A 50-year-old woman with a history of essential hypertension and depression was admitted to a telemetry unit because of 2 episodes of syncope within a 48-hour period. There were no other symptoms. Her blood pressure was 130/78 mm Hg, and findings on chest radiographs were normal. The serum potassium level was 3.3 mmol/L. The patient was being treated with clarithromycin for an upper respiratory tract infection. Her other medications were hydrochlorothiazide, fluoxetine, and a potassium supplement. A rhythm trace was recorded (Figure 1).

  1. Which of the following apply to the arrhythmia in Figure 1?

    • sinus with paroxysmal ventricular tachycardia

    • torsades de pointes

    • electrocardiographic artifacts

    • prefibrillatory ventricular arrhythmia

    Transient episodes of the arrhythmia recurred: 2 episodes deteriorated to ventricular fibrillation and required defibrillation. A 12-lead electrocardiogram during regular sinus rhythm was obtained (Figure 2).

  2. The trace in...

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