A 29-Year-Old Black Male Presents to the Emergency Department with Chest Pain

A 29-year-old black male presents to the emergency department with chest pain. The symptoms were described as an acute onset of moderate substernal tightness radiating to the upper back. There was associated dyspnea, but no nausea, vomiting, or diarrhea. His symptoms were considered atypical in that they were exacerbated by stretching, deep breathing, and movement. The symptoms were different from his prior sickle cell pain crises. As there was no relief with self-administered Percocet at home, he came to the emergency department.

Figure 1
A 29-Year-Old Black Male Presents to the Emergency Department with Chest Pain
Past medical history: No cardiac history; sickle cell anemia with frequent sickle cell crises, most recently 1 month prior to admission

Social: Smokes one pack per day; no illicit drug use

Family history: Negative for premature coronary disease

Physical exam: Blood pressure 126/60 mm Hg, pulse 87 bpm, respirations 16, afebrile; oxygen saturation 99% on 2 L supplemental oxygen

Head, ears, eyes, nose, throat (HEENT): Mild scleral icterus

Lungs: Clear

Heart: Regular rate and rhythm, 1/6 systolic ejection murmur at left upper sternal border; no rub or gallop

Extremities: No edema

ECG: Normal sinus rhythm, without ischemic changes

Laboratory values: Hemoglobin 8.0, white blood cell count 20.2K, platelets normal, blood urea nitrogen/creatinine 6/0.8

Cardiac markers:
   2:30   5:30   11:30   21:30 
Troponin I, ng/ml 4.6 5.3 2.5 0.7
Myocardial band (MB), ng/ml   6.6 6.0 4.2 1.1
Creatine kinase (CK), U/L 166 155 161 139
Emergency department course: The patient was initially considered low risk based on age and absence of ECG changes, and underwent acute rest myocardial perfusion imaging (MPI) for further risk stratification. This demonstrated a small sized, low-moderate grade inferior apical defect (Figure 1). Gated images demonstrated abnormal wall motion, and the study was interpreted as consistent with an acute coronary syndrome. The patient was admitted to the coronary intensive care unit. Serial markers were performed:

An echocardiogram demonstrated a mid and distal inferior wall motion abnormality with mild hypokinesia with preserved systolic function. No significant valvular abnormalities were observed, and right ventricular (RV) function was normal.

Based on the initial presentation and elevated cardiac markers, the patient was treated for acute coronary syndrome. Enoxaparin, aspirin, intravenous nitroglycerin, and metoprolol were initiated, with subsequent symptom resolution. The next day, a coronary angiography was performed, which showed normal coronary arteries. A left ventriculogram showed distal inferior hypokinesis.

Which of the following is the most likely cause for the patient's troponin elevations?

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