A patient in their 60s presented to the hospital with sudden loss of consciousness and foaming at the mouth. The patient had no history of arrhythmias. There was no family history of sudden unexpected death or fatal cerebrovascular accident. The patient’s temperature was 36 °C, heart rate was 124 beats/min, and blood pressure was 55/32 mm Hg. Pulse oximetry showed arterial oxygen saturation of 99% on room air. Both pupils were 3 mm in diameter and reactive to light. The patient’s skin was cool, moist, and cyanosed. Lung fields were clear and heart sounds could not be distinguished due to tachycardia. The initial serum troponin T level was 6.06 ng/mL (to convert to µg/L, multiply by 1; normal range, ≤0.02 ng/mL), brain-type natriuretic peptide was 2542 pg/mL (to convert to ng/L, multiply by 1; normal range, <400 pg/mL), and D-dimer was 0.51 µg/mL (to convert to nmol/L, multiply by 5.476; normal range, 0-0.55 µg/mL). The patient’s electrocardiogram (ECG) on admission is shown in the Figure, A.