Cardiology · Acute Coronary Syndrome
The facts most likely to be tested
An NSTEMI is defined by the presence of elevated cardiac troponins in the setting of ischemic symptoms without ST-segment elevation on the 12-lead ECG.
The initial management of NSTEMI includes dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 inhibitor (e.g., ticagrelor or clopidogrel).
Anticoagulation with unfractionated heparin, enoxaparin, or fondaparinux is mandatory to prevent further thrombus propagation.
Beta-blockers are indicated within 24 hours to reduce myocardial oxygen demand and the risk of ventricular arrhythmias.
High-intensity statin therapy (e.g., atorvastatin) must be initiated immediately to provide plaque stabilization and long-term cardiovascular risk reduction.
Early invasive strategy (coronary angiography within 24 hours) is indicated for patients with high-risk features such as hemodynamic instability, refractory angina, or dynamic ST-segment changes.
Nitroglycerin is used for symptomatic relief of ischemic chest pain but does not provide a mortality benefit in the acute setting.
Vignette unlocked
A 68-year-old male with a history of hypertension and hyperlipidemia presents to the emergency department with 2 hours of substernal chest pressure radiating to his left jaw. His ECG shows ST-segment depression in leads V4-V6 but no ST-segment elevation. His initial troponin I is significantly elevated at 1.5 ng/mL. He is currently hemodynamically stable with a blood pressure of 135/85 mmHg.
What is the most appropriate next step in the pharmacological management of this patient?
Initiation of dual antiplatelet therapy (aspirin and a P2Y12 inhibitor) and anticoagulation.
This patient presents with an NSTEMI, and the standard of care requires immediate initiation of DAPT and anticoagulation to prevent further thrombus formation as outlined in the second and third bets.
Full handout
High yield triage
Etiology / Epidemiology
Caused by coronary artery plaque rupture with subtotal occlusion. Primary risk factors: HTN, DM, smoking, dyslipidemia.
Clinical Manifestations
Substernal levine sign chest pain without ST-elevation. Elevated cardiac troponins are the diagnostic hallmark.
Diagnosis
Serial troponins and ECG showing ST-depression or T-wave inversion. Coronary angiography is the gold standard.
Treatment
Dual antiplatelet therapy (DAPT) and heparin. Avoid nitrates in right ventricular infarction.
Prognosis
Risk stratified by TIMI score. Monitor for arrhythmias and heart failure post-MI.
Full handout
Epidemiology & Etiology
NSTEMI occurs when a coronary plaque ruptures, causing partial vessel occlusion or distal embolization. Diabetes mellitus is a major risk factor, often presenting with silent ischemia. Incidence increases with age, male sex, and family history of premature CAD.
Pertinent Anatomy
Involves the epicardial coronary arteries (LAD, LCx, or RCA). Ischemia typically affects the subendocardium, which is the most vulnerable layer to hypoperfusion due to high wall tension.
Pathophysiology
Plaque rupture leads to platelet aggregation and thrombus formation. Unlike STEMI, the vessel remains patent enough to prevent transmural necrosis. This results in myocardial ischemia without full-thickness injury, manifesting as elevated biomarkers without ST-segment elevation.
Clinical Manifestations
Patients present with retrosternal chest pressure radiating to the jaw or left arm, often described as the Levine sign. Red flags include diaphoresis, syncope, or new-onset S3 gallop. Symptoms are often relieved by rest but are more persistent than stable angina.
Diagnosis
Diagnosis requires elevated cardiac troponin I or T above the 99th percentile of the upper reference limit. ECG may show ST-segment depression or T-wave inversion. Coronary angiography is the definitive gold standard for identifying the culprit lesion.
Treatment
Initial management includes aspirin (325mg) and a P2Y12 inhibitor (e.g., clopidogrel). Administer unfractionated heparin or enoxaparin for anticoagulation. Contraindications for beta-blockers include signs of heart failure or bradycardia. Use nitroglycerin for pain, but avoid in patients taking PDE-5 inhibitors.
Prognosis
Long-term outcomes depend on left ventricular ejection fraction (LVEF). Major complications include ventricular arrhythmias and mechanical complications like papillary muscle rupture. Patients require aggressive statin therapy and lifestyle modification.
Differential Diagnosis
Aortic dissection: tearing chest pain radiating to the back
Pulmonary embolism: pleuritic pain with tachycardia/hypoxia
Pericarditis: positional pain relieved by leaning forward
GERD: burning pain relieved by antacids
Stable angina: pain predictable with exertion, relieved by rest