which PCI within 90 min is not possible, particularly in patients presenting within 3 h of symptom onset.
Regardless, most patients who undergo thrombolysis will ultimately require transfer to a PCI-capable facility for elective angiography and PCI as necessary before discharge. PCI should be considered after fibrinolytics if chest pain or ST-segment elevation persists ≥ 60 min after initiation of fibrinolytics or if pain and ST-segment elevation recur, but only if PCI can be initiated < 90 min after onset of recurrence. If PCI is unavailable, fibrinolytics can be repeated.
Characteristics and selection of fibrinolytic drugs are discussed elsewhere.