A 45-Year-Old Woman With Hypertension and Intermittent Chest Pain

A 45-year-old female with a history of hypertension, elevated cholesterol, and seropositive rheumatoid arthritis presented with intermittent chest pain. She described the symptoms as a sharp stabbing chest pain, lasting seconds to 1-2 minutes, occurring at both rest and with exertion, that were spontaneously relieved. She reported some intermittent associated mild shortness of breath but no diaphoresis, nausea, vomiting, or radiation. The symptoms began approximately one week prior to presentation, and had increased in frequency to approximately 3-4 times a day. She did not report any obvious relieving or exacerbating factors.

She called her primary care physician who referred her to the Emergency Department. She reported that her last episode of chest pain was approximately two hours prior to coming to the ED. In the ED, the initial ECG was normal. 

Physical Examination  
BP 130/80 mmHg, Heart rate 75 bpm, Respiratory rate 12
Lungs: clear. 
Cardiac exam: Nondisplaced PMI, RRR, No murmurs
Abdomen: Normal BS, benign. 
Extremities: No edema, intact pulses

Initial Laboratory Data
BUN/Cr  13/0.8
CBC normal
TnI  10.8 ng/ml
CK-MB 2.2 ng/ml

Acute echocardiogram: Normal left and right ventricular systolic function, normal WM, no significant valvular abnormalities

Because the patient was symptom free and hemodynamically stable, she was admitted to the CCU.
Repeat cardiac markers three hours later:
TnI  10.2 ng/ml
CK-MB 2.1 ng/ml

Markers the next morning:
TnI 10.7 ng/ml
CK-MB 1.7 ng/ml

The most likely cause of the patient’s elevated TnI is:

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