Acute Myocardial Infarction

Published May 24, 2017

How are stenoses in nonculprit coronary arteries managed in patients undergoing percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI)?

Emergency reperfusion of ischemic myocardium that is in the process of becoming infarcted is the most important advance in the treatment of ST-segment elevation myocardial infarction (STEMI) over the past three decades and is the primary therapeutic goal. With broad application of reperfusion therapy for STEMI, 30-day mortality rates have progressively declined from more than 20% to less than 5%. Read the new review article on this topic.

Clinical Pearls

Q. Is oxygen supplementation beneficial in the initial management of patients with an acute coronary syndrome and normal oxygen levels?

A. The initial management of acute coronary syndromes includes bed rest with electrocardiogram monitoring and prompt initiation of antithrombotic therapy. Although the routine use of oxygen supplementation is still widespread, current evidence does not support its benefit in patients with normal oxygen levels. Hence, its use is recommended only for patients with hypoxemia (oxygen saturation <90%), respiratory distress, or other risk factors for hypoxemia.

Q. Use of which artery has been advocated for vascular access in patients undergoing percutaneous coronary intervention (PCI)?

A. In response to adverse outcomes associated with bleeding complications of PCI, radial-artery access has been advocated for coronary angiography and PCI, particularly for patients with STEMI, in whom bleeding at the access site is most common. The most recent and largest trial randomly assigned 8404 patients with either STEMI or non-STEMI to radial or femoral access. Radial access was associated with a reduction in the rate of adverse clinical events at 30 days, driven by decreases in deaths and major bleeding events, and was beneficial for both types of acute myocardial infarction. One challenge to rapid adoption of the radial approach in general practice is overcoming the learning curve for achieving the outcomes observed in clinical trials.

Morning Report Questions

Q: What is the general approach to the treatment of acute coronary syndromes without ST-segment elevation?

A: Once a definite or likely diagnosis of an acute coronary syndrome without ST-segment elevation has been made, the patient is triaged to either an invasive strategy or an ischemia-guided strategy (i.e., an initial medical strategy with angiography reserved for evidence of spontaneous or provoked ischemia). An invasive strategy leads to improved outcomes and is favored for the majority of patients; the urgency of angiography (performed with the goal of revascularization) depends on the presence or absence of high-risk features. If initial medical therapy stabilizes the patient’s hemodynamic condition and relieves ischemic discomfort, angiography can proceed within 12 to 24 hours. An even more delayed approach (with angiography performed within 25 to 72 hours) is an option for patients at low immediate risk. In patients whose condition is unstable, urgent PCI is performed, as it is for patients with STEMI.

Table 1. Six Initial Assessment and Management Decisions Pertaining to Patients Presenting with Chest Pain and a Possible Acute Coronary Syndrome.

Q: How are stenoses in nonculprit coronary arteries managed in patients undergoing PCI for ST-segment elevation myocardial infarction?

A: An ongoing controversy in the use of PCI for STEMI is the approach to stenoses in nonculprit coronary arteries. PCI of nonculprit stenoses has been contraindicated on the basis of observational studies, which are subject to selection bias. More recently, three randomized trials with samples of intermediate size (296 to 627 patients) showed reductions in ischemia-driven revascularization and variable effects on the risks of recurrent myocardial infarction and death with PCI of nonculprit stenosis. A 2015 systematic review of five trials involving a total of 1568 patients confirmed a decreased risk of repeat revascularization (relative risk, 0.36; 95% confidence interval [CI], 0.27 to 0.48) and a lower risk of nonfatal myocardial infarction (relative risk, 0.58; 95% CI, 0.36 to 0.93), with an uncertain effect on the risk of death (relative risk, 0.82; 95% CI, 0.53 to 1.26). On the basis of this evidence, PCI of nonculprit lesions may be considered either at the time of primary PCI in hemodynamically stable patients or as a staged procedure (ACC–AHA class IIb recommendation, level of evidence B).