Review Question - QID 109638

A 75-year-old male presents to the emergency room complaining of chest pain. He reports a pressure-like “crushing” sensation over his sternum. His past medical history is notable for diabetes, hyperlipidemia, and hypertension. He takes aspirin, metformin, glyburide, rosuvastatin, and enalapril. The patient drinks socially and has a 40 pack-year smoking history. His temperature is 99°F (37.2°C), blood pressure is 150/85 mmHg, pulse is 130/min, and respirations are 24/min. On exam, the patient is diaphoretic and has notably increased work of breathing. An electrocardiogram is shown in Figure A which demonstrates abnormalities in the isoelectric portion of the QT interval in several leads. Which ion channels are normally open during this phase of the cardiac action potential?