Key Clinical Questions
What is the optimal care and management of patients with ST-segment elevation myocardial infarction?
What is the optimal care and management of patients with non-ST segment elevation acute coronary syndrome?
The term acute coronary syndrome (ACS) refers to the spectrum clinical presentations related to acute myocardial ischemia or infarction due to the abrupt reduction in coronary blood flow. ACS is divided into ST-segment elevation myocardial infarctions (STEMIs) and non-ST segment elevation acute coronary syndromes (NSTE-ACSs). The NSTE-ACS is further subdivided on the basis of elevated cardiac biomarkers of myocardial necrosis. Patients with elevated cardiac biomarkers are defined as non-ST segment elevation myocardial infarction (NSTEMI) and those without elevated biomarkers are termed unstable angina (UA).
This chapter will focus on the diagnosis, risk stratification, and treatment of patients with ACS based on the American College of Cardiology Foundation and American Heart Association (ACCF/AHA) practice guidelines for STEMI and NSTE-ACS. All guideline recommendations will be cited in this chapter and referenced according the American College of Cardiology Foundation/American Heart Association classification scheme (Table 128-1).
Table 128-1ACCF/AHA Classification of Recommendations and Level of Evidence ||Download (.pdf) Table 128-1 ACCF/AHA Classification of Recommendations and Level of Evidence
|Class I ||Class IIa ||Class IIb ||Class III |
Risk Procedure/ Treatment
SHOULD be performed/ administered
Benefit >> Risk
Additional studies with focused objectives needed
IT IS REASONABLE
to perform procedure/administer treatment
Benefit ≥ Risk
Additional studies with broad objectives needed; Additional registry data would be helpful
MAY BE CONSIDERED
Risk ≥ Benefit
No additional studies needed
Procedure/Treatment should NOT be performed/administered
SINCE IT IS NOT HELPFUL AND MAY BE HARMFUL
|Level A: Recommendation based on evidence from multiple randomized trials or meta-analyses |
|Level B: Recommendation based on evidence from a single randomized trial or non-randomized studies |
|Level C: Recommendation based on expert opinion, case studies, or standard of care |
EPIDEMIOLOGY & PATHOPHYSIOLOGY
ACS is common, with over 780,000 patients experiencing an ACS event every year in the United States. Of these events, approximately 70% are classified as NSTE-ACS. ACS is related to an acute imbalance of myocardial oxygen consumption and demand, usually related to a sudden coronary artery obstruction. Autopsy studies suggest that most ACS events are related to acute coronary thrombosis, with acute plaque rupture being the most common etiology. The atherosclerosis at sites of plaque rupture is characterized by large lipid-laden necrotic cores overlying a disrupted thin fibrous cap. The second most common cause of acute coronary thrombosis is plaque erosion, characterized by thrombus formation at an area of denuded endothelium. These plaques are characterized by ...