Clinical introduction

A 71-year-old woman with no prior history of arrhythmia presented to the emergency room after experiencing a pounding discomfort in her left chest and back for 12 h. There were no symptoms or signs of overt heart failure. Her ECG showed new-onset atrial fibrillation with a ventricular rate of 122 bpm and non-specific ST-T wave changes. Laboratory investigations revealed a markedly increased serum troponin I level of 5.48 ng/mL (normal range 0–0.12 ng/mL) and a creatine kinase-myocardial band isoenzyme (CK-MB) level of 6.8 ng/mL (normal range <3.8 ng/mL). The rest of her blood work, including complete blood count, creatinine, serum glucose and thyroid-stimulating hormone, was unremarkable. Her chest X-ray did not demonstrate any evidence of pulmonary oedema. The patient's heart rate slowed following the administration of intravenous metoprolol, and she spontaneously converted back to a sinus rhythm after a few hours. Her serum troponin I level increased further to 6.86 ng/mL 8 h after her initial measurement. Due to the significant elevation in the …