USMLE Step 3 - Question 22

A 45 year old male with a history of hypertension and dyslipidemia presents to the emergency department with substernal chest pressure for 1 hour. The pain occurred at rest, is 10/10 in severity and is associated with shortness of breath. His temperature is 37.1 C, blood pressure 80/50, heart rate 90, and respirations 20. His laboratory studies are normal. His ECG is below. What is the appropriate initial management?

A. Intravenous beta-blockers

B. Sublingual nitroglycerine

C Intravenous heparin

D. Intravenous dobutamine

The ECG reveals an anterior wall ST segment elevation myocardial infarction. The mnemonic for treatment of an acute coronary syndrome is "MONA B".

M - morphine (only given if nitroglycerine does not relieve the chest pain or if pulmonary edema present)
O - oxygen
N - nitroglycerine (should not be given if systolic blood pressure less than 90 mmHg)
A - aspirin
B - beta-blockers (should not be given if systolic blood pressure less than 90, heart rate < 60, or cardiogenic shock is suspected)

Unfortunately there is no H in MONA B to remember heparin which is indicated in all acute coronary syndromes. Dobutamine, an positive intropic agent, would not be given immediately since it would worsen myocardial ischemia by increasing myocardial oxygen demand (thus increasing the size of the infarct). The emergent treatment should be cardiac catheterization, intra-aortic balloon counterpulsation (IABP) and if necessary afterwards if shock is still present, then dobutamine (or milrinone) can be given.