On postoperative day 5 after surgery, a patient develops fever and tachycardia. What is the most likely cause?

• A. Postoperative infection (pneumonia, UTI, or wound infection)
• B. Pulmonary embolism
• C. Myocardial infarction
• D. Drug fever

Answer: (C)

Surgery is a major stress on the body, and the heart can become vulnerable to ischemia in the days after a procedure. A myocardial infarction can present with fever and tachycardia due to the inflammatory response to myocardial necrosis and the body’s stress response, even if chest pain isn’t prominent. The postoperative period also elevates oxygen demand and can destabilize any underlying plaque, precipitating an ACS.

While infections (pneumonia, UTI, wound infection), pulmonary embolism, and drug fever can cause fever and tachycardia, they typically have additional clues: infections usually show localized symptoms or leukocytosis, PE often brings acute dyspnea and chest pain with hypoxemia, and drug fever tends to align with a new medication history. The combination of fever with tachycardia after several days of surgery most strongly raises concern for an acute coronary syndrome in this context.

The key takeaway is to evaluate promptly for myocardial ischemia with ECG and troponin, because postoperative MI is a critical, time-sensitive diagnosis.