Acute Coronary Syndrome Overview

Acute Coronary Syndrome

• Acute coronary syndrome (ACS) encompasses symptoms and clinical findings with acute myocardial ischemia.
• Usually precipitated by acute thrombosis induced by a ruptured and eroded atherosclerotic coronary plaque (unstable plaque).
• Spectrum includes ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI).
• STEMI (complete blockage of artery): Specific ECG changes (significant ST-segment elevation in two contiguous leads), often severe.
• NSTEMI (partial blockage of artery): Nonspecific ECG changes (ST-segment depression, T-wave inversion, or no changes). Symptoms similar to STEMI, may be less severe. Unstable angina (UA) is a type of NSTEMI with symptoms like new onset angina, worsening angina, or angina at rest, but no evidence of myocardial necrosis.
• Myocardial infarction is defined as a rise or fall in cardiac biomarkers plus one of the following: symptoms of ischemia, development of pathologic Q waves on ECG, new or presumed new ST changes, or identification of intracoronary thrombus.

Myocardial Infarction

• Classification includes different types:
  • Type 1 MI: pathologic process in coronary artery wall (plaque rupture, tearing)
  • Type 2 MI: imbalance between oxygen supply and demand (spasm, anemia, arrhythmias).
  • Type 3 MI: MI resulting in death due to lack of cardiac enzyme availability
  • Type 4 MI: MI due to PCI/stent thrombosis
  • Type 5 MI: MI associated with CABG.

Approach to Acute Chest Pain

• Differential diagnoses: acute coronary syndrome, aortic dissection, pulmonary embolism, pneumothorax, pericarditis/cardiac tamponade/myocarditis, esophageal spasm, mediastinitis, respiratory tract infections/pleuritis, asthma exacerbations, musculoskeletal causes (costochondritis, contusions, muscle strains), anxiety.

Immediate Management

• Monitor vital signs (including blood pressure in both arms).
• Oxygen if SpO2 < 90%.
• Establish intravenous access.
• ECG within 10 minutes of contact with medical services
• Obtain history and physical examination
• Conduct CBC, electrolytes, BUN, creatinine, troponin, and CK test.
• Obtain chest x-ray (CXR).

STEMI Management

• Primary goal is to restore coronary blood flow as soon as possible by either:
  • Primary PCI (percutaneous coronary intervention): Mechanical revascularization, preferred if first medical contact to balloon inflation time is under 90-120 minutes.
  • Fibrinolytic therapy (e.g., alteplase, tenecteplase): Pharmacological revascularization, indicated if time to balloon inflation is longer
• Factors affecting choice of treatment include patient characteristics and clinical presentation.
• Consideration of risk factors in medication and procedural treatment.

Medical Therapy

• Antiplatelet agents (e.g., ASA, clopidogrel, prasugrel, ticagrelor): Prevent further clot formation
• Anticoagulation (e.g., heparin, bivalirudin): Reduce clot formation, particularly in PCI patients
• Beta-blockers: Help to manage heart rate and blood pressure.
• Statins: Reduce elevated cholesterol levels
• ACE inhibitors/ARBs: Helpful in patients with reduced left ventricular ejection fraction (<40%).

Causes of Elevated Troponin

• Cardiac muscle damage releases troponin into the bloodstream.
• Elevated troponin levels may signify critical illness, respiratory failure, sepsis.

NSTEMI

• The TIMI (Thrombolysis in Myocardial Infarction) risk score helps assess risk of adverse outcomes.
• Patients can benefit from early invasive management (coronary angiography and revascularization) or intensive medical therapy.

Surgical Revascularization (CABG)

• A procedure used to bypass blocked or narrowed coronary arteries using harvested blood vessels.
• The decision to utilize this approach is individualized based on patient factors.

Take Home Messages

• Acute coronary syndromes involve the mechanism of myocardial ischemia.
• Management of STEMI focuses on opening the occluded artery (medications and intervention).
• Unstable angina and NSTEMI management: initial stabilization followed by risk stratification for early intervention or conservative therapy.
• In Type II MI (supply-demand mismatch), the underlying cause is targeted to improve outcomes.

This quiz covers the key concepts of Acute Coronary Syndrome (ACS), including its causes, symptoms, and classifications such as STEMI and NSTEMI. Understand how these conditions manifest in terms of ECG changes and myocardial infarction. Test your knowledge on this critical topic in cardiovascular medicine.