A 78-year-old woman with a history of QT prolongation presents to the hospital with fever, cough, and infiltrates on chest X-ray consistent with healthcare-associated pneumonia. Her home medications include hydrochlorothiazide for hypertension. Vital signs on admission: temperature 38.6°C, blood pressure 118/74 mmHg, heart rate 96 bpm, oxygen saturation 91% on room air. Laboratory studies show potassium 3.2 mEq/L (normal 3.5-5.0) and magnesium 1.6 mg/dL (normal 1.7-2.2). Baseline ECG shows QTc interval of 475 ms. The patient is started on azithromycin for empiric respiratory coverage. On hospital day 3, repeat ECG reveals QTc prolongation to 540 ms, and the patient develops polymorphic ventricular tachycardia ("torsades de pointes") documented on telemetry. Which of the following best explains the mechanism of this cardiac arrhythmia in this patient?

1. A)Azithromycin increases hepatic metabolism of potassium-sparing diuretics, worsening hypokalemia
2. B)Azithromycin inhibits the hERG potassium channel, delaying cardiac repolarization and creating early afterdepolarizationsGABARITO
3. C)Azithromycin competitively blocks magnesium absorption in the gastrointestinal tract
4. D)Azithromycin increases intracellular calcium influx through L-type calcium channels, enhancing automaticity
5. E)Azithromycin directly depolarizes the cardiac membrane by blocking the Na-K ATPase pump