Acute Coronary Syndrome Overview

Acute Coronary Syndrome

• Encompasses symptoms and clinical findings with acute myocardial ischemia
• Usually precipitated by acute thrombosis from a ruptured or eroded atherosclerotic coronary plaque (unstable plaque) and coronary thrombosis
• Spectrum includes ST Elevation MI (STEMI), Non ST Elevation MI (NSTEMI), and Unstable Angina (UA)

ST Elevation MI (STEMI)

• Complete blockage of a coronary artery
• Specific ECG changes: significant ST-segment elevation in two contiguous leads
• Often presents with severe prolonged chest pain (may radiate to arms/jaw/back), shortness of breath (SOB), sweating (diaphoresis), nausea/vomiting (N/V)

Non ST Elevation MI (NSTEMI)

• Partial blockage of a coronary artery
• Nonspecific ECG changes: ST-segment depression, T-wave inversion, or no changes
• Symptoms similar to STEMI, may be less severe

Unstable Angina (UA)

• New onset angina, increasing angina, or angina at rest
• Reflects a significant disruption in coronary artery blood flow without evidence of myocardial necrosis

Myocardial Infarction

• Defined as a rise and/or fall of cardiac biomarkers PLUS one of:
  • Symptoms of ischemia
  • Development of pathologic Q waves on the ECG
  • New or presumed new ST changes on ECG or new Left Bundle Branch Block (LBBB)
  • Identification of intracoronary thrombus by angiography or autopsy
  • Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
• Classification of Myocardial Infarction includes:
  • Type 1 MI: pathologic process in the wall of the coronary artery (plaque rupture, fissuring, dissection)
  • Type 2 MI: results from a critical imbalance between myocardial oxygen supply and demand (coronary spasm, anemia, arrhythmias, hypotension, hypertension, respiratory failure)
  • Type 3 MI: MI resulting in death for which cardiac enzymes are not available
  • Type 4 MI: MI related to PCI/stent thrombosis
  • Type 5 MI: MI related to CABG

Approach to Acute Chest Pain

• Differential diagnosis includes: acute coronary syndrome, aortic dissection, pulmonary embolism, pneumothorax, pericarditis/cardiac tamponade/myocarditis, esophageal spasm, GERD, mediastinitis, respiratory tract infections, asthma exacerbations, musculoskeletal causes, anxiety.

Immediate Management

• Monitor vital signs, including blood pressure in both arms
• Administer supplemental oxygen if SpO2 <90%
• Establish intravenous (IV) access
• Obtain electrocardiogram (ECG) within 10 minutes of medical contact
• Obtain medical history and perform a physical examination
• Order complete blood count (CBC), electrolytes, blood urea nitrogen (BUN), creatinine (Cr), troponin, creatine kinase (CK), and chest x-ray (CXR)

STEMI Management

• Primary goal is to open the infarct-related artery as quickly as possible to restore perfusion using either primary percutaneous coronary intervention (PCI) or fibrinolytic therapy
• Factors determining treatment strategy include patient presentation, risk factors, and time from onset of symptoms to receiving treatment

NSTEMI Management

• Treatment strategy depends on the TIMI (Thrombolysis in Myocardial Infarction) risk score, which assesses risk factors for adverse outcomes
• Consider a less aggressive strategy than STEMI, including medical therapy, if the risk score is low. Conversely, more aggressive treatment such as early invasive management (coronary angiography and revascularization) is considered if the score is high.

Causes of Elevated Troponin

• Cardiac muscle damage releases troponin into the bloodstream
• Potential causes of elevated troponin include critical illnesses (e.g., diabetes, respiratory failure, sepsis), pericarditis/myocarditis, and situations where the heart has to work harder (e.g., exertion, hypertensive crisis).

Surgical Revascularization (CABG)

• Used to improve blood flow to the heart muscle in individuals with significant coronary artery disease (CAD) by creating new pathways for blood flow.
• Suitable for cases involving complex CAD, particularly if there are multiple vessel involvements or impaired left main coronary artery or left ventricular dysfunction.