USMLE Q Bank Step 1 – 203

A 55 year-old man underwent internal fixation of fractured femur after a motorcar accident and massive bleeding 24 hours ago. He was stable after the surgery and his urine output was normal after he received intravenous fluids. Now he complains of substernal chest pain and shortness of breath. On examination, His temperature is 98.8 F, Pulse is 110/min, blood pressure is 160/100 mmHg and his respiratory rate is 24/min. There is no jugular vein distention. His extremities have established pulses bilaterally and good perfusion. Auscultation reveals harsh systolic murmur across the precordium and crackles on both lung bases. ECG shows sinus tachycardia with delayed precordial transition and no other changes. Laboratory tests including cardiac enzymes are all normal.

What is the most likely diagnosis?

A- Acute myocardial infarction

B- Left bundle branch block (LBBB)

C- Septic shock

D- Hypertrophic cardiomyopathy

E- Pericardial effusion


This patient has a typical presentation of hypertrophic cardiomyopathy with outflow obstruction, which is exacerbated due to excessive loss of blood. It is suggested by systolic murmur, vital signs and ECG findings. Negative ECG for coronary obstruction and laboratory findings exclude MI and LBBB. There is no signs suggest septic shock. Normal jugular venous pressure, clinical findings and ECG changes make pericardial effusion less likely the correct diagnosis.

The  correct answer is D

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