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Revascularization for Acute Coronary Syndromes

By James Wayne Warnica, MD, FRCPC , Professor Emeritus of Cardiac Sciences and Medicine, The University of Calgary

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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.).

Approach to acute coronary syndromes.

Unstable Angina and Non-ST-Segment Elevation Myocardial Infarction

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

  • 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 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 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.

ST-Segment Elevation Myocardial Infarction

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.

Fibrinolytic Therapy for STEMI



ECG criteria*

ST-segment elevation in 2 contiguous leads

Typical symptoms and left bundle branch block not known to be old

Strictly posterior MI (large R wave in V1 and ST depression in V1–V4

Absolute contraindications

Aortic dissection

Previous hemorrhagic stroke (at any time)

Previous ischemic stroke within 1 yr

Active internal bleeding (not menses)

Intracranial tumor


Relative contraindications

BP > 180/110 mm Hg after initial antihypertensive therapy

Trauma or major surgery within 4 wk

Active peptic ulcer


Bleeding diathesis

Noncompressible vascular puncture

Current anticoagulation (INR > 2)

*Patients presenting in the hyperacute phase of MI with giant T waves do not meet current criteria for fibrinolytics; ECG is repeated in 20 to 30 min to see if ST-segment elevation has developed.

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