USMLE Step 3 - Question 9

A 72 year old female with a history of diabetes mellitus presents to the emergency department with chest pains at rest intermittently for the past 4 hours. She has associated shortness of breath and diaphoresis. Her heart rate is 59, blood pressure 134/72, respiratory rate 20, and oxygen saturation 95% on room air. Physical examination reveals normal lung sounds and an S4 gallop. Her ECG reveals 1 mm ST segment depressions in leads V1 to V4. She is given aspirin immediately. Her troponin levels remain negative. She is currently chest pain free. Which of the following is the next appropriate step in her management?

A. Emergent cardiac catheterization

B. Intravenous glycoprotein IIb/IIIa inhibitor

C. Intravenous nitroglycerine drip

D. Intravenous heparin drip

The patient in question #9 is clearly suffering from chest pain due to myocardial ischemia. Since the pain occurred at rest and she has no prior history of heart disease, then she has unstable angina. Remember that there are three categories of acute coronary syndromes: unstable angina (UA), non-ST segment elevation MI (NSTEMI), and ST segment elevation MI (STEMI). Also recall that there are 3 different patient presentations that can be classified into unstable angina:

1. New onset cardiac chest pain (even if it gets worse with exertion and better with rest, the first time it occurs it is considered UA)

2. Cardiac chest pain at rest without ST elevation on the ECG and with negative cardiac biomarkers (troponin)

3. Worsening of known stable angina (used to be able to walk 1 block before getting chest pain and can now only walk 1/2 block). ECG findings in unstable angina can vary from a normal ECG to dramatic ST segment depressions.

A non-ST segment elevation myocardial infarction (NSTEMI) occurs when a patient experiences chest pain from myocardial ischemia and the serum biomarkers of myocardial necrosis (troponins) are significantly elevated despite not showing ST segment elevation on the ECG. Findings on ECG in a NSTEMI can vary from a normal ECG to dramatic ST segment depressions like in UA.

A ST segment elevation myocardial infarction (NSTEMI) occurs when a patient experiences chest pain from myocardial ischemia, the serum biomarkers of myocardial necrosis (troponins) are significantly elevated, and ST segment elevation is seen on the ECG.

While cardiac catheterization is reasonable to pursue at some point, there is no indication for emergent cardiac catheterization since there is ST segment elevation. Glycoprotein IIb/IIIa inhibitors are not indicated as a part of medical management of unstable angina, however they can be used in NSTEMI patients. Nitroglycerine is used in acute coronary syndromes for chest pain relief or control of blood pressure and our patient requires neither.