Acute Coronary Syndrome
Discover the causes, symptoms, and life-saving treatments for Acute Coronary Syndrome, a condition that affects millions worldwide.
USMLE Guide: Acute Coronary Syndrome
Acute Coronary Syndrome (ACS) refers to a spectrum of clinical presentations related to insufficient blood supply to the heart muscle. It includes unstable angina (UA), non-ST-segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI). ACS is a critical condition requiring immediate medical attention and intervention. This USMLE guide aims to provide a comprehensive overview of ACS, including its pathophysiology, clinical presentation, diagnosis, and management.
ACS is primarily caused by the rupture of an atherosclerotic plaque within a coronary artery, leading to partial or complete occlusion. The rupture exposes the underlying thrombogenic material, resulting in platelet aggregation and the formation of a thrombus. The thrombus can partially or completely obstruct the coronary artery, leading to myocardial ischemia and subsequent clinical manifestations.
- Unstable Angina (UA): Characterized by new-onset or worsening angina symptoms, occurring at rest or with minimal exertion. The symptoms are often severe, prolonged, and not relieved by nitroglycerin.
- Non-ST-segment Elevation Myocardial Infarction (NSTEMI): In addition to UA symptoms, NSTEMI is diagnosed based on elevated cardiac biomarkers, such as troponin, indicating myocardial necrosis.
- ST-segment Elevation Myocardial Infarction (STEMI): Presents with persistent ST-segment elevation on electrocardiogram (ECG), along with symptoms consistent with myocardial ischemia. Elevated cardiac biomarkers confirm myocardial necrosis.
- History and Physical Examination: Assess for typical symptoms such as chest pain, dyspnea, diaphoresis, and radiation to the left arm or jaw. physical examination may reveal signs of heart failure or abnormal heart sounds.
- Electrocardiogram (ECG): A crucial tool for diagnosing ACS. ST-segment elevation in specific leads indicates STEMI, while ST-segment depression or T-wave inversions suggest NSTEMI or UA.
- Cardiac Biomarkers: Serial measurements of cardiac biomarkers, particularly troponin, help differentiate UA from NSTEMI and confirm myocardial necrosis.
- Coronary Angiography: Invasive procedure to visualize coronary arteries and identify any significant stenosis or occlusion. It provides valuable information for selecting appropriate management strategies.
- Antiplatelet Therapy: Aspirin should be administered immediately, followed by P2Y12 inhibitors (e.g., clopidogrel, ticagrelor) to prevent further platelet aggregation.
- Anticoagulation: Low-molecular-weight heparin (LMWH) or unfractionated heparin should be initiated to prevent thrombus formation and extension.
- Pain Relief: Sublingual nitroglycerin is the initial treatment for angina symptoms. Opioids can be used for severe pain not relieved by nitroglycerin.
- Revascularization: Percutaneous coronary intervention (PCI) is the preferred revascularization strategy, involving the use of stents to restore blood flow. Thrombolytic therapy can be considered if PCI is not readily available.
- Secondary Prevention: Statins, beta-blockers, angiotensin-converting enzyme inhibitors (ACE inhibitors), and lifestyle modifications (smoking cessation, exercise, healthy diet) are crucial for long-term management and reducing the risk of future cardiovascular events.
Remember, ACS is a medical emergency requiring prompt diagnosis and treatment to minimize myocardial damage and improve patient outcomes.
Note: This USMLE guide provides a concise overview of ACS, but it is essential to refer to comprehensive textbooks and guidelines for more in-depth study.
- Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 11th Edition.
- American College of Cardiology/American Heart Association Guidelines for the Management of Patients With Acute Coronary Syndromes.