Case : Approach to palpitations A previously healthy 18-year-old boy presents for the evaluation of palpitations and lightheadedness, which started after he drove home after finishing his regular work shift. His symptoms were relieved partially by vomiting but then reappeared and worsened progressively, leading to diaphoresis and dizziness, after which he has been brought to an ED. There is no history of fever, diarrhea, intake of coffee or caffeinated beverages, or use of illicit drugs. On arrival, his temperature is 37°C; heart rate, 180 beats per minute; respiratory rate, 22 breaths per minute; blood pressure, 100/50 mm Hg; and oxygen saturation, 99% in room air. His weight is 99 kg (>95th percentile), height 184 cm (75–90th percentile), and BMI, 29.2. He is uncomfortable due to the palpitations, but he is able to follow commands. His cardiac examination reveals tachycardia, regular rhythm, normal first and second heart sounds, no murmurs, and equal peripheral pulses. His breath sounds are clear bilaterally. There are no signs of injury or trauma. Family history is negative for any sudden cardiac deaths, arrhythmias, or structural heart disease.
