Coronary artery disease (CAD) is a leading cause of morbidity and mortality worldwide. Among its clinical manifestations, acute coronary syndromes (ACS) and stable angina are critical conditions that require immediate attention and appropriate management. This article provides an overview of the diagnosis and treatment of ST-Elevation Myocardial Infarction (STEMI), Non-ST-Elevation Myocardial Infarction (NSTEMI), Unstable Angina, and Stable Angina.
Stable Angina
Definition and Pathophysiology:
Stable angina is characterized by predictable chest pain that occurs with exertion or stress and is relieved by rest or nitroglycerin. It results from a fixed atherosclerotic plaque that limits coronary blood flow during increased myocardial demand.
Diagnosis:
History and Physical Examination: Characteristic chest pain that is predictable and consistent in nature.
Electrocardiogram (ECG): Typically normal at rest; stress testing may reveal ischemic changes.
Imaging and Tests: Stress testing (exercise ECG, stress echocardiography, or nuclear imaging) and coronary angiography for definitive diagnosis.
Treatment:
Lifestyle Modifications: Smoking cessation, diet changes, and regular exercise.
Medications: Antianginals (e.g., nitrates, beta-blockers, calcium channel blockers), antiplatelets (aspirin), statins, and ACE inhibitors.
Revascularization: Percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) in refractory cases.
Unstable Angina
Definition and Pathophysiology:
Unstable angina is characterized by new-onset angina, angina at rest, or a change in the pattern of previously stable angina. It is often caused by a rupture of an atherosclerotic plaque with partial thrombus formation.
Diagnosis:
History and Physical Examination: Angina that is more severe, prolonged, or occurs at rest.
ECG: May show ST-segment depression, T-wave inversion, or transient ST-segment elevation.
Biomarkers: Cardiac troponins are not elevated, distinguishing it from NSTEMI.
Treatment:
Immediate Management: Hospital admission, bed rest, oxygen, and analgesia (e.g., morphine).
Medications: Antiplatelets (aspirin, clopidogrel), anticoagulants (heparin), nitrates, beta-blockers, and statins.
Revascularization: Considered if symptoms persist or if there is evidence of significant ischemia on non-invasive testing.
NSTEMI (Non-ST-Elevation Myocardial Infarction)
Definition and Pathophysiology:
NSTEMI occurs due to partial or intermittent occlusion of a coronary artery by a thrombus, leading to myocardial necrosis.
Diagnosis:
History and Physical Examination: Similar to unstable angina but more severe.
ECG: ST-segment depression or T-wave inversion; no ST-segment elevation.
Biomarkers: Elevated cardiac troponins indicating myocardial injury.
Treatment:
Immediate Management: Similar to unstable angina.
Medications: Dual antiplatelet therapy (aspirin and P2Y12 inhibitors), anticoagulants, beta-blockers, nitrates, statins, and ACE inhibitors.
Revascularization: Early invasive strategy with PCI or CABG based on risk stratification.
STEMI (ST-Elevation Myocardial Infarction)
Definition and Pathophysiology:
STEMI is caused by complete occlusion of a coronary artery, leading to full-thickness myocardial infarction.
Diagnosis:
History and Physical Examination: Severe, crushing chest pain often radiating to the left arm or jaw.
ECG: ST-segment elevation in two or more contiguous leads or new left bundle branch block (LBBB).
Biomarkers: Significantly elevated cardiac troponins.
Treatment:
Immediate Management: Activation of emergency response, oxygen, analgesia (morphine), nitrates, and antiplatelet therapy.
Reperfusion Therapy: Primary PCI within 90 minutes of first medical contact is preferred. Thrombolytic therapy if PCI is not available within the timeframe.
Medications Post-Reperfusion: Dual antiplatelet therapy, beta-blockers, ACE inhibitors, statins, and anticoagulants.
Diagnostic Tools
Electrocardiogram (ECG): Key for differentiating between STEMI, NSTEMI, and unstable angina.
Cardiac Biomarkers: Troponins are crucial for diagnosing myocardial infarction (both STEMI and NSTEMI).
Imaging: Echocardiography, stress testing, and coronary angiography for definitive assessment and management planning.
Conclusion
Prompt recognition and differentiation between STEMI, NSTEMI, unstable angina, and stable angina are essential for effective treatment and improved patient outcomes. Emergency physicians must be adept at utilizing diagnostic tools and implementing appropriate therapeutic strategies to manage these conditions effectively.
References
Amsterdam, E. A., Wenger, N. K., Brindis, R. G., et al. (2014). "2014 AHA/ACC guideline for the management of patients with non–ST-elevation acute coronary syndromes: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines." Circulation, 130(25), e344-e426.
O'Gara, P. T., Kushner, F. G., Ascheim, D. D., et al. (2013). "2013 ACCF/AHA guideline for the management of ST-elevation myocardial infarction: executive summary." Circulation, 127(4), 529-555.
Fihn, S. D., Gardin, J. M., Abrams, J., et al. (2012). "2012 ACCF/AHA/ACP/AATS/PCNA/SCAI/STS guideline for the diagnosis and management of patients with stable ischemic heart disease." Circulation, 126(25), e354-e471.
Anderson, J. L., Adams, C. D., Antman, E. M., et al. (2007). "ACC/AHA 2007 guidelines for the management of patients with unstable angina/non–ST-elevation myocardial infarction." Circulation, 116(7), e148-e304.
