A 71-year-old man develops worsening chest pressure while shoveling snow in the morning. He tells his wife that he has a squeezing pain that is radiating to his jaw and left arm. His wife calls for an ambulance. On the way, he received chewable aspirin and 3 doses of sublingual nitroglycerin with little relief of pain. He has borderline diabetes and essential hypertension. He has smoked 15–20 cigarettes daily for the past 37 years. His blood pressure is 172/91 mm Hg, the heart rate is 111/min and the temperature is 36.7°C (98.0°F). On physical examination in the emergency department, he looks pale, very anxious and diaphoretic. His ECG is shown in the image. Troponin levels are elevated. Which of the following is the best next step in the management of this patient condition?

Clopidogrel, atenolol, anticoagulation and monitoring

CT scan of the chest with contrast

A 54-year-old man is brought to the emergency department 1 hour after the sudden onset of shortness of breath, severe chest pain, and sweating. He has hypertension and type 2 diabetes mellitus. He has smoked one pack and a half of cigarettes daily for 20 years. An ECG shows ST-segment elevations in leads II, III, and avF. The next hospital with a cardiac catheterization unit is more than 2 hours away. Reperfusion pharmacotherapy is initiated. Which of the following is the primary mechanism of action of this medication?

Conversion of plasminogen to plasmin

Inhibition of glutamic acid residue carboxylation

Blocking of adenosine diphosphate receptors

Direct inhibition of thrombin activity

Prevention of thromboxane formation

A 74-year-old man presents to the emergency department by paramedics for slurred speech and weakness in the left arm and leg for 1 hour. The patient was playing with his grandson when the symptoms started and his wife immediately called an ambulance. There is no history of head trauma or recent surgery. The patient takes captopril for hypertension. The vital signs include: pulse 110/min, respiratory rate 22/min, and blood pressure 200/105 mm Hg. The physical examination shows that the patient is alert and conscious, but speech is impaired. Muscle strength is 0/5 in the left arm and leg and 5/5 in the right arm and leg. A non-contrast CT of the head shows no evidence of intracranial bleeding. The lab results are as follows: Serum glucose 90 mg/dL Sodium 140 mEq/L Potassium 4.1 mEq/L Chloride 100 mEq/L Serum creatinine 1.3 mg/dL Blood urea nitrogen 20 mg/dL Cholesterol, total 240 mg/dL HDL-cholesterol 38 mg/dL LDL-cholesterol 100 mg/dL Triglycerides 190 mg/dL Hemoglobin (Hb%) 15.3 g/dL Mean corpuscular volume (MCV) 83 fL Reticulocyte count 0.8% Erythrocyte count 5.3 million/mm3 Platelet count 130,000/mm3 Partial thromboplastin time (aPTT) 30 sec Prothrombin time (PT) 12 sec Although he is within the time frame for the standard therapy of the most likely condition, the treatment cannot be started because of which of the following contraindications?

Systolic blood pressure of 200 mm Hg

A platelet count of 130,000/mm3

A 58-year-old woman is brought to the emergency department for shortness of breath and chest pain. Pulmonary angiography shows a large saddle embolus in the pulmonary arteries. Emergency drug therapy is administered and she is admitted to the hospital for observation. A follow-up CT scan of the chest shortly after admission shows that the thrombus has disappeared. Five hours later, the patient is found to be lethargic with slurred speech. Physical examination shows decreased consciousness, dysarthria, and optic disc swelling bilaterally. Which of the following is the most likely cause of her neurological symptoms?

Embolic cerebrovascular accident

Idiopathic intracranial hypertension

A 55-year-old man comes to the emergency department because of left-sided chest pain and difficulty breathing for the past 30 minutes. His pulse is 88/min. He is pale and anxious. Serum studies show increased cardiac enzymes. An ECG shows ST-elevations in leads I, aVL, and V5-V6. A percutaneous coronary intervention is performed. In order to localize the site of the lesion, the catheter must pass through which of the following structures?

Left coronary artery → left circumflex artery

Right coronary artery → posterior descending artery

Left coronary artery → left anterior descending artery

Right coronary artery → right marginal artery

Left coronary artery → posterior descending artery

A 70-year-old man is brought to the emergency room with complaints of severe substernal chest pain for the last hour. The pain started suddenly, and the patient describes the pain as “going into the shoulder”. The patient took aspirin at home and has been given multiple doses of sublingual nitroglycerin, but the pain has not subsided. He has a blood pressure of 112/84 mm Hg, the pulse is 63/min, the respiratory rate is 18/min, and the temperature is 36.9°C (98.0°F). Cardiac auscultation reveals normal S1 and S2 sounds, however, an additional S4 sound is heard. The patient is sweating profusely, and the lungs are clear to auscultation. No jugular venous distension or pedal edema is observed. His initial ECG shows ST elevation in leads II, III, and aVF. Which of the following will likely have the most benefit in this patient?

Percutaneous coronary intervention

A 53-year-old man with a past medical history significant for hyperlipidemia, hypertension, and hyperhomocysteinemia presents to the emergency department complaining of 10/10 crushing, left-sided chest pain radiating down his left arm and up his neck into the left side of his jaw. His ECG shows ST-segment elevation in leads V2-V4. He is taken to the cardiac catheterization laboratory for successful balloon angioplasty and stenting of a complete blockage in his left anterior descending coronary artery. Echocardiogram the following day shows decreased left ventricular function and regional wall motion abnormalities. A follow-up echocardiogram 14 days later shows a normal ejection fraction and no regional wall motion abnormalities. This post-infarct course illustrates which of the following concepts?

Coronary collateral circulation

Reperfusion strategies for USMLE Step 3: High-Yield Internal Medicine Lessons

Reperfusion 101 - Race Against Time

Goal: Rapidly restore coronary blood flow; "Time is muscle."
Primary PCI (Percutaneous Coronary Intervention): Preferred method.
- Angioplasty ± stent.
- Door-to-balloon time goal: < 90 minutes.
Thrombolysis (Fibrinolysis): Use if PCI is delayed (> 120 min).
- Agents: Alteplase (tPA), Tenecteplase.
- Door-to-needle time goal: < 30 minutes.
- ⚠️ Major risk: Bleeding. Screen for contraindications.

Angioplasty with stent placement in coronary artery

⭐ If transfer time to a PCI-capable hospital is > 120 minutes, initiate thrombolysis at the presenting non-PCI facility before transfer.

Primary PCI - The Gold Standard

Definition: Mechanical revascularization via catheterization, involving balloon angioplasty and/or stent placement to open a blocked coronary artery. Preferred strategy for STEMI if available in a timely manner.
Key Goal: Achieve TIMI grade 3 flow (normal perfusion) in the infarct-related artery.

Timelines are Critical:

Door-to-Balloon (D2B) Time: < 90 minutes at a PCI-capable hospital.
Transfer Patients: First Medical Contact (FMC) to device time should be < 120 minutes. If this timeline isn't possible, consider fibrinolytics.

Procedure:

Diagnostic coronary angiography to locate the occlusion.
Balloon angioplasty to compress the plaque.
Stent placement (usually a Drug-Eluting Stent, DES) to scaffold the vessel open.

Angioplasty procedure with balloon catheter

⭐ Radial artery access is now the standard of care for PCI, as it significantly ↓ bleeding complications and mortality compared to femoral access.

Fibrinolysis - The Clot Dissolver

Indication: STEMI when primary PCI is unavailable within 120 minutes of first medical contact. Most effective if given within 12 hours of symptom onset.
- Goal: Door-to-needle time < 30 minutes.
Mechanism: Converts plasminogen to plasmin, which degrades fibrin, dissolving the thrombus.
Agents: Alteplase (tPA), Reteplase (rPA), and Tenecteplase (TNK-tPA).
- TNK-tPA is fibrin-specific and given as a single IV bolus.
⚠️ Key Absolute Contraindications:
- Any prior intracranial hemorrhage (ICH).
- Known structural cerebral vascular lesion (e.g., AVM).
- Ischemic stroke within 3 months.
- Suspected aortic dissection.
- Active bleeding or significant closed-head/facial trauma within 3 months.

⭐ The most feared complication is intracranial hemorrhage. Risk is highest in the elderly, females, and patients with low body weight or uncontrolled hypertension.

High-Yield Points - ⚡ Biggest Takeaways

PCI is the gold standard for STEMI reperfusion, with a target door-to-balloon time of < 90 minutes.

Use fibrinolysis if PCI is not available within 120 minutes of first medical contact.

Fibrinolytics are most effective within 3 hours of symptom onset.

Key contraindications to fibrinolysis include prior intracranial hemorrhage, active bleeding, or recent major trauma/surgery.

All patients receive dual antiplatelet therapy (DAPT), typically aspirin and a P2Y12 inhibitor, post-reperfusion.

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